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273A User Manual 02_02 - Princeton Applied Research

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1. 2 FUNCTION key 30 FUNCTION SEE ESE pa ILLE 30 FUNCTION 10 REINITALIZE SYSTEM 30 FUNCTION 17 CURRENT INTERRUPT PERCENT CORRECTION 0 2 31 61 FUNCTION 11 PRINT OUT INSTALLED OPTIONS1 FUNCTION 12 ENTER LOG REFERENCE 31 FUNCTION 13 ENTER INTERRUPT 31 FUNCTION 14 OUTPUT TIME CONSTANT 31 FUNCTION 15 PEN DELAY 31 FUNCTION 16 AUTO LIMIT 31 FUNCTION 18 FIRST EXTRAPOLATION POINT32 FUNCTION 19 SECOND EXTRAPOLATION se RE Va OR ahaha 32 FUNCTION 20 IOFFSET VALUE PRESENT 32 FUNCTION 21 CALIBRATE 273A 32 GALVANOSTATIC MODE 38 GO TO LOGAL iese Ahhh 35 GPIB OR AR N Ek 12 HALF CYCLE maana hahahah hh ates 36 High Speed Mode 38 High Stability Mode o o oooo o 38 HOLD CONTINUE key 36 HOLDING indicator 36 MONITOR see sere Ge e eta 13 I MONITOR connector aasa aa 43 Overload RAR RE RE GR Ge ER Ge N ENEE 27 da OR N pater eet 12 IEEE 488 GPIB Interface Pinout 57 IEEE 488 GPIB INTERFACE 13 51 Initial Checks INTRODUCTION 21 Procedure 22 Requirements amp Setup 21 INSPECTION aa ER NGA pirate 3 A OE pia 18 INTERFACE Group 35 Interrupt Frequency LL 31 LOFFSET mana AA 32 IR Compensation 00000ae 12 18 IR Compensation Extrapolation 32 IR COMPENSATION
2. key reverses the polarity of the expression and can be pressed at any point before ENTER is keyed b To set and enter a Vertex Current of 1 mA when operating on the 100 mA range key E I 2 0 1 ENTER Since the desired current 1 mA is 1 of the selected Current Range 100 mA E I 1 is set to 01 2 DELAY 1 and DELAY 2 These keys are used to specify delay values There are two delays The first DELAY 1 precedes the scan The second DELAY 2 can be interposed between the first and second legs of the scan Delays can be specified as a time interval seconds or as a drift rate mV s Delays can also be PASS ed in which case the delay is minimum 4 ms If specified as a time interval the range is 1 s to 100 000 s and the delay can be done with the cell either ON or OFF CELL OFF a key in the SETUP group not to be confused with CELL ON in the CELL group determines whether the delay will be performed with the cell ON or OFF Each time the key is pressed it toggles between the two setup states as indicated in the display If the cell is OFF during the delay no potential or current is applied If it is ON potential or current as appropriate is applied If the intent is to postpone starting a scan until the open circuit cell potential settles the delay is specified in mV s Typically the potential drifts rapidly at first and then more and more slowly as it asymptotically approaches its final value The
3. The EXTERNAL INPUT is controlled by the EXT ON key When pressed the associated indicator lights and the Model 273A becomes responsive to potentials applied to the EXT INPUT connector If pressed again the indicator goes out indicating that potentials applied to this input will be ignored 5 2 10 FILTER Group This group contains two indicators and a key The key allows the user to select OFF no filter or LOW PASS low pass filter selected The indicator corresponding to the filter status will always be lighted The low pass filter has a sharp cutoff at 5 3 Hz A 590 Hz low pass filter is also available under software control from the back panel It is often helpful when making low current measurements on large electrodes because it reduces the noise at the OUTPUT connector The disadvantage of using the filter is that the Output response time is degraded The filter has no effect on MONITOR output Use of the filter for galvanostatic operation is not recommended It may be advantageous to synchronize data acquisition with the power line frequency when filtering This can be done using Override 14 if desired The use of Override 14 is described in Section 5 2 4 5 2 11 IR COMPENSATION Group Introduction There are three keys and two indicators in this group Positive Feedback IR Compensation is selected by pressing the POSITIVE FEEDBACK key Current Interrupt IR Compensation is selected by pressing the CURRENT INTERRUPT key Both
4. 27 Scan Status Display o o ooo oo 27 SCANNING indicator oo o o o o o o 36 SENSE 8 WORKING ELECTRODE JACKS 52 SETA OFFSET KEY sia 48 SINGLE CY GLE maana aba 37 SPECIFICATIONS Battery Backup 12 Current Measurement 11 IR Compensation 12 Potential Current Control 11 Power Amplifier 11 Power Requirements 12 Rack Mounting 12 SIZE paaa T 12 System ii EE Ee o 12 tel os 12 ae AA AE HE IE EA 35 Appendix A Pinouts STABILITY versus SPEED 38 START key Li 27 Static Discharge ee ee ee 10 STEP key 27 STOP key 36 TALK aka Bah RR BREER EER ie hh fide hated 35 Time Constant 31 TRANSIENT SENSITIVITY 9 Transient Sources 0 0 00 cece eee 10 Update Coulombs 00 eee aa 32 VENTILATION 020 8 Weight Li 12 t and 2 a 33 BERE MEEL o ee Peet rs 33 Pa AG RP AA 33 1 YES and 2 NO 33 ENTER LL 34 EXP SR EER ARE PAPA oto eR 33 HOLD CONTINUE a 36 MV SEC eee nee 34 SEC LL 34 START LL 36 STEP 33 1 and HE 2 cee eee eee 33 63 64 Model 273A Potentiostat Galvanostat User s Manual
5. However there is finite leakage across this solid state switch when the cell is OFF Hence the third switch the Cell Relay shown in the figure Although this relay is much slower than the solid state switch its low leakage assures a very high degree of cell isolation Both the manually operated Cell Enable switch and the computer controlled solid state switches relay and solid state switch provide a feedback path for the Control Amplifier when the cell isn t connected The gain in this path is nominally X1 solid state switch or X1 5 relay If one volt is applied the Control Amplifier output will be 1 V or 1 5 V as appropriate Model 273A Potentiostat Galvanostat User s Manual Notes 1 All switches shown in o rectangulor box are digitally controlled 2 For simplicity buffer amplifiers ore shown without associated gains interface to Remote Computer or to Model 273 CPU Mondor Clectrometer Ry 1 SPPRESSION 28000 COUNTS 42008 MAL SON CURRENT ANALOG TO DIGIAL CONVERSION ne tiov lt 42000 COATS 1 t Ma 7 i SITO Om INTEGRATOR Ng Buller Aus A D Signo Fig 3 Model 273A Simplified Block Diagram Chapter 3 Characteristics 17 3 2 6 IR Compensation There are two modes of IR Compensation Current Interrupt and Positive Feedback When Current Interrupt is enabled the IR COMP DAC applies the correction voltage derived as a fraction of the 10 24 V reference Note that the sw
6. the record will be marred Function 15 determines when the pen will drop The range is 0 to 10 seconds and the default value is 0 5 seconds The amount of delay required will depend on the recorder FUNCTION 16 AUTO LIMIT This function sets the most sensitive current range to which the Model 273A can automatically range auto ranging active The range is O 1 A to 7 100 nA The default value is 6 FUNCTION 17 CURRENT INTERRUPT PERCENT CORRECTION This function sets the percent of correction applied in Current Interrupt IR Compensation The range is 0 to 200 The default value is 100 Chapter 5 Operating Instructions 31 32 FUNCTION 18 FIRST EXTRAPOLATION POINT This function sets the first of the two times used to do the correction extrapolation in Current Interrupt IR Compensation The range is 2 to 1997 The default value is 10 us on the 1 A range and on the 100 mA range It is 75 us on all other ranges Note The sum of the values of Functions 18 and 19 must be lt 1999 us FUNCTION 19 SECOND EXTRAPOLATION POINT This function sets the increment from the first time to do the correction extrapolation in Current Interrupt IR Compensation The range is 2 to 1997 The default value is 10 us on the 1 A range and on the 100 mA range It is 75 us on all other ranges Note The sum of the values of Functions 18 and 19 must be lt 1999 us FUNCTION 20 IOFFSET VALUE PRESENT This function reads the IOFFSET value present unli
7. 482 4411 801 S Illinois Avenue FAX 865 483 2133 Oak Ridge TN 37831 ATTN Customer Service D CUSTOMERS OUTSIDE OF U S A To avoid delay in customs clearance of equipment being returned please contact the factory or the nearest factory distributor for complete shipping information Copyright 2002 Advanced Measurement Technology Inc All rights reserved Princeton Applied Research is a registered trademark of Advanced Measurement Technology Inc All other trademarks used herein are the property of their respective owners TABLE OF CONTENTS Safety Instructions and Symbols SERE BERE PAPA PRES PARE DEE PERE OE EERE ROE Rees ee REPRE DNA vi Cleaning Instructions EES RE eis BALA NA NG ANA LG DE EE DEER EDE EER RE EE DE EE ED pee ae Vi 17 INTRODUCTION ee es SS ine WE NG RE NG OS RE RE NG EE RE EE RE EE RE EE DE EE RE EE SEE ee eS ix AE IR COVE Ka AE ED ER a SE ag OR I Ss Ee EE ER EE OE EE KAL CL in ER EE 1 1 2 Aboutthis Manual SERE lo DEAR EE ERA pale GERED SERE REED SERE EER DS EEE DEES BERE 1 163 gt Controlling the Model 273A KERSE EE sesh eee eee hee eee eee eee eee Eee eee EE ESP eee EES 2 1 4 Polarity COnVention sso BEE prep Gee eS eh BASE BEE SEES EERE DEES EERE Dees REDE 3 1 5 Inspection of New Instrument se cotorra terrano eee eee eee eee ee REE ESS eee Eee eS eee RE 3 1 6 Maintenance and Service so 00000 SERE be ek EE RE DE DE EE EE SEER EE ES EE DEER RE SE EEE EEE TEER EE 3 2 SAFETY CONSIDERATIONS is se po
8. Group 40 IR Compensation techniques 40 Lightning amma N EE 10 Line FUSES aa oe ee Ee ge Ge ee ER SE 5 Line Voltage Selector Card 6 Linear ER AE EE 13 LINEAR indicator o oooooooo 23 LISTEN RE ER ER 35 LOCAL key oes does GE eie eg ie Ge GR et 35 LOCAL LOCKOUT 2 a 35 AN 13 LOG Indicator 0 0 00 cee eee 47 Log Reference EE Ee ee 47 LOW PASS filter anG 47 Maintenance 3 MEASURE ONLY MODE 38 Metric Hardware 14 MOD DAG rile ei 15 MODE GIOUP strie 38 MODEL 407A INTERFACE 14 Multiplexed Ouput connector 14 MULTIPLEXED OUTPUT 51 62 MV SEC key Li 34 NUMERIC KEYPAD a 33 OFF Output Mode 44 Offset Display 0 ccc eee eee 32 OPERATING MODES 38 Operation 24 FRONT PANEL 25 INTRODUCTION 25 OUTPUT 70x00 ES LAKE and 13 OUTPUT and AUX DIGITAL Connector 18 OUTPUT Group EE EE ee ee ee 47 Output Mode eee ee eee 47 COULOMBS 47 LINEAR 47 LOG kaa ASE ER 47 OFF nip siete Ala DALL bites 47 OUTPUT TIME CONSTANT 31 Overload LL 27 OVERRIDE 00 e eee eee 32 OVERRIDE 10 OFFSET DISPLAY 32 OVERRIDE 11 UPDATE COULOMBS 32 OVERRIDE 12 CORRECT DISPLAYEDE 32 OVERRIDE 13 CELL OFF AT END 32 OVERRIDE 14 LINE SYN
9. Option Chapter 3 Characteristics 19 20 Model 273A Potentiostat Galvanostat User s Manual 4 INITIAL CHECKS 4 1 Introduction The following procedure is provided to facilitate initial performance checking of the Model 273A Perform this procedure after you have inspected the instrument for obvious shipping damage Any damage noted should be reported to the carrier and to Princeton Applied Research Be sure to save the shipping container for inspection by the carrier If you have not used a Model 273A or 273 before this procedure also will help acquaint you with the operation of the instrument The Model 273A is checked using a resistor as the cell These checks are adequate for determining that the instrument is functioning normally Note that these procedures are not intended to demonstrate that the instrument meets specifications but rather to demonstrate that it has arrived in good working order Each Model 273A receives a careful checkout before leaving the factory and ordinarily if no shipping damage has occurred it will perform within the limits of the specifications If any problems are encountered in carrying out these checks contact the factory or the factory authorized representative in your area for aid 4 2 Required Equipment 4 3 Setup Other than the Model 273A to be checked and its electrometer no other equipment is required 1 Set the Model 273A with electrometer on a lab bench Or if you prefer moun
10. Programming Command Handbook Model 273A Potentiostat Galvanostat User s Manual This signal controls the Model 303A s Stir function in response to commands from an external computer The underlying assumption is that the Model 303A is being used with a Model 305 Stirrer A 4 IEEE 488 GPIB Interface IFC 12 SHIELD 14 DI06 15 DIO7 16 DI08 17 REN E E 3 gt 2 5 a Dos Chapter 5 Operating Instructions 57 A 5 RS 232C Interface FUNCTION COMMENT Earth Ground Ties the chassis of the 273A to that of the computer Transmit The 273A transmits on this line lt must connect to the computer connector Data pin that receives serial data Receive Data The 273A receives data on this line It must connect to the computer connector pin that transmits serial data Request to This line is permanently asserted in the 273A that is it is always at a positive logic level 12 V As a result the computer continuously receives the message that the Model 273A is ready to receive a character 5 Clear to Send The computer controls the 273A via this line To enable the 273A to transmit the line is placed at the positive logic level 3 V to 12 V To hold off transmission by the 273A the line must be at the negative logic level 3 V to 12 V Once this line goes positive data transfer if initiated by an appropriate command will proceed rapidly This line is pulled up to 12 volts so that if it is left uncon
11. The protection is likely to be impaired if for example the apparatus 1 Shows visible damage 2 Fails to perform the intended measurement 3 Has been subjected to prolonged storage under unfavorable conditions 4 Has been subjected to severe transport stresses The instrument should not be used until its safety has been verified by qualified service personnel 2 6 Ventilation The Model 273A incorporates forced air ventilation to maintain a safe operating temperature Thus it is necessary to allow some free space minimum 10 cm behind the instrument so that adequate air circulation can occur Moreover there must be adequate circulation between the space behind the instrument and the general laboratory circulation to allow effective cooling Ina typical installation these requirements are satisfied with a large safety margin If the Model 273A is cabinet or rack mounted some additional effort to assure adequate ventilation may be required Ambient Temperature From 10 C to 40 C The instrument shall operate from 10 C to 40 C but may not meet some temperature related specifications The instrument shall operate from 20 C to 30 C and meet all its specifications over this range The ambient temperature should not exceed 45 C 113 F 2 7 This Apparatus as a Source of Radio Frequency Interference In a typical application it is unlikely that this apparatus will act as a source of noticeable radio frequency interference Howe
12. V Range Galvan 200 20 00 and 2 000 of full scale current Accuracy Applied Potential 0 2 of reading 2 mV Applied Current 0 2 of full scale current 11 3 1 5 IR Compensation 1 Positive Feedback Digitally Controlled Range 1 Current Range 0 to 2 times the Current Range Resistor Resolution 0 05 of Current Range Resistor 2 Current Interrupt Digital Potential Error Correction 12 bit DAC Total Interruption Time lt 200 us Switching Time ON OFF lt 1 us 1 KO resistive cell 3 1 6 System 1 Rise Time 10 to 90 on high speed setting No Load lt 750 ns 10 1A lt 3us 10 KO 100 HA lt 2 us 2 Noise and Ripple typically lt 25 uV rms referred to external input 3 1 7 Computer Interfaces 1 RS 232C 2 IEEE 488 GPIB The instrument recognizes more than 100 different commands for control from a remote computer via the IEEE 488 or RS 232C interface The Model 273A Remote Programming Command Handbook describes these commands and provides detailed explanations of GPIB and RS 232C communications including rear panel switch settings and communications protocols 3 1 8 Weight 31 kg 68 Ib 3 1 9 Size 48 cm W x 30 cm H x 51 cm D 19 W x 12 H x 20 D 3 1 10 Power Requirements 100 130 V or 200 260 V 50 60 Hz 350 watts maximum 3 1 11 Rack Mounting The Model 273A may be mounted in a standard 19 inch 47 5 cm rack assembly If rack mounted the Model 273A must be supported to avoid excessi
13. a aa 47 Manual 47 Cycle Control Key 36 DEFECTS AND ABNORMAL STRESSES 8 DELAY 1 and DELAY 2 key 28 DELAY 1 indicator 23 DELAY 2 indicator 24 DIFFERENTIAL ELECTROMETER 1 11 16 51 Differential Electrometer 16 Display si ES IAS 25 E Monitor TER DAY id ds aaa 13 46 E MONITOR connector 40 E Overload RESESSIE a ESE SES ER EI Ti 8 E I 1 indicator oooooo 23 E l 1 2and 3 keys cs EE RA 28 E I 2 indicator oooooo 24 El ER Se EE An in fi ig ito da do ee 28 E I 3 indicator o o ooo 24 E APPEED ie cits to ts AA tate tes 37 EEC Publication 348 5 electrometer ROLE Bad Sea eee NDN 51 Cell Cable Leads 52 Cell Switch 52 Reference Electrode Jack 52 Sense and Working Electrode Jacks MATE ER a 52 Working Electrode Jack 52 Electrometer Cell switch 8 ELECTROMETER MONITOR 13 50 Electrometer Monitor connector 40 ERROR gioelisa thee ED Ee 35 EXP KEY ti ER ER NE 30 EXT INPUL wer a 12 15 40 EXTON OY ie Seed GESE EER EP Ee es 40 External Input connector 39 FILTER Group 40 FILTER LOW PASS 40 Filt OFF vil rn e 40 Front Panel 0 0000000008 25 Front Panel Connectors 12 Front Panel Controls
14. any hardware removed from the chassis the cable connectors and attached equipment Model 273A Potentiostat Galvanostat User s Manual The differences between metric and American Standard hardware are not always easily recognized As an aid metric hardware is marked with a yellow chromate finish or in the instance of metric screws with a yellow locking pad applied to the threads 3 2 Internal Organization 3 2 1 Introduction Although the Model 273A is a complex instrument its basic organization is straightforward as depicted in Fig 3 The following paragraphs discuss the Model 273A as represented in the figure in some detail The symbols used in Fig 3 are for the most part conventional and require no description However it should be noted that the many switches drawn inside rectangular boxes are digitally controlled switches and not under direct mechanical control The gains and scaling of internal signals are omitted for the sake of clarity 3 2 2 Bus Referring to Fig 3 notice the bus that interconnects all of the major circuit blocks All of these blocks communicate with each other and with the controlling microprocessor via this bus This is true both for control via the front panel and for control from an external computer via the GPIB or RS 232C port 3 2 3 Applied Potentials and Currents Note the Control Amplifier located near the center of the figure As shown many different signals are applied to the input o
15. but the CELL ENABLE switch is OFF FULL BRIGHT Both the CELL key and the CELL ENABLE switch are ON The cell is ON only when the light is at full brightness The Model 273A is controlled even when the cell isn t ON that is having the Cell OFF does not cause an overload condition In the context of this discussion CELL ON and CELL OFF refer to the path from the Control Amplifier output to the Counter Electrode cable lead The red indicator does not respond to the status of the actual counterelectrode connection That connection could be secure or faulty and it would have no effect on the red indicator which responds only to the CELL ON switch the CELL ENABLE switch and on the governing software However if the Cell is ON and there is no connection to the counter electrode the effect will be the same as if the cell had infinite resistance and an E OVERLOAD indication will occur 5 2 9 INPUT Group This group contains one indicator one key and one BNC connector Together they provide the means for summing external control potentials with those generated in the instrument or transmitted to it from an external computer via the rear panel RS 232C or GPIB port The external control potential is applied to the EXTERNAL INPUT connector In potentiostat operation voltages from 10 V to 10 V can be applied In galvanostat operation the range is 2 V to 2 V corresponding to 2 times the full scale current except on the 1 A Current Range wh
16. change could be a problem in some situations it will usually be relatively minor The real problem occurs when shifting to a more sensitive range For instance if in the example the current range were to shift to 10 pA where the resolution limit is 100 Q the actual programmed resistance will become 1200 because the value can only be represented to the nearest 100 Q In other words the error will now total 34 Q Similarly a further shift to 1 yA would give a resistance of 1000 Q 234 O error and a shift to 100 nA would give a resistance of 1000 Q 1234 Q error Note Should one later shift to less sensitive ranges the error will be successively reduced with each current range step Clearly operators need to be mindful of the resolution limit for the setup current range and should key a resistance appropriate to that limit Also if more sensitive ranges are used during the experiment users will have to be mindful of the impact the changing resolution will have on the programmed resistance and of the possible consequences of large resistance errors Two procedures for establishing positive feedback compensation are provided The first procedure applies when the value of R is known The second applies when A is not known 1 R KNOWN a Press SET IR The current value of assumed R will be displayed b Key the value of R to be compensated and press ENTER The new value will be displayed c Press POSITIVE FEEDBACK The as
17. connector This output tracks the current linear or log or transferred charge coulombs The output impedance is 1 kQ In the linear mode the output range is 2 V 1 V full scale In the other modes it is 10 V Note that the voltage at this connector is derived from a 12 bit digital to analog converter that is updated each time the applied potential or current changes These updates may be marked by the presence of moderate digital switching transients at this output For best results use the MONITOR output to track current unless use of the low pass filter is desired 2 COULOMBS LINEAR LOG These three lights indicate the output mode as selected by the associated key There is additionally a fourth mode OFF established when the other three indicators are extinguished The output in each mode is as follows a OFF 0 Vis present at the OUTPUT connector b LINEAR The voltage varies linearly with the current A full scale current gives 1 V out The maximum output as dictated by the maximum current is 2 V corresponding to a current of two times the selected current range 1 V maximum on 1 A range Low currents on a fixed current range may show the stepped response of a digitally reconstructed signal c LOG The voltage varies with the log of the current A current equal to the Log Reference Range Function 12 Section 5 2 4 gives O V out The transfer function is 1 V per decade consistent with the constraint that the output ca
18. current and the offset range is 2 times the full scale range in effect at the time OFFSET is set Note that the offset function only affects the level at the OUTPUT connector identically the Y Axis Recorder Output It is functional for all three output modes LINEAR LOG and COULOMBS The displayed cell current is not affected unless Override 10 see Section 5 2 4 is placed in the YES state fn i Warning For operator and equipment safety the power should be off when connecting or disconnecting cables Model 273A Potentiostat Galvanostat User s Manual Fig 8 Model 273A Rear Panel 5 3 1 Cell Interface The cell cable mates with this 36 pin connector The connections include shields and grounds the electrode connections and power for the Differential Electrometer Assembly The hard wired cable from the Differential Electrometer Assembly mates with this connector Warning To prevent dangerous possibly lethal electric shock always have the front panel cell enable switch in the off position when handling the clip leads at the end of the electrometer assembly Voltages as high as 100 V at currents as high as 1 A could be present 5 3 2 Recorder Interface This 15 pin D type connector is provided for interfacing between the Model 273A and a Princeton Applied Research RE0150 or RE0151 recorder Connections include a Y axis drive same as the front panel OUTPUT signal an X axis drive same as the front p
19. either a logic O or a logic 1 default is logic 0 according to the operand of the last applied TRIG command TRIG 0 establishes a logic 1 baseline TRIG 1 establishes a logic 0 baseline Once a logic 0 baseline is established subsequent TRIG 1 s will cause a 10 to 20 ms wide logic 1 pulse to be generated Similarly once a logic 1 baseline is established TRIG 0 s will cause a 10 to 20 ms wide logic 0 pulse to be generated 5 BIT 0 IN The level on this line will be read and reported to the host computer if the command BIT 0 is applied 5 V 5 V at up to 100 mA is available for external use BIT 0 OUT If Current Interrupt IR Compensation is NOT active the level on this line will be set to a logic 0 if the command BIT 0 0 is applied It will be set to a logic 1 if the command BIT 0 1 is applied If Current Interrupt IR Comp is active this line will go high about 3 us before the start of the current interruption and will go low about 7 us after the start of the current interruption This pulse can be used to trigger an osciloscope so that the IR Current Interrupt waveform can be easily monitored at the rear panel ELECTROMETER MONITOR connector When operating a Model 273A with a Model 303A SMDE via a Model 307 Interface this signal PURGE controls the Model 303A s purge function in response to commands from the external computer The computer initiates a purge by applying a PURGE command see discussion of this command in the Model 273A Remote
20. electrochemical impedance systems 5 3 10 AC Input This connector used only in units equipped with the 273A 92 Electrochemical Impedance Interface option accepts a sine wave input from an external oscillator such as that supplied by a Princeton Applied Research lock in amplifier The nominal frequency range is 50 uHz to 100 kHz although this is dependent on cell impedance Input voltage must be no greater than 5 volts rms This signal can be used to modulate the signal sent by the Model 273A to the cell and can be attenuated as desired It is controlled by commands from an external computer via the GPIB or RS 232C port refer to the Model 273A Remote Programming Command Handbook 5 3 11 273A 92 Electrochemical Impedance Interface Option The 273A 92 Electrochemical Impedance Interface option previously called the AC Interface option is intended primarily for use with Princeton Applied Research electrochemical impedance systems but can also be used for ac voltammetry applications This option is designed to allow superposition of an externally generated ac excitation signal on the dc signal generated by the Model 273A The externally generated ac signal is input at the AC INPUT connector and is combined with the signal generated by the Model 273A before it is applied to the cell The 92 option board has three output connectors AC OUTPUT AC E OUTPUT and MULTIPLEXED OUTPUT Software commands control both the mode of output I E or
21. electrode is used connections between the Auxiliary Interface and the Model 303A are made via the Model 307 Interface This accessory allows the Model 273A to be used in conjunction with the Model 303A Static Mercury Drop Electrode by providing three cables all hard wired to the Model 307 to make the necessary connections One cable connects to the Model 273A AUXILIARY INTERFACE connector the second connects to the Model 273A CELL INTERFACE connector and the third connects to the Model 303A INPUT connector A 0 1 A fast blow fuse is provided in the Counter Electrode line The Model 307 requires externally supplied 24 V at 1 A Ed SIGNAL FUNCTION BE EXT TRIG This input allows an operation in progress to be halted via the WFT command from an external computer If the command WFT 0 is applied operation will resume when a logic 0 is applied to the EXT TRIG line If the command WFT 1 is applied operation will resume when a logic 1 is applied tot he EXT TRIG line Tae In applications where the Model 273A is being used with a Model 303A via a Model 307 Interface DISPENSE this signal causes the Model 303A to do a Dislodge Dispense operation on command from an external computer The computer initiates the dispense operation by applying a DISP command see description in the Model 273A Remote Programming Command Handbook TRIG OUT A TTL trigger output is provided on this line on application of the TRIG command The Trig Out baseline is
22. four screws supplied with the kit as well as the eight screws that became available when the original side panels were removed This completes the procedure The 273A can then be mounted in any standard rack and secured with standard rack mounting screws not supplied Because of the Model 273A s considerable weight we strongly recommend that it be supported to prevent excessive stressing of the front panel One way of providing the necessary support is to set the Model 273A on a rack mounted shelf or drawer 59 60 Model 273A Potentiostat Galvanostat User s Manual 1 YES and NO key 32 DIA saaan KA KARA NAWA kaa 14 19 31 51 2ISA 92 0pton iii Ree ADAN 14 WA SERS ARA Re Re BEES BERE 13 14 50 56 ADTA EA TR IE ARAB ER GEER BE SA 14 ACEOUTPUT 14 50 ACE Output Connector 005 50 ACIOUTPUT 13 50 AC Output Connector 50 AG INPWE is EE SE 25 RR BEA Bes Res BEDE 51 AC INPUT connector 51 ACCESSOMES 2 0 pi SS RES BESS Na 14 Accessories Catalog 14 AD zz oe Re Rae BERE EE BEG 18 ADVANCE key i 36 AUTOLIMIT LL 31 AUX A D connector 50 AUX A D INPUT 13 50 AUXILIARY INTERFACE 13 50 AUXILIARY INTERFACE connector 56 Battery Backup 12 BIAS DAC 02220 15 Buffer Amplifier Measurement Circuit 15 BUS ees namana eee ND eR ee bee 15 Calibrati
23. ground Many recorders have a pen drop circuit configured such that the pen drops when the closure occurs 5 3 3 Auxiliary Interface Various miscellaneous functions are provided by this connector including 1 Ground 2 5 V 20 mA maximum sufficient for pullups 3 Signals for interfacing to the Model 303A SMDE PURGE STIR and DISLODGE 4 Various inputs and outputs controlled by commands applied via the GPIB or RS 232C ports See Appendix A for more detailed information 5 3 4 Power Amp Monitor The output of a 10 1 attenuator connected to the Counter Electrode potential is provided at this connector The output impedance is 1 kQ 5 3 5 Aux A D Input This high impedance gt 10 Q input provides an external input to the A D Converter This input allows users to track any experimental variable that has an analog voltage output in the range of 10 V For example with the appropriate ancillary instrumentation not available from Princeton Applied Research a user might track temperature pH optical absorbance or mechanical displacement One specific use for this input is in making galvanic corrosion measurements with the Model 332 Corrosion Measurement System Note that there is no way of reading the applied level from the front panel A reading can be initiated only via commands applied to the rear panel RS232C or GPIB ports 5 3 6 Electrometer Monitor The output of the differential electrometer is available at this c
24. is 1 kQ Linear Tracks MONITOR output 1 V for full scale current 2 V maximum Log 1 V per decade 10 V maximum A current equal to the Log Reference Range selected by Function 12 gives 0 V out Coulombs 10 V Initial sensitivity is one full scale current for one second gives 10 V out Sensitivity decreases by factor of ten at 10 V Sensitivity ranging repeats as required to accommodate total charge Bipolar 3 1 14 Rear Panel Connectors 1 2 CELL INTERFACE Connections to cell are made with provided cable via this connector POWER AMP MONITOR Amplifier output divided by ten 100 V range of amplifier output gives 410 V POWER AMP MONITOR output Output impedance is 1 KQ ELECTROMETER MONITOR Output of the differential electrometer Not corrected for IR drop unlike front panel E MONITOR output Output impedance is 1 kQ AUXILIARY INTERFACE Provides triggers and Model 303A control signals Note that the Model 303A is not cabled directly to this connector It rather is cabled to the Model 307 Interface which in turn is cabled to the AUXILIARY INTERFACE connector AUX A D INPUT 10 V high impedance analog input useful for galvanic corrosion spectro electrochemical and other measurements Input impedance gt 10 Q RECORDER INTERFACE 15 pin connector provides Y output identical to front panel OUTPUT signal X output identical to front panel E MONITOR signal contact closure lines for pen up down contr
25. is compatible with TTL as described in Appendix A Model 273A Potentiostat Galvanostat User s Manual 3 2 10 273A 92 Electrochemical Impedance Interface Option The 273A 92 Electrochemical Impedance Interface option previously called the AC Interface option is intended primarily for use with Princeton Applied Research electrochemical impedance systems but can also be used for ac voltammetry applications This option is designed to allow superposition of an externally generated ac excitation signal on the dc signal generated by the Model 273A The externally generated ac signal is input at the AC INPUT connector and is combined with the signal generated by the Model 273A before it is applied to the cell see Fig 4 The 92 option board has three output connectors AC OUTPUT AC E OUTPUT and MULTIPLEXED OUTPUT Software commands control both the mode of output I E or multiplexed as well as the type of signal applied full ac dc signal or ac signal only Multiplexing is accomplished by alternating the operand of the MIE command between 1 and 2 on successive iterations The Model 273A Remote Programming Command Hanabook describes the computer commands used with the Model 273A 92 option AC DC COUPLING SELECT BUFFER OSC IN BNC PROGRAMMABLE GAIN STAGE TO POTENTIOSTAT CONTROL AMPLIFIER MULTIPLIER SO X2 0 2 X0 02 Fig 4 Simplified Block Diagram of Model 273A 92 Electrochemical Impedance Interface
26. keys are toggles for the corresponding function However only one IR Compensation mode can be active at atime If one of the two is active and the other is selected the one previously active will drop out and the newly selected mode will become active The associated indicators indicate the status of the IR Compensation modes The SET IR key is used in establishing Positive Feedback IR Compensation Note Positive feedback is not available when the Model 273A is operating in the galvanostatic mode The voltage at the front panel E MONITOR connector and at the rear panel RECORDER INTERFACE connector is corrected when either technique is employed in contrast to the voltage output at the rear panel ELECTROMETER MONITOR connector which is not corrected for the iR drop The two IR Compensation techniques are performed in entirely different ways Because the techniques each have strengths and weaknesses some situations will call for one technique and some for the other Table 2 briefly lists the relative strengths of the two techniques Both techniques are discussed in the following paragraphs Model 273A Potentiostat Galvanostat User s Manual Table 2 POSITIVE FEEDBACK AND INTERRUPT COMPARISON PARAMETER INTERRUPT POS FEEDBACK CURRENT SPEED FAST SLOW EASE OF USE MORE DIFFICULT VERY SIMPLE R TRACKING DOES NOT TRACK TRACKS STABILITY CRITICAL VERY STABLE ARTIFACTS NONE MINOR E MON CORRECTED YES YES GALVANOSTAT MODE NOT AVAILABLE AVAI
27. the manual addresses those needs Instructions for operating the unit remotely via either the RS 232C or GPIB IEEE 488 interface port are given in the separately bound Model 273A Remote Programming Command Handbook 5 2 Front Panel The Model 273A s front panel Figure 5 1 is divided into clearly delineated functional areas The SCAN STATUS DISPLAY OVERLOAD INDICATORS and ALPHANUMERIC DISPLAYS are located at the top of the panel The key indicator areas SCAN SETUP CONTROL MODE CELL INPUT FILTER IR COMPENSATION CURRENT RANGE OUTPUT and INTERFACE are located beneath them Each area s features are discussed in some detail in the following paragraphs 5 2 1 Alphanumeric Display The Model 273A incorporates an LCD alphanumeric display able to show two lines 40 characters each of both upper and lower case characters The measured potential and current are continuously displayed on the upper line Messages and parameter values appropriate to the operation being performed are displayed on the lower line For example when a setup parameter key is pressed the previously set value is displayed together with the message ENTER XXX XXX signifies the parameter The new value can then be keyed and ENTER pressed after which the new value will be displayed Pressing ENTER again clears the new value from the display so that it can return to the normal bottom line mode in which the bottom display line can scroll through several possible d
28. to make the current more catholic Making the applied current more negative will tend to make the current more anodic This sense is reversed at the front panel external input Them making the input more positive will make the cell current more anodic Making the input more negative will make the cell current more cathodic Bear in mind that the EXTERNAL INPUT is a high impedance 100 kQ input in both potentiostatic and galvanostatic operation In galvanostatic operation 1 V applied results in a full scale current 1 5 Inspection of New Instrument Newly received apparatus should be inspected for shipping damage If any is noted immediately notify Princeton Applied Research and file a claim with the carrier Save the shipping container for possible inspection by the carrier Warning The protective grounding could be rendered ineffective in damaged apparatus Damaged apparatus should not be operated until its safety has been verified by qualified service personnel Damaged apparatus should be tagged to indicated to a potential user that it may be unsafe and that it should not be operated 1 6 Maintenance and Service The Model 273A Potentiostat Galvanostat has been designed for optimum reliability and requires no periodic maintenance This manual contains no service information The Model 273A is very difficult to service in the field special fixtures and services are required that are not readily obtainable except at the factor
29. will be ON or OFF according to the state of the governing Override 8 E I APPLIED This key allows a speed constant potential current to be applied to the cell If the associated indicator is lit it means that E I APPLIED will be applied if the Cell is ON The E I Applied indicator is lighted at powerup It extinguishes when the START key is pressed to begin a scan The value for the E I APPLIED parameter is that in effect at the time the instrument was last powered down or the last value set if changed since powerup E I APPLIED can take potential values from 10 V to 10 V Current values are a fraction of the selected Current Range up to the maximum possible value of 2 1 is maximum on the 1 A range There are two ways of changing the value of E I APPLIED The simplest is to use the 1 and keys Anytime a potential current is applied these keys can be used to increment Chapter 5 Operating Instructions 37 decrement the potential in 1 mV steps or the current in 0 1 of Current Range steps If one of these keys is held down continuously the steps increase to 10 mV or 196 of Current Range allowing a large change to be achieved quickly The second way of changing the parameter s value is to specify a specific value and enter it Example To set E I APPLIED to 1 V key E I APPLIED 1 ENTER 5 2 7 MODE Group 1 STABILITY versus SPEED This subgrouping consists of two indicators and one key One of the two availa
30. Amplifier The user can do this in either of two ways If error due to IR drop in the working electrode lead is not a consideration simply connect the jumper shorting plug from the Sense jack gray to the Working Electrode jack green immediately below it When working at high currents it may well be important to eliminate IR drop error resulting from the resistance of the working electrode lead and alligator clip To do so connect a lead from the Sense jack gray directly to the Working Electrode at the cell Be sure to clip to the electrode and not to the clip at the end of the working electrode lead Attaching the sense lead to the clip at the end of the working electrode lead will still leave the IR drop in the clip itself as a source of error Sensing at the cell also prevents errors due to inductance in the working electrode lead This inductance can cause significant phase shifts Sensing at the electrometer is convenient and yields good results in many applications Sensing at the cell gives faster speed and freedom from errors due to IR drop in the working electrode lead As a general rule sensing at the cell is recommended in applications where the current will exceed 100 mA or where the equivalent cell impedance is less than 5 Q Model 273A Potentiostat Galvanostat User s Manual What this comes down to is that the user must make a decision in each application where the electrometer is being used If the decision is to ignore IR drop
31. C 33 PASS key Li 33 PEN DELAY see GE ee ee ee 31 PINOUTS coco 54 AUXILIARY INTERFACE 56 CELL INTERFACE 55 IEEE 488 GPIB INTERFACE 57 RECORDER INTERFACE 55 RS 232C INTERFACE 58 POLARITY CONVENTION 3 14 POSITIVE FEEDBACK 40 Positive Feedback IR Compensation 41 POTENTIOSTATIC MODE 38 POWER AMP MONITOR 13 POWER AMP MONITOR Connector 50 Power Amplifier 2 0000000 16 Power Cord Plug 5 Power Requirements 12 POWER VOLTAGE SELECTION 5 Rack Mounting ee eee 58 RE0150 Ee GE ee ee 14 49 REOTSI HARE ARE ES DEER DEERE E SERE REG 14 49 REAR PANEL occ 48 Rear Panel Connectors 13 RECORDER INTERFACE 13 49 RECORDER INTERFACE connector 13 46 REFERENCE ELECTRODE JACK 52 REINITALIZE LL 30 REMOTE 222 cee eee eee 35 Remote Computer Control 2 RESET INTEGRAL key 48 Religiose die Bite PRA 1 9 RS 232C INTERFACE 58 RS 232C EE EE eee 1 RS 232C INTERFACE 13 51 Model 273A Potentiostat Galvanostat User s Manual Safety Considerations 5 Safety Requirements 5 SCAN 1 and SCAN 2 keys EE Ee 37 SCAN 1 indicator 23 27 SCAN 2 Es 27 SCAN 2 Indicatori 24 SCAN SETUP Group
32. DEER SE SR EES ESE SE AE EE SE SESDE DEE aa n RE DEE RE DEER GE ELA 12 IAS N OO OE OE OE EL EL EL OES 12 3 1 10 Power Requirements is EARTH ESRA GESE SEE EE RE ESRA be eb tebe EERE TESS PERE ES 12 31 11 Rack MOUNUNG srt DES ERROR SR EER SES haus EER REDE EE RE REDE DEES ED RE 12 31 12 Battery BaekUDi MEES BREER BEE SEER GESE SEE bebe Sees be EE EERE EERE DEES PERE ES 12 3 1 13 FrontPanel Connectors x 5252552525255 555258 EE RR Seek DE RE REDE EE ROER ED RE 12 3 1 14 Rear Panel Connectors si i sha BEER eee pea eee RE SESE Ee EE ESRA EE EER ESSERE ig 13 3 1 15 273A 92 Electrochemical Impedance Interface Option EE EE e eee ee 14 A Sirolo oil dee eae ee ech eee be DE DE EE oe TERE DE OE DRA DE ee Se 14 341 14 Polarity Convention ESE SE RE 52555052 5S LEE ERE Ree ER EE REDE ER EP DEE EEO 14 3 1 18x Metric HardWare ee AT ESE SE SEER SE SE SERE GESE SEER GEE ES DEE RE ESE EE BEER EER ie 14 3 2 Internal OrganiZalion DRR RE oe hese hehehe EE hee eee EE RE BAG EE RE REDE PERSE Ee ED 15 3 2 1 Introduction ee ERROR EE EER ER EE SEER SEER EER EOE EE EE EERE EERE DEES PERE ER 15 32 2 BUS commen WE MS OE DEER DEES DEDEDE SE REDE ODS EERS BEES BESEER RE DE EEE 15 3 2 3 Applied Potentials and Currents LL 15 3 24 Analog Cireuits spore EER EER EER DE Dee EE EE DEE EERDER RR EE RE REDE EE RR EER n ie 15 3 2 5 1Cell SwWitch and Relay 2E SEER EER bebe Sees Phebe eee EE REEDE TERE EE EE TREES EEE SO 16 3 2 6 IR COMPCNSALION
33. LABLE Positive Feedback IR Compensation In the Positive Feedback technique an analog positive feedback loop is established from the output of the current measurement circuit to the Control Amplifier Input The user sets the loop gain to exactly the value required to compensate for R The principal advantage of Positive Feedback is that the correction is continuous As a result correction remains effective even at the fastest scans possible with the Model 273A While the technique is the only one possible for rapid scans scans of 100 mV s or faster there are several significant disadvantages 1 Adjusting the feedback is a tedious and subjective process 2 The feedback reduces the stability of the potentiostat and can lead to severe ringing or oscillation 3 Because of the effect on system stability it is generally not possible to achieve 100 compensation Instead the user normally has to be satisfied with a correction in the range of 75 to 90 4 The feedback assumes that the uncompensated resistance is constant Should it vary the applied correction will be incorrect R is frequently not stable it can change with the applied potential time and changes in cell geometry etc Before the Positive Feedback Mode can be activated it is necessary to set and enter the correct value for R the value to be compensated If the entered value is too low R will not be adequately compensated If it is too high the system will be uns
34. Model 273A Potentiostat Galvanostat User s Manual 221266E 0202 Advanced Measurement Technology Inc a k a Princeton Applied Research a subsidiary of AMETEK Inc WARRANTY Princeton Applied Research warrants each instrument of its own manufacture to be free of defects in material and workmanship Obligations under this Warranty shall be limited to replacing repairing or giving credit for the purchase price at our option of any instrument returned shipment prepaid to our Service Department for that purpose within ONE year of delivery to the original purchaser provided prior authorization for such return has been given by an authorized representative of Princeton Applied Research This Warranty shall not apply to any instrument which our inspection shall disclose to our satisfaction to have become defective or unworkable due to abuse mishandling misuse accident alteration negligence improper installation or other causes beyond our control This Warranty shall not apply to any instrument or component not manufactured by Princeton Applied Research When products manufactured by others are included in Princeton Applied Research equipment the original manufacturer s warranty is extended to Princeton Applied Research customers Princeton Applied Research reserves the right to make changes in design at any time without incurring any obligation to install same on units previously purchased THERE ARE NO WARRANTIES THAT EXTEND BEY
35. OMETER MONITOR connector with an oscilloscope with the goal of optimizing the Current Interrupt Parameters as established by Functions 13 17 18 and 19 The selection of the extrapolation points and the Correction setting determine the accuracy of the applied correction Bear in mind that the waveform width interval between disconnect and reconnect is 190 us The thirty two samples spaced at 5 us intervals are located equally spaced in the first 160 us of the waveform Note that the waveform depicted in Fig 7 is idealized actually encountered waveforms may not be so easy to analyze 5 2 12 E Monitor The potential of the working electrode with respect to the reference electrode is continuously provided at this connector This same signal is provided to the Recorder X Drive signal line at the rear panel RECORDER INTERFACE connector A meaningful E MONITOR output is provided as long as there is a reference electrode If there is no reference electrode such as would normally be the case in Galvanostatic operation the E MONITOR output is undefined In Potentiostatic operation if IR COMPENSATION is on either technique the compensation corrects the E MONITOR output level for the IR drop Note This is not the case for the rear panel ELECTROMETER MONITOR output which is not compensated The E MONITOR signal is analog and quite clean free of the steps spikes and similar interference common to digitally produced signals The output impeda
36. OND THE DESCRIPTION ON THE FACE HEREOF THIS WARRANTY IS IN LIEU OF AND EXCLUDES ANY AND ALL OTHER WARRANTIES OR REPRESENTATIONS EXPRESSED IMPLIED OR STATUTORY INCLUDING MERCHANTABILITY AND FITNESS AS WELL AS ANY AND ALL OTHER OBLIGATIONS OR LIABILITIES OF PRINCETON APPLIED RESEARCH INCLUDING BUT NOT LIMITED TO SPECIAL OR CONSEQUENTIAL DAMAGES NO PERSON FIRM OR CORPORATION IS AUTHORIZED TO ASSUME FOR PRINCETON APPLIED RESEARCH ANY ADDITIONAL OBLIGATION OR LIABILITY NOT EXPRESSLY PROVIDED FOR HEREIN EXCEPT IN WRITING DULY EXECUTED BY AN OFFICER OF PRINCETON APPLIED RESEARCH SHOULD YOUR EQUIPMENT REQUIRE SERVICE A Contact the Customer Service Department 865 482 4411 or your local representative to discuss the problem In many cases it will be possible to expedite servicing by localizing the problem B If it is necessary to send any equipment back for service we need the following information 1 Model number and serial number 5 Your telephone number and extension 2 Your name instrument user 6 Symptoms in detail including control settings 3 Your address 7 Your purchase order number for repair charges does not apply to repairs in warranty 4 Address to which the instrument should be returned 8 Shipping instructions if you wish to authorize shipment by any method other than normal surface transportation C U S CUSTOMERS Ship the equipment being returned to Advanced Measurement Technology Inc PHONE 865
37. RACTERISTICS 3 1 Specifications The following specifications apply at the nominal line voltage 10 and at a temperature of 25 C 77 F unless otherwise stated 3 1 1 Power Amplifier gre OD Compliance Voltage gt 100 V Maximum Output Current gt 1 0 A Slew Rate 10 V us high speed Bandwidth Open Loop Unity Gain gt 2 5 MHz Voltage Temperature Stability lt 50 uV C 3 1 2 Differential Electrometer 1 2 3 6 7 Input Impedance gt 10 Q in parallel with lt 50 pF Input Bias Current lt 20 pA at 25 C Maximum Input Voltage Differential 10 V Reference Input 11 V Common Mode Rejection gt 80 dB from dc to 1 kHz gt 40 dB at 100 kHz Bandwidth Small Signal gt 4 MHz Full Signal gt 400 kHz Offset Voltage lt 10 uv Offset Temperature Stability lt 10 uV C 3 1 3 Current Measurement 1 2 Ranges 8 decades 1 A to 100 nA Accuracy dc at Monitor 10 yA to 1 A Better than 0 2 of range 100 nA and 1 pA Ranges Better than 0 5 of range 5 nA max 1 nA typical Frequency Response small signal 1 mA Range 3 dB at gt 1 MHz 1 kQ source impedance 10 yA Range 3 dB at gt 75 kHz 100 kQ source impedance 3 1 4 Potential Current Control 1 Digital Analog Converters DAC s Bias DAC Resolution 14 bits Range 8 V potentiostat 200 of full scale current galvanostat Modulation DAC Resolution 14 bits Range Poten 2 V 0 2 V and 0 02
38. RR bo eS BAON ON eo OE BE PE ES Pe ET EERS EES DEE ee ee ee 5 211 Introduction strie west EE OE SN NAE ea ee pe eae Dad PR WE EERE EE EE SERGE Phe eee ee SANA 5 2 2 Safety Mecha Minsa DORRE EE SEER ER ER EES DERE IERE ER EE SERE ER EE SEER ER ER NG 5 2 3 Power Voltage Selection and Line Fuses LL 5 lee RE NE AE OO OE AA 7 2 5 Defects and Abnormal Stresses ii EE EE EE EE tenet ees 8 2 6 MOMO can sma ane DE ee aa AS BEL EE SEE EER EE TREE ER EE ER ER EE EE 8 2 7 This Apparatus as a Source of Radio Frequency Interference EE a 8 2 8 Eransient SEnsitivily s EER Pe RP pew aes ESE SEE EER BEER EES DE DE EES EE SEER SA NDN 9 9 GHARAGTERISTICS A NG pi ED ED EE DR EE ee E 11 1 Specifications DR RS AE a BEE EE DERE EE eee eS eh ER ER EDE EER ER ER ER ER ER EER ED A 11 3151 Power Amplifier oe DEERE ER EE SES KALI EER SE SEE bE Se hehe EERE EERE EERS BEDE baha 11 3 1 2 Differential Ele trometef lt 14 14 iL EES E nora EE RE ESRA EER EE SEER SEER SEED ER DE 11 31 3 Current Measuremient mang SEE ERROR SR EER SEER EE EE RR REDE EE RE REDE EE RR SS Se DR ES 11 3 1 4 Potentia Gurrent Control EE 14 n ences et SES REL be RE ESRA EER ESRA EER EE SEED EED ES 11 31 9 IREompensatlois casaca orar RE RE EE RE REDE EE RE REDE EE RO SS De Nha 12 AS SR EES ERROR SERE GESE SR AE SE SE SEE PERE ESRA ESE EE SR EE SR EE SEED ER AA 12 31 7 Computer Ihitefidees AE EARLIER LAG SE REDE Dobe EE RE REDE EE RR DE DR PE ES 12 COVO po aed an DRR
39. a second time continues the measurement sequence ADVANCE This key s function differs according to whether a scan sequence is in progress when it is pressed If pressed during a scan it causes the sequence to immediately advance to the next step For example if pressed during the DELAY 1 interval the sequence would immediately advance to SCAN 1 Similarly in half cycle or single cycle scanning if the next step would advance the sequence to the end of the scan the scan would halt If pressed at any other time the message NOT SCANNING is displayed STOP This key stops a scan sequence immediately establishing the end of scan condition and E I 1 on the Scan Status Display lights The applicable Override see Section 5 2 4 determines whether the cell will be ON or OFF CYCLE CONTROL The Cycle Control key allows selection of three different cycle modes HALF CYCLE SINGLE CYCLE and CONTINUOUS A separate indicator is provided for each and one of the three will always be lighted Selection is accomplished with the associated key Each time the key is pressed the selection increments the sequence being HALF CYCLE to SINGLE CYCLE to CONTINUOUS and from there back to HALF CYCLE A brief description of each follows a HALF CYCLE This is the simplest cycle involving only two potential current settings A half cycle sequence proceeds as follows i DELAY 1 at E 1 Model 273A Potentiostat Galvanostat User s Manual ii SCAN1
40. a the command set EXT command The Model 273A Remote Programming Command Handbook describes the computer command set 3 2 4 Analog Circuits The analog section of the Model 273A comprises three operational amplifiers They are 1 the Control Amplifier 2 the Electrometer and 3 the Buffer Amplifier that drives the VE MONITOR connector Note that this potentiostat does NOT incorporate a grounded potential working electrode the working electrode can be off ground by as much as 2 V The 2 V occurs because of the potential drop across the current sensing resistor Buffer Amplifier Measurement Circuit Referring to Fig 3 note the Current Range Relays in the box to the right of the Buffer Amplifier that drives the I E MONITOR connector These computer controlled relays select any one of the Chapter 3 Characteristics 15 16 eight Current Range Resistors Values from 10 to 10MQ can be selected with the result that a full scale current 1 A to 100 nA will cause a drop of 1 V Since currents as high as two times full scale are permitted on all but the 1 A range drops as high as 2 V can occur The circuit is configured such that the Buffer Amplifier makes a four terminal measurement of the voltage drop across the Current Measurement Resistor thereby assuring that the current measurement is independent of cable and switch contact resistance in the switch and in the connecting cell interface Differential Electrometer The Different
41. able resistance capacitance and inductance The Model 273A uses an external differential electrometer Not only does this approach further assure freedom from cell cable effects but it allows the use of two reference electrodes to control the potential across an interface such as a membrane In addition the electrometer can be configured to provide a remote sensing contact to the working electrode and so eliminate any potential error resulting from high current in the contact resistance 1 2 About this Manual The Model 273A Potentiostat Galvanostat can be operated either directly with its front panel controls or remotely from a personal computer or workstation This Instruction Manual provides details of the physical and electrical characteristics of the Model 273A and describes how to operate it as a stand alone instrument controlled from its front panel Instructions for operating the unit remotely via either the RS 232C or GPIB IEEE 488 interface port are given in the separately bound Model 273A Remote Programming Command Handbook In addition to the command descriptions the Command Handbook gives detailed explanations of GPIB IEEE 488 and RS 232C communications including rear panel switch settings communications protocols and some useful communications routines Also included in the Command Handbook is an application note on waveform programming one of the most useful functions of the Model 273A This Instruction Manual is org
42. alvanostat mode the range is 1 uX s to X s where X is the selected current range STEP can also be selected in which case the applied Potential Current simply steps as quickly as possible from one level to the other STEP is useful for applying pulse waveforms Example a To seta Scan 1 rate of 1 mV s key SCAN 1 1 ENTER b To key a Scan 2 rate of 50 A s with a Current Range setting of 100 UA key SCAN 2 5 ENTER Since the desired scan rate units are half the Current Range the keyed value is simply 5 c To substitute a potential step for Scan 1 key SCAN 1 STEP ENTER EXP This key is used to set parameters using engineering notation For example to set Delay 1 to 1000 seconds one could key DELAY 1 1 0 0 0 ENTER or DELAY 1 1 EXP 3 ENTER or DELAY 1 1 0 EXP 2 ENTER and so forth EXP can be regarded as belonging to the numeric keypad subset FUNCTION This key accesses the Setup Functions Each function initiates an action not available via the other keys A function is accessed by keying FUNCTION followed by the number corresponding to the desired function A number of special functions are provided Although memory space for 90 functions has been provided range is 10 to 99 the number actually available is much smaller The first available function is FUNCTION 10 the next is FUNCTION 11 and so forth up to the highest one defined A brief description of
43. an external computer via the GPIB or RS 232C port Note This output is intended for use with Princeton Applied Research electrochemical impedance systems 12 AC INPUT used only in units equipped with the 273A 92 Electrochemical Impedance Interface option This connector accepts a sine wave input from an external oscillator such as that supplied by a Princeton Applied Research lock in amplifier The nominal frequency range is 50 uHz to 100 kHz although this is dependent on loading Input voltage must be no greater than 5 volts rms This signal can be used to modulate the signal sent by the Model 273A to the cell and can be attenuated as desired It is controlled by commands from an external computer via the GPIB or RS 232C port 3 1 15 273A 92 Electrochemical Impedance Interface Option The 273A 92 Electrochemical Impedance Interface option previously called the AC Interface option is intended primarily for use with Princeton Applied Research electrochemical impedance systems but can also be used for ac voltammetry applications This option is designed to allow superposition of an externally generated ac excitation signal on the dc signal generated by the Model 273A The Model 273A Remote Programming Command Handbook describes the computer commands used with the Model 273A 92 option Section 3 2 10 of this chapter describes how it works 3 1 16 Accessories 1 MODEL 407A INTERFACE This accessory allows the Model 273A to be used in conjun
44. anel E MONITOR signal and a contact closure for the Pen Up Down function Two different recorder cables are available C174 connects directly from the RECORDER INTERFACE connector to the interface connector on either the RE0150 or RE0151 recorder With this cable installed the OUTPUT signal drives the Y axis the E MONITOR signal drives the X axis and the pen closure requirements are provided for For operation with other recorders or with an RE0150 or REO151 recorder in applications where the normal X and Y axis drive signals are to be reversed corrosion cable C178 is recommended One end of this cable has a connector that mates with the Model 273A s RECORDER INTERFACE connector At the other end are two pairs of banana plugs and two leads terminated in spade lugs that provide the pen drop contact closure One pair of banana plugs provides the OUTPUT signal the other the E MONITOR signal Either can be connected to either the X axis or Y axis inputs of the recorder Chapter 5 Operating Instructions 49 One of the two terminals of each banana plug pair has a small tab and is labeled ground This ground terminal connects to the recorder terminal X or Y as appropriate marked Houston or LO Hewlett Packard The recorder terminal labeled GROUND on Houston recorders is not used in operation with the Model 273A A relay contact closure inside the Model 273A is brought out to the pen drop leads These leads float with respect to
45. anized into five chapters and three appendices Chapter 1 provides a general description of the Model 273A Be sure you understand the information in Section 1 4 about the polarity convention used in this instrument The 100 V output and high current capability of the Model 273A make it potentially lethal if not used with care and respect Chapter 2 describes recommended safety precautions for operating it Chapter 2 also explains how to set the instrument for operation with different input power voltages replace the power line fuse and determine whether power is applied to the counter electrode connector Chapter 3 describes the physical and electrical characteristics of the instrument It includes a description of the electrical circuitry and internal organization of the instrument and the functions of the front and rear panel connectors Pinouts of the connectors are given in Appendix A and schematic diagrams and component layouts are shown in Appendix C After you inspect the Model 273A for shipping damage but before you begin to use it run the initial performance checks given in Chapter 4 to ensure that the instrument operates correctly Then using the operating instructions given in Chapter 5 you may begin operation of your unit The Model 273A may be mounted in a standard 19 in 475 cm rack assembly Appendix B provides mounting instructions 1 3 Controlling the Model 273A Front Panel Controls The front panel is configured for
46. anual Safety Instructions and Symbols This manual contains up to three levels of safety instructions that must be observed in order to avoid personal injury and or damage to equipment or other property These are DANGER Indicates a hazard that could result in death or serious bodily harm if the safety instruction is not observed WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not observed CAUTION Indicates a hazard that could result in property damage if the safety instruction is not observed Please read all safety instructions carefully and make sure you understand them fully before attempting to use this product Cleaning Instructions WARNING Using this instrument in a manner not specified by the manufacturer may impair the protection provided by the instrument To clean the instrument exterior e Unplug the instrument from all voltage sources e Remove loose dust on the outside of the instrument with a lint free cloth e Remove remaining dirt with a lint free cloth dampened in a general purpose detergent and water solution Do not use abrasive cleaners CAUTION To prevent moisture inside of the instrument during external cleaning use only enough liquid to dampen the cloth or applicator e Allow the instrument to dry before reconnecting the power cord vi Model 273A Potentiostat Galvanostat User s Manual 1 INTRODUCTION 1 1 Overview The Model 273A Potenti
47. apter 5 Operating Instructions 43 44 is optimum for fast measurements As the compensation is increased to the 95 to 100 range increasing ringing appears as the system becomes more unstable This level of compensation is not suitable for fast measurements Any data taken during the ring down will be of doubtful validity Also even a slight increase in compensation from this point or a real decrease in the actual R could cause the potentiostat to oscillate Compensation in the 95 to 100 range is best suited to slow experiments corrosion Since Current Interrupt Compensation is ideal for slow measurements there will normally be relatively few instances where Positive Feedback Compensation in the 95 to 100 range would be used LARGE UNCOMPENSATED RESISTANCE TOO LITTLE IR COMPENSATION SLOW RESPONSE 100 MUCH IR COMPENSATION HIGH AMPLITUDE FAST RESPONSE WITH RINGING CORRECT IR COMPENSATION FAST SMOOTH RESPONSE Fig 6 Monitor Waveforms as a Function of R Compensation Square Wave Applied When you are satisfied with the compensation level turn off the cell and do the Scan Setup appropriate to the intended measurement Unless changed the set compensation level will remain in memory ready to be applied whenever POSITIVE FEEDBACK is activated Current Interrupt IR Compensation In this technique the current is periodically interrupted and a correction function developed that is based on the time versus potential c
48. ble modes HIGH SPEED or HIGH STABILITY will always be in effect and the corresponding indicator will glow The key is used to alternate between the two modes Stability Speed selection is entirely independent of whether the instrument is operated as a potentiostat or galvanostat The HIGH SPEED mode gives the fastest response see specifications in Potentiostat or Galvanostat operation but without guaranteed stability Under the proper conditions with certain cells ringing almost always occurs and oscillations may occur Cells having large capacitance and low resistance are most likely to prove troublesome The HIGH STABILITY mode provides extreme stability at somewhat reduced speed see specifications In this mode stable operation is assured with virtually any cell However the possibility always exists that with an unfamiliar cell configuration or under extremely unusual operating conditions stability problems might occur If oscillation does occur in the HIGH STABILITY mode it usually results from a high resistance reference electrode Evena well designed low impedance reference electrode can develop a high resistance if salts precipitate in the junction OPERATING MODE There are three basic operating modes each with its own key and indicator One of the three modes will be in effect at all times as indicated by the associated indicator To transfer from the mode in effect to either of the other two modes simply press the target mod
49. briefly discussed in the following paragraphs Chapter 5 Operating Instructions 51 52 1 Fig 9 Electrometer REFERENCE ELECTRODE JACK The reference electrode plugs directly into this white jack Several suitable electrodes are available from Princeton Applied Research CELL SWITCH This switch has two positions DUMMY and EXT Normal operation occurs in the EXT position In the DUMMY position a 100 kQ 1 resistor inside the Electrometer Housing is substituted for the cell The feature is useful for determining that the Model 273A is functioning correctly Note that this is a locking type toggle switch To change the setting it is necessary to grasp the bat and pull it outwards a millimeter or two to release the catch Warning This switch provides no protection against the possibility of dangerous potentials being present at the cell cable leads These leads can be handled safely only when the front panel cell enable switch is in the off position A SENSE and WORKING ELECTRODE JACKS These two jacks are used together to give the operator control of the sense function The upper gray jack is internally connected directly to the reference input of the Electrometer Amplifier The lower green jack is connected internally to the adjacent Working Electrode lead which ends in a clip having a green insulating boot In operation the working electrode of the cell must be returned to the reference input of the Electrometer
50. ction with the Model 303A Static Mercury Drop Electrode This adapter requires two cables to make the necessary connections One cable connects to the Model 273A AUXILIARY INTERFACE connector and the other to the Model 303A INPUT connector The Model 407A requires 24 V at 1 A A suitable power supply is included with it 2 MODELS RE0150 and REO151 RECORDERS These recorders are well suited to use with the Model 273A and a custom cable is available to simplify the necessary interconnections Both recorders use 11 x 17 inch paper The principal difference between them is that the RE0151 incorporates a time base 3 In addition a variety of cells electrodes and other items are available as described in the Princeton Applied Research Electrochemical Accessories Catalog 3 1 17 Polarity Convention The Model 273A follows the American polarity convention and the display indications are consistent with that convention Positive current is cathodic that is a current is defined as positive if reduction is taking place Negative current is anodic that is a current is defined as negative if oxidation is taking place A full description of the polarity convention used is given in 1 1 4 3 1 18 Metric Hardware Equipment manufactured by Princeton Applied Research uses American Standard and metric fasteners and related hardware For this reason an electronic technician servicing or aligning the apparatus should make a special effort to keep track of
51. ctrometer Monitor Connector After interrupt thirty two samples are taken at 5 us intervals Two of these are selected Functions 18 and 19 and extrapolated back to the moment of interrupt The goal is to select two points that will provide a projection that exactly intersects the lower end of the iR drop If the intersection occurs at a higher point the correction factor will be too small If it occurs at a lower point as is the case for the example depicted in the figure the correction factor will be too large Fortunately Function 17 by allowing user control of the percentage of correction eases the point selection task For example if the extrapolated line were to intersect exactly halfway down the drop the correction factor would be 50 of the required value The resulting correction factor could be easily adjusted to its proper value by using Function 17 to set the Correction to 200 Similarly if the intersection occurred below the drop as in the depicted example Function 17 would be used to set a Correction of less than 100 90 would be about right for the example Once the parameters are set via the required functions and Current Interrupt IR Compensation established no other operator intervention is required during the measurement Current Interrupt IR Compensation has several advantages with respect to Positive Feedback IR Compensation 1 This technique corrects for essentially the entire potential error caused by th
52. d remain lighted for 10 s the programmed delay interval The displayed potential and current will remain constant Chapter 3 Characteristics 23 24 17 18 19 g The SCAN 1 indicator scan status display will light and remain lighted for the 50 s it takes to complete the first leg of the scan at 20 mV s As the scan advances the display will indicate the increasing potential and current The E I 2 indicator scan status display will flash once indicating that the scan has reached 1 V the programmed vertex potential The DELAY 2 indicator scan status display will light and remain lighted for 10 s the programmed delay interval The displayed potential 1 V and current 10 HA will remain constant The SCAN 2 indicator scan status display will light and remain lighted for the 50 s it takes to complete the second leg of the scan at 20 mV s As the scan advances the display will indicate the decreasing potential and current The E I 3 indicator will light and remain lighted indicating that the scan is complete Set the CELL ENABLE switch to OFF Press the CELL ON OFF key establishing the Cell OFF state The associated indicator light should extinguish Set the Model 273A POWER ON OFF switch to OFF This completes the initial checks If the indicated behavior was observed the user can be reasonably confident that all circuits up to and including the electrometer are functioning normally Model 273A Potenti
53. de connection remains intact and the final E I continues to be applied Note that in the CONTINUOUS control mode the experiment doesn t end until the STOP key is pressed At the point the cell status is that determined by this override Model 273A Potentiostat Galvanostat User s Manual OVERRIDE 14 LINE SYNC This override determines whether data acquisition will be synchro nized with the power line frequency If YES samples are taken every 16 6 ms 60 hz power or every 20 ms 50 Hz power If NO samples are taken at the rate determined by the internal time base The default state of this override is NO Note that if the Override 14 status is changed while a scan is in progress the scan will stop It can be restarted only by pressing the START key 7 1 YES and 2 NO As previously explained these are dual function keys In specifying an Override they act as YES NO designators In keying a parameter value they simply specify the numbers 1 and 2 In this capacity these keys are part of the numeric keypad 8 NUMERIC KEYPAD This subset of the Scan Setup keys consists of 1 YES 2 No 3 4 5 6 7 8 9 0 LL and EXP These keys are used to actually key the parameter values As each key is pressed the corresponding character appears in the display As explained in the previous two paragraphs 1 YES and 2 NO have alternate functions EXP precedes an exponent to the base 10 and is used to exp
54. delay will last as long as it has to measuring the potential all the time until the drift rate drops below the specified figure Delay values from 0 001 mV s to 10 mV s can be set Should the drift change polarity premature termination could occur Drift rate delays should always be done with the Cell OFF It is the user s responsibility to establish the required OFF state with the Scan Setup CELL OFF key Note that the cell potential must be monitored for some time to acquire the data needed for the driftrate calculation Very low settings require long measurement times up to a maximum of 1000 s Once the delay interval ends the scan begins and the potential current if not applied during the delay is applied The Cell is ON during a scan whatever its status during the preceding delay Examples a Toseta Cell ON Delay 1 of 15 s key DELAY 1 5 SEC ENTER b To set a Cell OFF Delay 2 of 0 1 s key DELAY 2 0 1 SEC CELL OFF ENTER c To seta Delay 1 of 02 mV sec key DELAY 1 0 2 mV SEC ENTER Chapter 5 Operating Instructions 29 30 3 d To bypass Delay 1 in the scan sequence key DELAY1 PASS ENTER SCAN 1 and SCAN 2 These keys set the scan rate for the two scan legs SCAN 1 applies to the scan from E I 1 to E I 2 SCAN 2 applies to the scan from F I 2 to E I 3 Scan rates from 1 uV s to 1 V s can be specified in the Potentiostat mode keyed units are mV s In the G
55. dump before the command is completed LISTEN This indicator lights when the Model 273A senses the first character of a command It remains lighted until the terminator is sensed The LISTEN indicator does NOT signal that the host computer has transmitted a LISTEN message Rather it indicates that the Model 273A is expecting more input before the current command is fully defined REMOTE This indicator lights when the Model 273A is under remote control via the GPIB interface that is REN is asserted and the Model 273A s LISTEN address has been applied As long as the REMOTE indicator is lighted the Model 273A s front panel is locked out Return from remote to local operation can be accomplished simply by pressing the adjacent LOCAL key only effective if the LOCAL LOCKOUT message hasn t been applied Other ways of returning to local include applying the GO TO LOCAL message deasserting REN or cycling the power Note LOCAL LOCKOUT and GO TO LOCAL are GPIB messages defined by IEEE 488 SRQ This indicator lights when sro is asserted that is when the Model 273A has initiated a service request The use of SRQ and serial polling to control GPIB communications is discussed in Subsection B 4 of Appendix B of the Model 273A Remote Programming Command Handbook It remains lighted until the controlling computer completes a serial poll of the Model 273A or the power is cycled ERROR This indicator lights if there was an error in the most recently e
56. e uncompensated resistance Chapter 5 Operating Instructions 45 2 This technique corrects for any changes in the uncompensated resistance as the scan progresses 3 No adjustment is required on the part of the user The only action required is the simple press of a button to enable the correction The default values of Functions 13 17 18 and 19 will give good results in many applications Disadvantages of the technique include 1 The correction occurs at finite times Thus the technique is not suitable for scan rates greater than 500 mV s and may in fact not work properly at scan rates greater than 100 mV s 2 If the correction isn t updated frequently enough the applied correction can be in error 3 In some cases this technique can cause the entire system to oscillate The procedure for establishing Current Interrupt IR Compensation is very simple Simply press the CURRENT INTERRUPT key The associated indicator will light and the iR drop will be automatically compensated in subsequent measurements To turn the technique OFF simply press the CURRENT INTERRUPT key again the indicator light will extinguish Note If the cell is turned OFF while current interrupt is selected the current interrupt routine is skipped and no correction occurs When the cell is turned back on the current interrupt routine resumes Once Current Interrupt Compensation is running the user may wish to monitor the waveform at the rear panel ELECTR
57. e Ee EE Ge Ge GE Ge EE RE RE Re Re Rg eg gee 48 5 3 1 Cell INTCM ACE usura EA EP er RR gr ANAN 49 5 8 2 Recorder Interface AE ER A N NA Ge EDE ee MEd 49 5 3 3 AuxiliarysInterface pada ee a a a ER SS eN Mg i 50 5 34 Powef ArmpMODILOF tt EE EE a er EE RS STD Ee Re Re ge Me 50 5 3 0r AUX A D INPUT astia AA OE Ed 50 5 3 6 ElectrometeriMOnitor manage ere E Re EE a aaa 50 50 3 AGL OUUU RE ER AA a a Ed 50 5 3 8 ACE OUDUE EER SR EE SR IRR ARTISTA ER STD Re ie Re REG ee 50 5 3 9 Multiplexed Output suster EE EET ES aaa er RR gr ANAN 51 5 3 10 Sel EA OE RA ER ER EE ET 51 5 3 11 273A 92 Electrochemical Impedance Interface Option 51 5 38 12 to KO aie EER ER EE EI 51 5 3 13 IEEE 488 GPIB Interface ss e ee ee eee 51 5 4 Differential ElectroMeter is SE Es ee tee 51 5 5 Model 273A Standard Environmental Conditions 53 5 5 1 Operating Conditions Ee eg O ES RR ea aed ER RES er Ee eer gel ge 53 5 5 2 Non Operating Conditions LL 54 5 5 3 International Standards 54 APPENDIXA PINOUTS magana a AA etna 55 Ada Cell Interface 36 PINS sesse se Ka Ao 55 A 2 Recorder Interface mating connector DP15P 0 00 eee ee 55 A 3 Auxiliary Interface mating connector DBIS EE eee 56 Ad IEEE 488 GPIB Interface se ee ed tees 57 Ab RS 232G INteridoe nawa anna ana 58 APPENDIX B RACK MOUNTING Ee EE EG ee GR ee Ge ete eens 59 INDEX pfe EE EE ta 61 iv Model 273A Potentiostat Galvanostat User s M
58. e key a POTENTIOSTAT In this mode the 273A controls the potential of the working electrode with respect to the reference electrode The potential at the counter electrode is driven to the potential required consistent with the 100 V compliance of the Control Amplifier to establish the desired working electrode potential b GALVANOSTAT In this mode the 273A controls the cell current at the specified faction of the selected Current Range up to the maximum of two times the Current Range one times the range if 1 A is selected The counter electrode is driven to the potential required consistent with the 100 V compliance of the Control Amplifier to establish the desired cell current No reference electrode is required although one can be used to monitor the potential if desired c MEASURE ONLY The open circuit cell potential is continuously monitored and displayed in this mode Neither the potential nor the current is controlled The cell is OFF even if Cell ON has been previously selected with the Cell key If an attempt is made to turn the Cell ON while in the Measure Only mode the message CAN T TURN CELL ON IN MEASURE ONLY is displayed See 5 2 9 for a discussion of the effect of a voltage applied to the External Input on the signals routed to the electrochemical cell 5 2 8 CELL Group There are two keys and one indicator in this group All three are associated with the internal switches that provide the connection to the count
59. e used to ground a piece of peripheral apparatus such as an electrostatic shield Usually this lead isn t used TAKE CARE THAT THE ELECTROMETER LEAD CLIPS NOT SHORT TOGETHER Because the ground lead is often unused it tends to be overlooked making the possibility of an accidental short involving this lead more of a problem than for the other two 5 5 Model 273A Standard Environmental Conditions 5 5 1 Operating Conditions This equipment shall meet all specified performance criteria when subjected to any natural combination of stress A Input Voltages 1 100 120 volts AC 50 to 60 Hz 2 200 240 volts AC at 50 to 60 Hz B Ambient Temperature From 10 C to 40 C 1 The instrument shall operate from 10 C to 40 C but may not meet some temperature related specifications 2 The instrument shall operate from 20 C to 30 C and meet all its specifications over this range Chapter 5 Operating Instructions 53 54 C Relative Humidity from 5 to 85 non condensing D Altitude from 500 to 9000 feet relative to sea level 5 5 2 Non Operating Conditions This equipment shall exhibit no significant deterioration of performance after exposure to any natural combination of stress in 2 1 through 2 3 in a non operating condition A Ambient Temperature range from 6 C to 70 C B Relative Humidity greater than 95 with modest local condensation or frost formation Instrument must be allowed to remain at operating conditions f
60. each follows FUNCTION 10 REINITALIZE SYSTEM This function allows all of the parameter selections to be cleared and the default values to be restored When it is accessed the message REINIT SYSTEM is displayed At that point the operator presses the YES key or the NO key 1 or O or the keypad as appropriate followed by ENTER If YES all parameter selections are cleared Model 273A Potentiostat Galvanostat User s Manual and default values restored Note that the effect is NOT the same as that which occurs when the power is cycled When the Model 273A powers down all parameter values and selections are retained When it is powered up most of the values in effect at the time that power shutdown occurred are restored The exceptions are the errors and SRQ which are cleared by cycling the power See Command Handbook for more information FUNCTION 11 PRINT OUT INSTALLED OPTION This function allows the user to determine at a glance whether an option is installed in the unit When accessed the number corresponding to the installed option is displayed If a unit is equipped with the 273A 92 option the number 92 would be displayed FUNCTION 12 ENTER LOG REFERENCE This function allows the user to specify the Current Range for which a full scale current will yield 0 V out in the LOG mode When accessed the message ENTER LOG REFERENCE is displayed At that point the user keys a number from 0 1 A range to 7 100 nA range The numbe
61. een 150 mV and 1 9 V If the current level is less than 15 nA the 100 nA range will be selected If it is more than 1A the 1 A range will be selected This process occurs after each point is acquired with the constraint that it can only change one range at a time Data can be lost if the data amplitude is changing faster than it can be tracked by the auto ranging function Auto ranging is restricted to CONTROL E operation Should the user attempt to select Auto Ranging in CONTROL operation an error message will be generated Automatic current ranging is additionally affected by the LOW PASS filter if selected If LOW PASS is selected there is a 150 ms dead time after each range change No further current ranging can occur during this dead time which is inserted to allow the input to settle before making a new ranging decision Note however that an overload even if it occurs during a dead time interval will always force a range shift to the next higher current range and that the overload detection circuit is not affected by the presence of a filter 5 2 14 OUTPUT Group There are three keys three indicators and a BNC connector in this group A voltage dependent on the cell current or transferred charge is available at the OUTPUT connector identically the rear panel Recorder Y Axis Output The other items in the group either set or indicate the nature of the dependency 1 OUTPUT An analog of the cell current is available at this
62. er electrode red clip lead The CELL ENABLE pushbutton has two positions in ON and out OFF CELL ENABLE is a hard wired fail safe Model 273A Potentiostat Galvanostat User s Manual switch Whenever it is in the OFF position there is no possible way including commands from an external computer for voltage to be applied to the counter electrode This switch is provided to assure operator safety when working on the cell Warning When working with the cell including making and breaking connections the CELL ENABLE switch must be in the off position The 100 V output and high current capability of the 273A make it a dangerous device one capable of causing severe injury or even death The connections should be handled only The upper Cell key provides the normal Cell ON OFF control during operation Unlike the CELL ENABLE switch this key is subject to software override For example the ON state must be selected before starting a scan However a scan may contain delay intervals to be carried out in the Cell OFF state If this is the case the cell is turned off automatically at the appropriate points in the measurement sequence The Cell indicator light gives the cell status at all times This red indicator has three states OFF HALF BRIGHT and FULL BRIGHT The significance of each state is OFF Both the CELL key and the CELL ENABLE switch are OFF or the CELL key is OFF and the CELL ENABLE switch is ON HALF BRIGHT CELL key is ON
63. ere the range is restricted to 1 V The input impedance is 100 kQ In potentiostatic operation all of the control potentials add algebraically For example if the voltage applied to the EXTERNAL INPUT is 0 5 V at a time when a programmed potential of 0 5 V is applied the net potential seen by the Model 273A will be 1 0 V and the working electrode would be controlled at 1 0 V with respect to the reference electrode A positive applied potential will make the current tend to be more anodic A negative applied potential will make the current tend to be more cathodic Chapter 5 Operating Instructions 39 In galvanostatic operation making the applied current more positive by any means except applying a potential to the EXTERNAL INPUT connector will tend to make the current more cathodic making the applied current more negative will tend to make the current more anodic This sense is reversed at the external input connector There making the input more positive will make the cell current more anodic Making the input more negative will make the cell current more cathodic Bear in mind that the EXTERNAL INPUT is a high impedance potential input in both potentiostatic and galvanostatic operation In potentiostatic operation a volt at the External Input results in a volt at the working electrode other control sources zero In galvanostatic operation a volt at the External Input results in full scale cell current other control sources zero
64. erest 11 STEP This key is used to substitute a step between two levels instead of a scan The applied potential current will step as quickly as possible between the two levels Another operation cannot be initiated for 4 ms The step feature allows the Model 273A to perform double potential step chronoamperometry in which the applied potential starts at E I 1 remains there long enough to let the sample come to equilibrium with the solution steps to E I 2 for DELAY 2 seconds and then steps to E I 3 which continues to be applied Example To substitute a step for SCAN 1 key SCAN 1 STEP ENTER 12 PASS This key allows one or both delays to be dropped from the scan sequence A passed delay is 4 ms Chapter 5 Operating Instructions 33 34 13 14 15 16 Example To drop DELAY 2 from the scan sequence key DELAY 2 PASS ENTER SEC This key is used in conjunction with either of the DELAY keys to specify a delay interval in seconds Example To set a DELAY 1 interval of 100 s key DELAY 1 1 0 0 SEC ENTER mV SEC This key is used in conjunction with either of the DELAY keys to specify a delay interval in drift units Defining the delay in this manner is particularly well suited to experiments where the specimen must be allowed to come to equilibrium before valid measurements can be taken The open cell potential is monitored allowing the drift rate to be measured as it asymptotically appr
65. f this amplifier However only three of these inputs are sources of applied control potential or current that is user controlled sources that are summed together and that directly set the current or potential applied to the cell Those three are 1 BIAS DAC Digital to Analog Converter the output of which is scaled to provide either 8 V in applied E Mode or 2X full scale current in APPLIED mode 2 MOD DAC the output of which also 10 V is scaled to 2 V 20 mV 20 mV in APPLIED E mode operation or 2 x full scale in APPLIED mode operation 3 EXT INPUT The voltage applied to the input causes an equal voltage to be applied to the cell in CONTROL E mode In CONTROL 1 operation 1 V applied to this input causes one full scale of current to be applied to the cell As previously mentioned these sources are summed However the sum must not exceed 10 V in APPLIED E operation or 2 times full scale current up to 1 A maximum in APPLIED operation Each of these three inputs can be disabled without changing the values at the DAC s by means of the associated CMOS switches switches depicted in rectangular boxes The switches for the two DAC s are shown to the right of the Scaling Circuits The switch for the External Input is shown to the right of the Buffer Amplifier Note that the switches for the DAC s cannot be accessed from the front panel or via the command set The External Input switch on the other hand is controllable vi
66. from E I 1 to E I 2 iii Scan STOPS on reaching E I 2 During DELAY 1 the cell can be either ON or OFF as programmed During SCAN 1 the Cell will be ON At the end of the scan the E I 2 indicator will remain lighted The cell will remain ON or OFF according to the state of the applicable Override b SINGLE CYCLE A Single Cycle is more complex and involves all three programmed potential current levels The sequence is i DELAY 1 at E I 1 ii SCAN1 from E I 1 to E I 2 ii DELAY 2 at E I 2 iv SCAN 2 from F I 2 to E I 3 Scan STOPS on reaching E I 3 During DELAY 1 and DELAY 2 the cell can be either ON or OFF as programmed During SCAN 1 and SCAN 2 the Cell will be ON At the end of the scan the E I 3 indicator will remain lighted The cell will remain ON or OFF according to the state of the applicable Override c CONTINUOUS Continuous is the most complex of the three cycles The sequence is as follows i DELAY 1 at E I 1 i SCAN 1 from E I 1 to E I 2 iii DELAY 2 at E I 2 iv SCAN 2 from F I 2 to E I 3 v DELAY 1 at E I 3 vi SCAN 1 from F I 3 to E I 2 vii Steps iii through vi repeat until STOP key is pressed During DELAY 1 and DELAY 2 the cell will be either ON or OFF as programmed During SCAN 1 and SCAN 2 the cell will be ON Automatic cycling of the scan back and forth from E l 2 to E I 3 will continue until halted by pressing the STOP key The cycle returns to E I 1 when STOP is pressed The cell
67. hange that occurs at the moment of interrupt Specifically the cell is disconnected in less than 1 us for 190 us at periodic intervals As fast as the interrupts are they nevertheless do affect the experiment and a small artifact may be noticed in the output for each interrupt At disconnect a drop in the Electrometer potential equal to R occurs Thirty two potential points are then taken at 5 us intervals Two of these points are used to define a projection that is extrapolated back to the instant just after current interruption By comparing the potential at that instant with that before the interruption a correction function is developed that corrects for the uncompensated IR drop in the cell Several functions see Section 5 2 4 are involved in setting the Current Interrupt parameters FUNCTION 13 sets the interval between current interrupts The range is 004 s to 30 s with a default setting of 1 s In doing Curve Acquisition with the 273A controlled from a host computer the interrupt timing is controlled by the computer FUNCTION 17 sets the percentage of correction adjustable from 0 to 200 FUNCTION 18 selects the first of the two extrapolation points The range is 2 to 1997 us The default selection is 10 us on the 1 Aand 100 mA Current Ranges and 75 us on all other Current Ranges FUNCTION 19 selects the time increment used to determine the second point The selection range for the increment is also 2 to 1997 us The defaul
68. ial Electrometer is located in a remote enclosure to minimize lead capacitance This differential electrometer allows accurate potential control independent of lead and contact resistance The inverting input of the electrometer connects to the working electrode top of the current sensing resistor either directly or via the sense lead if the remote sense is enabled by removing the sense jumper and running a separate sense lead to the cell The non inverting input of the electrometer is normally connected to the reference electrode Thus the output of the electrometer is the potential of the reference electrode versus the working electrode that is the parameter to be controlled in CONTROL E operation and measured in the CONTROL operation Control Amplifier Power Amplifier This circuit is basically a 100 V 1 A power operational amplifier The various input signals are applied through resistors not shown and summed together at the input of the Control Amplifier The output of the Control Amplifier is driven to whatever voltage is required to cause the feedback signal to be equal and opposite to the summed input signals The feedback signal is an analog of either the cell potential or current as determined by the E or feedback switches according to the operating mode In the CONTROL E mode the feedback signal is taken from the electrometer In the CONTROL mode it is taken from the current measurement circuit The Control Ampl
69. ifier has computer controlled frequency response shown in the block labeled STABILITY SELECTION In both CONTROL E and CONTROL operation the HIGH STAB mode limits the bandwidth of the Control Amplifier by changing the capacitor in its feedback loop This is done to assure stability on most routinely encountered cells and experimental situations The Control Amplifier is faster without these frequency adjusting components but may oscillate under certain conditions Note that a Power Amp Monitor point is provided at the rear panel To eliminate any shock hazard the amplifier s output voltage is internally divided by ten prior to being brought out to the Monitor point 3 2 5 Cell Switch and Relay Referring to Fig 3 note the Cell Switch and Cell Relay shown in series between the output of the Control Amplifier and the counter electrode connection red clip lead Even though the block diagram shows two switches in series there are actually three of them The first is the manually operated CELL ENABLE Switch provided at the front panel as a fail safe means of rendering the red clip lead harmless The second switch is a high speed solid state device and cell relay capable of connecting and disconnecting the cell in less than one microsecond Although primarily intended to implement Current Interrupt IR Compensation it is also used for connecting and disconnecting the cell to provide glitchless transitions from Cell ON to Cell OFF and vice versa
70. ine Blank b Charge in Coulombs c Log of if LOG is Enabled d Status of the Scan Possibilities include i Delay Time Remaining Delay specified in seconds ii Time Remaining Until Drift Measurement Can be Made Delay specified in mV s Alternatively measured drift rate if measurement has taken place iii Stopped Scan Model 273A Potentiostat Galvanostat User s Manual iv E Applied or Applied according to selected mode Note If the scan proceeds too fast for the bottom line of the display to be updated in real time the message SCANNING will be displayed on the bottom line 5 2 5 INTERFACE Group This area of the panel contains five indicators and a pushbutton They provide useful information when controlling the Model 273A from a remote computer When the instrument is under front panel control all five indicators should be extinguished and the LOCAL key will have no function When controlling from a remote computer via the GPIB or RS 232C port all five indicators and the pushbutton are active although SRQ REMOTE and the pushbutton apply to GPIB communications only A brief description of each follows 1 TALK This indicator lights when the Model 273A has output ready to send to the host computer It goes out when the Model 273A has finished sending this output The TALK indicator does NOT signal that the host computer has transmitted a TALK message Rather it indicates that the Model 273A has more output to
71. ion Card Position as a Function of Line Voltage SELECTOR CARD OPERATING NUMBER EXPOSED VOLTAGE RANGE EE ER IE HEER 90 110V 120 SE RE RD aa Aa 110 L30 V RE EE a ma 210 230 V RR Ga eee 230 260 V Next check the fuse rating For operation from a line voltage in either of the two lower ranges use a slow blow fuse rated at 4A voltage rating 125 V or higher For operation from a line voltage in either of the two higher ranges use a slow blow fuse rated at 2 A voltage rating of 250 V or higher When the proper fuse has been installed slide the plastic door back over the fuse compartment so that the power cord can be reconnected Make sure that only fuses with the required current rating and of the speed type are used for replacement The use of makeshift fuses and the short circuiting of fuse holders are dangerous 2 4 Cell Cable Warning Potentials as high as 100 V capable of delivering currents as high as 1 A may be present at the cell connections To avoid the possibility of dangerous electrical shock always have the cell disabled when working with the cell connections The cell status is determined by the two keys in the cell area of the Model 273A front panel These keys function as follows There are two keys and one indicator in this group All three are associated with the internal relay that provides the connection to the counter electrode at the cell The CELL ENABLE key has two positions in ON and out OFF CELL ENABLE
72. is a hard wired fail safe switch Whenever it is in the OFF position there is no possible way including commands from an external computer for voltage to be applied to the counter electrode This switch is provided to assure operator safety when working on the cell Warning Anytime work at the cell is done including making and breaking connections this switch absolutely should be in the off position The 100 V output and high current capability of the 273A make it a dangerous device one capable of causing severe injury or even death The upper Cell key provides the normal Cell ON OFF control during operation Unlike the CELL ENABLE switch this key is subject to software override For example the ON state must be selected before starting a scan However a scan may contain delay intervals to be carried out in the Cell OFF state If this is the case the cell is turned off automatically at the appropriate points in the scan sequence The cell status can be noted at any time by observing the Cell indicator This indicator is unique first in that it is red and second in that it has three states OFF HALF BRIGHT and FULL BRIGHT The significance of each state is OFF Both the CELL key and the CELL ENABLE switch are OFF OR the CELL key is OFF and the CELL ENABLE switch is ON HALF BRIGHT The CELL key is ON but the CELL ENABLE switch is OFF FULL BRIGHT Both the CELL key and the CELL ENABLE switch are ON The cell is ON only when
73. is initiated START key this indicator lights for 1 4 second to advise the operator that the scan sequence has started This may or may not correspond to actually applying E I 1 to the cell For example if the scan program includes a DELAY 1 interval the delay could be done with the cell ON or OFF If the delay is done with the cell ON the lighting of the E I 1 indicator marks the moment when E I 1 is applied If the delay is done with the cell OFF the lighting of the E l 1 indicator means that the programmed scan sequence has been initiated and nothing more 2 DELAY 1 Scans typically but not necessarily begin with a delay interval and the DELAY 1 indicator lights while the delay is in progress If Delay 1 is PASS ed the DELAY 1 indicator doesn t light If the Delay 1 interval is 1 4 second or less the indicator lights for 1 4 second See the description of the E I 1 key for a discussion of the Delay Options 3 SCAN 1 This indicator lights as soon as the scan waveform is applied and remains lighted while it is in progress If the scan is 1 4 second or less the light remains on for 1 4 second If a STEP is applied instead of a ramp the SCAN 1 indicator doesn t light at all 4 E 2 This indicator lights for 1 4 second when the scan or step reaches the vertex potential current E I 2 5 DELAY 2 This indicator lights during the Delay 2 interval If this second delay is PASS ed DELAY 2 doesn t light at all If the delay lasts 1 4
74. isplay options advancing once each time the ENTER key is pressed The choices are 1 Second Display Line Blank 2 Charge in coulombs 3 Log of if LOG is enabled 25 26 4 Status of the scan such as a Delay Time Remaining Delay specified in seconds b Time Remaining Until Drift Measurement Can be Made Delay specified in mV s Alternatively measured drift rate if measurement has taken place c Stop Scan d E Applied or Applied according to the selected mode Error messages can also be displayed on the bottom line These include front panel Error Messages which can be cleared by pressing any key and Remote Error Messages which only occur when controlling the Model 273A from a remote computer Remote Error Messages are in two parts the Error and then the Command that caused the failure Remote Error Messages can only be cleared by taking appropriate action at the remote computer or cycling the power The bottom line display can also be used to scroll through the available Overrides see Section 5 2 4 using the up and down arrow keys This capability becomes available once one of the overrides has been called up for display To the right of the display is a screwdriver adjustment that allows the display s angle to be adjusted for optimum readability o o o o o o o o Fig 5 Model 273A Front Panel Model 273A Potentiostat Galvanostat User s Manual 5 2 2 Overload and E Overload These
75. itch shown beneath the DAC is shown in the fixed reference position in which the reference input to the DAC is the aforementioned 10 24V level When Positive Feedback IR Compensation is enabled a fraction of the voltage developed by the current measurement circuit is fed back as an input to the Control Amplifier through the DAC Thus in this mode the switch beneath the DAC connects the output of the Current Measurement circuit to the DAC s reference input The front panel E MONITOR output is the electrometer signal corrected for the amount of iR compensation as shown in the block diagram 3 2 7 Integration The integration circuitry on the IR Integrator board provides for analog integration of current for short timescale coulometry experiments 50 us lt TMB lt 40 ms The effective time constant for measurements ranges from 40 Ns to 40 ms and is controlled by the ITC command The effective time constant combines with the current range to determine the full scale output of the integrator The GIGAIN command further affects the effective time constants See the ITC command in the Model 273A Remote Programming Command Handbook for more information Longer time scale coulometry experiments TMB lt 40 ms with slowly varying currents may be performed using SIE 1 to collect current directly followed by numeric integration using either INT or IINT commands see the Command Handbook 3 2 8 Analog to Digital The Analog to Digital conversio
76. itored by observing the Scan Status Display When the scan ends either by pressing STOP or by completing the programmed sequence the SCANNING indicator will go out One of the three Scan Status Display Indicators E I 1 E I 2 or E I 3 will remain lighted An Override see Section 5 2 4 determines whether the cell will be ON or OFF HOLDING This indicator lights if the HOLD CONTINUE key has been pressed during a scan Pressing the HOLD CONTINUE key causes the scan to halt until the key is pressed again CONTINUE at which point it resumes and the HOLDING indicator extinguishes If a HOLD occurs when a potential current is applied it will continue to be applied subject to the usual Cell switch and Cell Enable switch constraints This is true if the hold takes place at any time during the scan sequence E I 1 DELAY 1 SCAN 1 E I 2 DELAY 2 SCAN 2 E I 3 If the hold occurs during a delay measured in seconds time is not counted for the duration of the hold If it occurs during a delay measured in drift the drift rate is not measured during the hold If applied during SCAN 1 or SCAN 2 the scan simply halts and the potential current in effect as of the moment of the halt continues to be applied START This key is used to start a scan When it is pressed E l 1 lights and the scan progresses as programmed HOLD CONTINUE This key is used to start a hold interval as described in the discussion of the HOLDING indicator Pressing the key
77. ke the SET OFFSET button on the front panel which resets IOFFSET to the present reading FUNCTION 21 CALIBRATE 273A This function is used to calibrate the Model 273A 6 OVERRIDE This key allows the user to make specific modifications to the setup routines An override is accessed by keying OVERRIDE followed by the number corresponding to the Override wanted At that point the override s name and status are displayed The 1 YES and 2 NO keys are then used to specify the status of the selected override The state can be reversed with the YES or NO key as appropriate 1 YES and 2 NO are dual function keys YES and NO apply to the overrides 1 and 2 belong to the numeric keypad A number of overrides have been provided to extend the Model 273A s flexibility power and ease of operation Although memory space for 90 Overrides has been provided range is 10 to 99 the number actually available is much smaller The first available Override is OVERRIDE 10 the next is OVERRIDE 11 and so forth up to the highest one defined Once one of the overrides has been called up the Scan Setup UP DOWN ARROW KEYS can be used to reach the others via scrolling A brief description of each follows OVERRIDE 10 OFFSET DISPLAY I This Override determines whether Offset as set by the SET OFFSET key in the OUTPUT control group will influence the displayed current If YES OFFSET will affect both the level at the OUTPUT connector and the di
78. l Warning To reduce the risk of potentially dangerous electrical shock this work should only be performed by a qualified service technician and then only with the instrument disconnected from all sources of power At frequencies above 10 MHz these measures may not suffice to prevent radiation from being a problem particularly at VHF frequencies Additional measures will then be required Shielding is generally effective A suitable shield can be constructed using metal foil wire screening or similar materials Once the apparatus is completely surrounded by the shield taking care not to unduly restrict ventilation the only additional requirement is to install low pass filters where lines pass through the shield all openings through the shield should be as small as possible A capacitor between a line and the shield can function as a suitable low pass filter The leads of the capacitor should be as short as possible This requirement is optimally satisfied by using coaxial feed though capacitors In the case of a signal lead it is essential that the capacitor s value be such as to attenuate the interference frequencies without unduly attenuating critical frequency components of the signal itself The need to keep fitter capacitor leads short cannot be overemphasized Long leads establish sizable ground loops and may additionally act as radiating antennae Coaxial cables are a special case in that the cable shield acts as an extensi
79. le Select key second key from the bottom in the CONTROL group Press this key as required to light the SINGLE CYCLE indicator Locate t 1 and i keys in the CURRENT RANGE group Operate these keys as necessary to light the 10 A range indicator AUTO must be OFF adjacent light will be extinguished Locate the OUTPUT SELECT key bottom key of OUTPUT group Operate this key as necessary to light the LINEAR indicator Set the CELL ENABLE switch to the ON position Press the CELL ON key lighting the associated indicator Press the ENTER key as many times as are required to blank the bottom line of the display The Model 273A is now ready to run the experiment The programmed sequence will be initiated in the following step Press START The following should be observed Note START can be pressed at any time to restart the check sequence The E I 1 indicator scan status display at upper left hand corner of the front panel will flash once indicating that the initial potential has been applied This potential 0 V and the resulting current 0 A will be indicated on the upper display line Note There is always some small deviation from the nominal value For purposes of these initial checks a normal current indication will be within 1 of the selected current range range is 10 pA 1 of that is 100 nA Potential indications should be within 10 mV of the indicated value The DELAY 1 indicator scan status display will light an
80. maximum versatility in experiment definition An optimally human engineered Scan Setup section is provided to allow cyclic staircase voltammetry corrosion experiments and other pulse and staircase waveforms to be easily performed The alphanumeric liquid crystal display assists in setting up an experiment and in presenting real time data A Scan Status Display additionally provides continuously updated status information as the experiment advances A simple touch of a button implements such advanced features as automatic current ranging and current interrupt IR compensation BNC connectors on the front and rear panels make all pertinent signals available for analog recording Remote Computer Control By interfacing the Model 273A to an external computer via the GPIB or RS 232C Interface complete remote control of the instrument is readily accomplished using the Electrochemical Command Set a group of over 100 mnemonic software instructions specifically developed for electrochemical measurements These commands place unprecedented flexibility in the hands of the electrochemist They provide Access to all front panel functions Control of all timing functions Application of pulse and staircase waveforms Automatic acquisition of data with or without current auto ranging Data averaging in real time Internal storage and arithmetic data manipulation These commands and all necessary instructions for operating the Model 273A via an external com
81. multiplexed as well as the type of signal applied full ac dc signal or ac signal only The Model 273A Remote Programming Command Handbook describes the computer commands used with the Model 273A 92 option 5 3 12 RS 232C Interface This connector and the associated switch assembly are used to establish serial RS 232C communications between the Model 273A and a host computer Instructions for remote operation are given in the separately bound Model 273A Remote Programming Command Handbook The adjacent switch assembly sets the user controlled RS 232C parameters See Appendices A and D of the Command Handbook for additional information 5 3 13 IEEE 488 GPIB Interface This connector and the associated switch assembly are used to establish communications between the Model 273A and a host computer via the GPIB port IEEE 488 Instructions for remote operation are given in the separately bound Model 273A Remote Programming Command Handbook The adjacent switch is used to set the GPIB address and TEST ECHO status and allows for selection of the terminator See Appendices B and C of the Model 273A Command Handbook for detailed information 5 4 Differential Electrometer The electrometer Fig 9 acts as the interface between the Model 273A and the reference electrode A cable runs from the Electrometer Housing to the CELL INTERFACE connector at the back of the Model 273A The various leads switches and jacks on the front of the housing are
82. n section of the instrument has the ability to digitize any one of four applied signals The output of the Current Measurement Circuit Signal in the block diagram The signal after processing by the iR Integrator circuit Q Signal in the block diagram The Electrometer Output E Signal in the block diagram An Auxiliary A D Input Aux A D Signal in the block diagram BOD The A D section incorporates a low pass filter for the signal only a computer selectable gain of ten for both the E and signals and a computer selectable additional gain of five for all four signals E I AUX and Q The X2 X10 buffers output is applied to a Sample and Hold circuit which in turn drives a 12 bit A D Converter that connects to the bus The A D Converter prior to the gains has a nominal full scale range of 10 V in MEASURE E 2 times full scale current in MEASURE I and 10 V in AUX A D The gain settings made further on are always relative to these base values Both the E and signals can be offset by the SUPDAC before applying the gains to the signal This allows the measurement of small differences on top of large dc values 3 2 9 OUTPUT and AUX DIGITAL Connector The OUTPUT provides a voltage proportional to the current or to the computer calculated quantities of charge and log current This is also the signal applied to the Y axis at the RECORDER INTERFACE connector The AUX DIG I O interface is used for experimental control and
83. nce is 1 kQ It is inverted with respect to the applied potential For example if the applied potential is 1 V the potential at the E MONITOR connector will be 1 V Note that the potential at the rear panel ELECTROMETER MONITOR connector is also inverted with respect to the applied potential 5 2 13 CURRENT RANGE Group There are three keys nine indicators and one BNC connector in this group Their function is to set and monitor the Model 273A s full scale current range One of the eight available current ranges is always selected and the corresponding indicator lit A cell current equal to the selected current range gives 1 V at the MONITOR connector A current of two times the current range generates an OVERLOAD condition except on the 1 A range where the limit is 1 A Model 273A Potentiostat Galvanostat User s Manual The polarity of the voltage at the MONITOR connector is that of the current linear output mode For example a current level of 1 mA will give 1 V at the MONITOR connector 1 mA Current Range representing an anodic or reducing current There are two selection modes MANUAL and AUTO In the MANUAL Mode the range is selected with associated arrow keys The 1 1 key moves the selection upwards through the available ranges The key moves it downwards In the AUTO mode the Model 273A automatically seeks the current range that causes the MONITOR Output to be between 15 and 190 of full scale that is betw
84. nected the 273A is allowed unimpeded transmission 7 Logic Ground Data signal levels should be with reference to logic ground The logic ground line of the 273A should interconnect with the logic ground line of the computer EI aa 11 5 V Unless 5 V 100 mA max is needed by the connected apparatus don t connect to this pin In no case should this 5 V level be tied to the 5 V level in the computer 5 V can be used to continuously assert the Clear to Send Line pin 5 allowing the 273A to transmit at any time Ee se Elk Note that the 273A RS 232C port is configured as a female DTE port Data Terminal Equipment rather than as a DCE Data Communications Equipment Thus cabling to most microcomputers can be accomplished with a standard reversed or switched RS 232C cable also known as a null modem cable 58 Model 273A Potentiostat Galvanostat User s Manual APPENDIX B RACK MOUNTING The Model 273A can be mounted in a standard 19 inch relay rack by means of the Princeton Applied Research 1715 0206 Rack Mounting Kit This kit consists of two special side panels with integral mounting flanges and four screws To install the kit proceed as follows 1 Remove the side panels from the instrument Each side panel is secured by four screws DO NOT DISCARD THESE SCREWS 2 Mount the side panels supplied with the kit The flanges should go toward the front and turn outwards Secure each panel with SIX screws You will need the
85. nnot exceed 10 V and currents larger than two times full scale will cause an overload condition For example Chapter 5 Operating Instructions 47 5 3 Rear Panel In addition to the ac power fuse assembly Chapter 2 there are numerous connectors and two switch assemblies located on the rear panel Fig 8 A brief description of each follows Pinouts for the multi pin connectors are provided in Appendix A 48 on the 1 mA current range assuming a Log Reference of 3 1 mA would give 0 V 100 HA would give 1 V 10 uA would give 2 V and so forth Currents larger than the Log Reference Range give positive outputs In the example being considered a current of 2 mA would give 0 301 V on the 1 mA range a current of 10 mA would give 1 V and a current of 100 mA would give 2 V These relationships hold for both automatic and manual current ranging The maximum possible voltage in any case is 10 V The smallest change is 5 mV 1 part in 2000 COULOMBS In this mode a full scale current for one second on the current range in effect when RESET INTEGRAL is pressed will give 10 V out For example if on the 1 mA range the current was 1 mA for 1 s the OUTPUT voltage would be 10 V representing one millicoulomb of charge At that point the output scaling would decrease by a factor of ten In the example after one second the output would reach 10 V and then immediately drop to 1 V as the scaling shift occurs The voltage would then
86. oaches the rest potential When the actual rate becomes slower than the rate specified via the mV SEC key the delay interval ends The slower the specified drift rate the longer the minimum delay time the longer it takes to get a valid drift rate reading Example To set a DELAY 2 drift rate of 0 01 mV s key DELAY 2 0 1 mV SEC ENTER CELL OFF This key determines whether delay intervals specified in seconds will be done open cell or with the specified potential current applied The key is a toggle that is its state indicated by the alphanumeric display reverses each time the key is pressed Example To set an open cell DELAY 1 of 100 s key DELAY 1 1 0 0 SEC CELL OFF ENTER ENTER This key has two functions First it enters newly specified parameter values into the setup program Second when not entering a parameter it allows different kinds of information to be scrolled through the bottom line of the display For example when a setup parameter key is pressed the set value is displayed together with the message ENTER XXX XXX signifies the parameter The new value can then be keyed and ENTER pressed after which the new value will be displayed Pressing ENTER again clears the new value from the display and establishes the scroll mode in which the bottom display line scrolls through several possible display options advancing once each time the ENTER key is pressed The choices are a Second Display L
87. ol and ground RS 232C INTERFACE Serial port for control of the Model 273A from an external computer Associated switch assembly sets RS 232C parameters exception Terminator lt CR gt or lt CRLF gt is set by switch in the GPIB switch assembly Note The maximum potential that can be applied to this port is 15 V The Model 273A Remote Programming Command Handbook describes switch settings and communications protocols IEEE 488 GPIB INTERFACE Parallel port for control of the Model 273A from an external computer Associated switch assembly sets GPIB Address Terminator and status of Test Echo function The Model 273A Remote Programming Command Handbook describes switch settings and communications protocols AC OUTPUT used only in units equipped with the 273A 92 Electrochemical Impedance Interface option Outputs the ac current signal from the test cell The signal is controlled by commands from an external computer via the GPIB or RS 232C port Chapter 3 Characteristics 13 10 AC E OUTPUT used only in units equipped with the 273A 92 Electrochemical Impedance Interface option Outputs the ac voltage signal from the test cell The signal is controlled by commands from an external computer via the GPIB or RS 232C port 11 MULTIPLEXED OUTPUT used only in units equipped with the 273A 92 Electrochemical Impedance Interface option Either a current or voltage signal can be output from this connector as determined by commands from
88. on LL 32 GELL GABLE rr Se be bo be Dae a 7 Cell Cable Leads 52 CELL ENABLE key 7 CELL ENABLE pushbutton 21 CELL Group 4 33 Ka KAP ETIKA RABE BOET Bee 38 Cell indicator LL 39 Cell indicator brightness 7 FULL BRIGHT 7 HALF BRIGHT 7 OFF stone cc o BE RR ESE 7 Cell Indicator FULL BRIGHT 39 Cell Indicator HALF BRIGHT 39 Cell Indicator OFF oooooooooooo 39 CELL INTERFACE 13 49 55 CELL INTERFACE connector 51 GELIKEV tannic PAETE HER BAR AR BEER BE Di 38 Cell Off at End SS SS ee 32 CELL Switch 16 CIFGUITV eo SE sees BEES BEDE BEER BEES 18 Analog EER EER ariana 18 BUS 55 BE SE BEE BEES RD ES 18 Computer Interfaces 12 Connectors Front Panel 12 Rear Panel 13 CONTINUOUS CYCLE 37 CONTROL Group 00000 e eee eee 36 convention ees 3 Polarity 625252555255 Sees 3 Correct Displayed E 32 Goulombs sia EE AO ami Nana Nana 13 Coulombs Indicator 32 Current Interrupt IR Compensation 44 advantages and disadvantages 45 CURRENT INTERRUPT key 46 CURRENT INTERRUPT PERCENT CORRECTION bp sera eB wy Br CN are NG a TO a 31 CURRENT RANGE Group 46 Current Range Selection 47 AUTO sgema tata a a
89. on of the enclosure shield This being the case the filter can be mounted in a shielded box fitted with coaxial connectors without undue concern for keeping the box extremely dose to the enclosure If more convenient to do so it can be located at some distance from the enclosure as long as the integrity of the coaxial shield is maintained The techniques described are extraordinary measures that should be required for unusual cases only If they are applied with care radio frequency interference should be reduced to an acceptably low level in all but the most critical applications However if these techniques are applied incorrectly the efforts to reduce the interference could prove disappointing Users are advised to contact the factory for advice in the case of a problem that does not yield to these measures 2 8 Transient Sensitivity Generally speaking the design and construction techniques used in equipment manufactured by Princeton Applied Research are conducive to assuring normal operation in the presence of moderate transient levels Although these provisions are sufficient for operation in most places where this equipment is used it is certainly possible for transient levels in particular Chapter 2 Safety Considerations 9 10 environments to be so severe as to make reliable operation uncertain High level transients are of three general types 1 Static Discharge Transients from this source generally affect input or outpu
90. onnector This output is NOT corrected for Ry compensation unlike the front panel E MONITOR Output The output impedance is 1 kQ Note that this potential is inverted in sign with respect to the applied cell potential 5 3 7 AC Output This connector used only in units equipped with the 273A 92 Electrochemical Impedance Interface option outputs the ac current signal from the test cell The signal is controlled by commands from an external computer via the GPIB or RS 232C port refer to the Model 273A Remote Programming Command Handbook 5 3 8 AC E Output This connector used only in units equipped with the 273A 92 Electrochemical Impedance Interface option outputs the ac voltage signal from the test cell The signal is controlled by commands from an external computer via the GPIB or RS 232C port refer to the Model 273A Remote Programming Command Handbook Model 273A Potentiostat Galvanostat User s Manual 5 3 9 Multiplexed Output This connector is used only in units equipped with the 273A 92 Electrochemical Impedance Interface option Either a current or voltage signal can be output from this connector as determined by commands from an external computer via the GPIB or RS 232C port refer to the Model 273A Remote Programming Command Handbook Multiplexing is accomplished by alternating the operand of the MIE command between 1 and 2 on successive iterations Note This output is intended for use with Princeton Applied Research
91. ontrolled potential mode 3 Pres E I 1 The display message line will indicate that the E I 1 is to be entered Then key 0 ENTER entering O V as the programmed starting potential for the scan to be performed 4 Press DELAY 1 The display message line will indicate that DELAY 1 is to be entered After that key 1 0 SEC ENTER entering 10 s as the time for which E I 1 0 V will be applied before beginning the scan Note the message at the end of the lower display line It should indicate that the delay will be performed with the cell off If it indicates the CELL ON state press the Scan Setup CELL OFF key to establish the desired CELL OFF delay 5 Press SCAN 1 The display message line will indicate that SCAN 1 is to be entered Next key 2 0 ENTER entering 20 mV s as the programmed scan rate for the first leg of the scan 6 Press E I 2 Then key Model 273A Potentiostat Galvanostat User s Manual 10 11 12 13 14 15 16 1 0 0 0 ENTER entering 1 000 V as the scan vertex potential Press DELAY 2 Then key 1 0 SEC ENTER establishing 10 seconds as the time for which the vertex potential will be applied Press SCAN 2 Then key 2 0 ENTER establishing a scan rate of 20 mV s for the second leg of the scan as well Press E I 3 Then key 0 ENTER establishing the scan end potential at 0 V which was also the starting potential Locate the Cyc
92. operation E I 1 specifies the potential current applied at the start of the scan E l 2 specifies the potential current applied at end of the scan s first leg In Half Cycle mode operation the scan ends at E l 2 and E l 2 continues to be applied In Single Cycle operation E l 2 is a vertex and E l 3 specifies the final potential which continues to be applied after the scan is over In continuous operation there is repetitive cycling between E I 2 and E I 3 until the STOP key is pressed DELAY 1 and DELAY 2 may be used to determine the length of time E l 1 and E l 2 are applied PASS 4 ms The Delay at E I 1 and E I 2 may be carried out with the cell either on or off If off E I 1 or E I 2 is applied after the Delay has expired The delays may also be specified as drift rates in mV s See DELAY and DELAY 2 for details The units and resolution are indicated by the display Potential can be specified to the nearest mV Potentials can be set over a range of 10 V to 10 V However no given scan can span more than 4 V absolute In other words the difference between the highest potential minus the lowest potential cannot exceed 4 V Current is specified as a fraction of the selected CURRENT RANGE up to a maximum of two times the current range one times on the 1 A range Examples a To set and enter an Initial Potential of 0 250 V key E I 1 2 5 ENTER Model 273A Potentiostat Galvanostat User s Manual The
93. or at least 24 hours before applying power C Altitudes to 50 000 feet 5 5 3 International Standards This equipment is designed to meet or exceed the requirements of the following standards A BS EN55022 1987 Class B B BS EN50082 1992 1 IEC 801 2 1991 2 IEC 801 3 1994 3 IEC 801 4 1988 C BS EN61010 1 1995 Installation Category II Pollution Degree 2 Model 273A Potentiostat Galvanostat User s Manual APPENDIX A PINOUTS A 1 Cell Interface 36 pins RR FOND E Guard Driven 24 V 100 mA maximum 24 V 100 mA maximum Electrometer Shield gnd Electrometer Output Potential 15 x Ejes Eworking A 2 Recorder Interface mating connector DP15P omo n E E I 55 Notes The E MONITOR and OUTPUT lines are driven by the same signals as are present at the front panel E MONITOR and OUTPUT connectors When operating under front panel control the Pen Drop relay contacts close when START or CONTINUE is pressed Pressing STOP or HOLD causes the contacts to open Under computer control RS 232C or GPIB port the pen contact closure is controlled by the PEN command A 3 Auxiliary Interface mating connector DB9S 56 This connector provides several functions only available when the Model 273A is being controlled from an external computer via the RS 232C or GPIB IEEE 488 port Included are the signals required to drive a Model 303A Static Mercury Drop Electrode If this
94. ostat Galvanostat User s Manual 5 OPERATING INSTRUCTIONS 5 1 Introduction Although the Model 273A is a complex microprocessorcontrolled analytical instrument its operation is nevertheless straightforward The instrument s front panel has been carefully designed with attention to humanengineering considerations Its two line alphanumeric display continuously displays the potential and current on one line while guiding the operator through the operating sequence via messages displayed on the second A special Scan Status Display is provided that continuously indicates the stage in progress of an ongoing scan Front panel indicator lights allow the user to ascertain the setup at a glance A battery powered parameter backup system retains all selections and parameter values When the 273A is powered up all selections and parameter values are as they were at the end of the previous operating session The default values can however be restored by reinitializing the system via FUNCTION 10 The use of FUNCTION 10 is described in Section 5 2 4 Another way to restore the default values is by pressing the LOCAL key when powering up The key must be held in until the message SYSTEM REINITIALIZED appears on the front panel display No effort has been spared to make the Model 273A an easy instrument to operate Nevertheless information beyond that provided on the front panel is required for optimum performance in many situations This chapter of
95. ostat Galvanostat features both front panel and computer control for virtually unlimited flexibility and utility It uses the latest analog and microcomputer design advances to provide high performance ease of use and greater versatility in electrochemical measurements The instruments 100 V compliance and 1 A output capability allows rapid and accurate potential or current control in virtually any electrochemical cell The high compliance voltage is particularly important in maintaining potential control when working with high resistance dilute electrolytes or non aqueous solvents Moreover it enables faster charging of the cell capacitance allowing the potentiostat to rapidly respond to step transitions in the control potential Component selection shielding grounding and circuit design are all carefully optimized for minimum internal electronic noise giving high sensitivity and a quiet output signal A low pass filter facilitates dealing with noise arising in the cell itself The Model 273A uniquely addresses the critical question of stability versus speed The user can select a HIGH SPEED mode to take advantage of the potentiostat s extraordinarily fast rise time Alternatively the user can select the HIGH STABILITY mode for oscillation free operation with almost any cell A high performance four terminal current to voltage converter circuit is inducted for accurate rapid low drift current measurements free of degradation from cell c
96. oth delays to PASS d Establish the Cell ON state CELL ON and CELL ENABLE Then press START to apply the square wave to the cell The cell should be completely set up for the measurements to be made Any change at the cell will probably change Ru e Monitor the MONITOR connector with an oscilloscope The Model 273A should be set to the same current range as will be used in the forthcoming measurement If the Current Range setting is changed the actual value of IR compensation can change as previously discussed At the oscilloscope use internal triggering and display the waveform so that the waveform s risetime can be readily observed A horizontal deflection factor of 2 ms per division will generally give good results f Press SET IR so that the set value of R it should be 0 is displayed on the Model 273A g While observing the displayed waveform on the oscilloscope hold in the Scan Setup 1 key The R compensation will increase causing the decay intervals in the displayed waveform to become shorter The longer the key is held in the greater will be the applied compensation The actual value can be directly read from the Model 273A display Figure 6 illustrates the compensation s effect For optimum stability the rise time should be as fast as possible without ringing When the uncompensated resistance is about 90 to 95 compensated the waveform will show a smooth decay with perhaps just a bit of undershoot This Ch
97. ower Cord Plug with Polarity Indication 5 Caution The apparatus described in this manual may be damaged if it is set for operation from 110 V ac and turned on with 220 V ac applied to the power input connector A detailed discussion of how to check and if necessary change the power voltage setting follows The Model 273A can operate from any of four different power voltage ranges 90 110 V 110 130 V 210 230 V and 230 260 V 48 62 Hz Change from one voltage range to another is made by repositioning a plug in circuit card in the rear panel Line Cord Fuse Assembly Instruments are ordinarily shipped ready for operation from 110 130 V ac unless destined for an area known to use a line voltage in a different range If this is the case they are shipped configured for operation from the other range If necessary the change from one range to another can be accomplished in the field Changing the voltage range or changing the line fuse should only be done by a qualified service technician and then only with the instrument disconnected from all sources of power Observing the instrument from the rear note the clear plastic door immediately adjacent to the power cord connector Fig 2 When the power cord is disconnected from the rear panel connector the plastic door is free to slide to the left giving access to the fuse and to the voltage selector circuit card Fig 2 Power Input Assembly The selector card is located a
98. puter are described in the separately bound Model 273A Remote Programming Command Handbook The Model 273A is fully equipped with the necessary hardware to implement experiments from your computer including Two 14 bit digital to analog converters for versatile waveform generation A 12 bit analog to digital converter to measure current and potential An on board microprocessor to perform the experiment defined by the Command Set On board memory to store the programmed parameters and data point values When the programmed experiment is finished the data can be transferred to the computer for plotting or further processing 2 Model 273A Potentiostat Galvanostat User s Manual 1 4 Polarity Convention The Model 273A follows the American polarity convention and the display indications are consistent with that convention Positive current is catholic that is a current is defined as positive if reduction is taking place Negative current is anodic that is a current is defined as negative if oxidation is taking place In potentiostatic operation making the applied potential more positive will make the current tend to be more anodic Conversely making the applied potential more negative will make the current tend to be more catholic This is true for all potential sources including EXTERNAL INPUT In galvanostatic operation making the applied current more positive by any means except applying a potential to the EXTERNAL INPUT will tend
99. r cord plug provided is of the type illustrated in Fig 1 If this plug is not compatible with the available power sockets the plug or the power cord should be replaced with an approved type of compatible design Warning If it is necessary to replace the power cord or the power cord plug the replacement cord or plug must have the same polarity as the original Otherwise a safety hazard from electrical shock which could result in personnel injury or death might result In many parts of the world commonly used power plugs and sockets differ from those in general use in the United States For this reason cords supplied with units to be used outside the United States may not be furnished with a power plug making it necessary for the user to obtain and install a power cord plug suited to use in their area For safety it is necessary that normal polarity relationships be maintained The wires in the supplied power cord are color coded for this purpose Whatever the actual plug configuration the black wire should be the line or active conductor also called live or hot the white wire should be neutral and the green wire should be earth ground 2 3 Power Voltage Selection and Line Fuses Before plugging in the power cord make sure that the equipment is set to the voltage of the ac power supply LINE OR ACTIVE CONDUCTOR ALSO CALLED LIVE OR HOT E NEUTRAL OR IDENTIFIED CONDUCTOR EARTH OR SAFETY GROUND Fig 1 P
100. r keyed is the exponent if the current range were expressed in engineering notation in units of amperes The default value is 0 1 A range For example suppose one wished to specify the 1 uA range The sequence would be 1 Key FUNCTION 1 2 ENTER The message ENTER LOG REFERENCE will be displayed 2 Key 6 ENTER to specify the 1 HA current range With this setting a current of 1 UA will yield O V at the OUTPUT connector in LOG mode operation FUNCTION 13 ENTER INTERRUPT This function is used to specify the frequency with which current interrupts are performed if operating with Current Interrupt IR Compensation with the instrument under front panel control The interrupt period is specified in units of seconds from 004 s to 30 s with the default corresponding to 1 s Example To set a current interrupt period of one second proceed as follows 1 Key FUNCTION 1 3 ENTER The message ENTER IRUPT will be displayed 2 Key 1 ENTER to specify an interrupt interval of one second FUNCTION 14 OUTPUT TIME CONSTANT This function provides a digital low pass 6 dB octave filter at the front panel OUTPUT connector The time constant range for the filter extends from 0 to 30 seconds The default value is 0 FUNCTION 15 PEN DELAY This function allows the user to control the pen drop delay When a scan is initiated the pen has to move to the starting coordinates Should the pen drop during this homing operation
101. ress values in engineering notation see 6 for examples simply sets the decimal point As many as three digits can follow it 9 sets the polarity As an expression is keyed it has a positive value The first time that is pressed independent of the parameter s previous polarity it sets the parameter negative Each subsequent time the key is pressed the polarity reverses Note that can be pressed at any time prior to pressing ENTER However in an expression containing EXP once EXP is keyed the sign will only affect the polarity of the exponent 10 1 and These keys have a three fold function First during the setup process they can be used to make small adjustments in the value of the displayed parameter Each time an arrow key is pressed an incremental change occurs 1 mV for potential 0 1 for current If the key is held in the parameter value increments or decrements continually The rate of change increases by a factor of ten if the key is held in for several seconds It is not necessary to press the ENTER key to execute the change Second they can also be used to increment or decrement a parameter during an actual scan The active parameter is the one operated on Third they can be used to scroll through the various Override messages The user can bring one Override message to the screen and then use the arrow keys to scroll through the available choices to reach the one of int
102. rise linearly with charge until 10 V was reached again this time indicating ten millicoulombs At that point another factor of ten scaling change would take place and the cycle would repeat This process can repeat as many times as necessary for any practical experiment The current integral in coulombs can be displayed if desired with continuous updating as the measurement progresses Recall that one of the functions of the ENTER key is to control the bottom line display If anodic to cathodic crossover occurs during the measurement the coulometer will reverse direction and downrange if necessary Current Range changes that occur either manual or automatic will have no effect on the voltage at the OUTPUT connector in coulometer operation For best results the starting current range the one in effect when RESET INTEGRAL is selected should be that which yields the highest on scale current reading RESET INTEGRAL This key causes the final current integral in coulombs to be displayed At the same time the coulometer is reset to zero and the initial scaling factor as set by the selected Current Range is established Note The reset state is maintained for three seconds or until the RESET INTEGRAL key is released whichever is longer At that point charge accumulation begins again SET OFFSET This key allows one to specify a current that is internally subtracted from the cell current The offset is specified in units of
103. s in the working electrode lead certainly reasonable at low current levels simply connect the shorting plug between the two jacks If the decision is to eliminate this source of error simply bring a lead from the Sense jack directly to the working electrode One connection or the other should be made never both In galvanostatic operation one could conceivably choose not to monitor the potential with a reference electrode and so not use the electrometer Where this is the case no harm would come by operating with the Sense jack open However it is just as easy and preferred to install the jumper If the potential is monitored the same remote cell versus local electrometer sense considerations apply The measured potential is affected by the iR drop 4 ELECTRODE LEADS There are three leads each terminated in a clip The leads can be readily identified by the color of the clip s insulating boot Green identifies the Working Electrode and red the Counter Electrode Warning Potentials as high as 100 V could be present at the counter electrode lead s clip For safety always have the front panel cell enable switch in the off position when handling the electrometer leads The polarity of the potential at the counter electrode will be opposite the applied potential This is necessary to establish the correct polarity relationship at the working electrode versus the reference electrode Black identifies the ground lead It can b
104. second or less the light remains on for 1 4 second 6 SCAN 2 This indicator lights during the second leg of the scan If the scan is 1 4 second or less the ight remains on for 1 4 second If a STEP is applied instead of a ramp SCAN 2 doesn t light 7 E 3 This indicator lights for 1 4 second at the end of the scan indicating that the programmed sequence has been completed Note If the entire scan is too quick to be displayed in real time by the LED s the LED s that correspond to the selected states light in sequence to show the operations performed The timing of this display sequence is not linked with that of the scan Chapter 5 Operating Instructions 27 28 5 2 4 SCAN SETUP Group This set of thirty keys is used to set the parameter values and sequences for experiments performed with the Model 273A When one parameter key is pressed the set value is displayed second line of display together with the message ENTER XXX where XXX is the parameter of interest To change a parameter simply key the new value and press ENTER The new value replaces the previous one and is displayed Note Throughout the following text brackets are used to denote a key to be pressed For example ENTER designates the Enter key To simply check a parameter value press the corresponding setup key and note the displayed value Press any other key to leave the operation ENTER is a good choice because its only effect will be to reinstall
105. selection and safety information 9 Set the 273A s POWER ON OFF switch to ON 10 Reinitialize the system by pressing the following sequence of keys FUNCTION 1 0 YES ENTER 4 4 Procedure 22 The following steps program the Model 273A to do a controlled potential experiment on the 100kQ dummy cell resistor located in the electrometer housing A scan starting at 0 V advancing to 1 V and then returning to 0 V will be applied The current in the resistor will track this voltage starting at zero increasing to 10 A and then decreasing to zero again A voltage corresponding to this current will appear at both the MONITOR connector and at the OUTPUT connector With a selected current range of 10 uA the voltage at these connectors will start at O V increase to 1 V tracking the scan and then return to 0 V The current in the resistor will be displayed throughout the experiment Note The dummy cell resistor has a 1 tolerance rating As a result the current indications can be at least 1 off with respect to the values indicated in this procedure Note also that residual drift or noise in the Model 273A itself can contribute a small additional 1 Note the Model 273A display There are two information lines The measured cell current and potential are displayed on the upper line The lower line displays various messages 2 Press the POTENTIOSTAT key The associated indicator should light indicating that the 273A is in the c
106. sociated indicator will light and positive feedback compensation will be established Note This pushbutton is a toggle to turn the compensation off simply press POSITIVE FEEDBACK again 2 R NOT KNOWN Model 273A Potentiostat Galvanostat User s Manual a Press SET IR Then key and enter an R of O It is always advisable to start with zero IR compensation With a higher starting value there is a definite risk factor in that the system may oscillate when the Positive Feedback Mode is activated HIGH POWER HIGH AMPLITUDE OSCILLATIONS CAN BE DESTRUCTIVE AND DEFINITELY SHOULD BE AVOIDED b Press the POSITIVE FEEDBACK key establishing Positive Feedback mode operation c Program the Model 273A to apply a 62 5 Hz 50 mV square wave to the cell The following parameter values can be used Note The 50 mV figure is not critical Smaller or larger amplitudes if more appropriate to the chemistry can be used Note If LINE SYNC is ON OVERRIDE 14 the frequency will be 15 Hz 60 Hz power or 12 5 Hz 50 Hz power The procedure will generally be easier to perform with the LINE SYNC off less flicker on the oscilloscope display E 11 0 05 V with respect to the potential of interest DELAY 1 PASS see Note SCAN 1 STEP E 12 0 05 V with respect to the potential of interest DELAY 2 PASS see Note SCAN 2 STEP E 13 0 05 V with respect to the potential of interest Control Mode CONTINUOUS Note 62 5 Hz rate results from setting b
107. splayed current If NO default status only the level at the OUTPUT connector will be affected OVERRIDE 11 UPDATE COULOMBS This override determines whether the coulombs indication will be periodically updated as the experiment progresses If YES default status the displayed coulomb accumulation will be updated every timebase If NO coulombs are not measured NO is normally selected if speed of data acquisition is the main concern such as might be the case in remote control experiments If the Model 273A is being controlled from an external computer via the RS 232C or GPIB inter face the rate at which data can be taken will be faster with this override in the NO state OVERRIDE 12 CORRECT DISPLAYED E This override determines whether the displayed potential will be affected by the IR compensation If YES default state the displayed potential will be corrected for IR drop assuming that IR Compensation is in use the same as the potential at the E MONITOR and recorder outputs If NO any errors due to IR drop will affect the displayed potential as well even though IR Compensation is in use Note IR drop errors always affect the rear panel ELECTROMETER MONITOR output whether or not IR Compensation is active OVERRIDE 13 CELL OFF AT END This override determines the Cell ON OFF status at the end of a scan If YES the cell will be turned off counter electrode connection interrupted at the end of the scan If NO the counter electro
108. t circuits Input circuits that include MOS field effect transistors to achieve a high input impedance are particularly susceptible to damage from this source Damage typically occurs when the charge built up on a user s body discharges into an input or output connector as a connection is being made Among the factors determining the tendency for charges to build are the kind of clothing fabrics worn shoe materials and the materials in the floor or floor covering High Level Transients Generated Internal to the Place of Use Such transients almost always enter the instrument via the line cord Possible sources include heavy duty electric motors rf equipment lasers diathermy machines arc welders spark chambers and others Lightning Unless the equipment is connected to remote sensors or other devices so located as to be vulnerable to lightning strikes transients caused by lightning almost always enter the instrument via the line cord Static discharge problems can sometimes be avoided by judiciously selecting the floor covering in the work area The simplest approach to the problem is to discharge one s body by touching a grounded metal object just before touching the instrument particularly when making connections to it Transients that enter the instrument via the line cord can generally be suppressed by external line transient filters Suitable devices are commercially available Model 273A Potentiostat Galvanostat User s Manual 3 CHA
109. t itin a standard 19 in 47 5 cm rack assembly Instructions for rack mounting are provided in Appendix B 2 Set the Model 273A s POWER ON OFF switch to the OFF position 3 Set the Model 273A CELL ENABLE pushbutton switch to OFF 4 Conned the Electrometer Cell cable to the CELL INTERFACE connector at the rear of the Model 273A Bring the electrometer around to the side of the Model 273A for easy access 5 Locate the shorting plug supplied with the electrometer Plug it into the SENSE gray and WORKING green electrometer jacks shorting them together 6 Set the switch located on the Electrometer to the DUMMY position In this position an internal resistor acts as the cell Note This is a locking switch To change its setting the toggle must be pulled out a millimeter or two as required to disengage the locking mechanism 7 Note the GROUND COUNTER ELECTRODE and WORKING ELECTRODE leads that emerge from the electrometer In the following checks take care that the alligator clips at the end of the leads don t short to each other or to any electrically conducting material Warning Although the external cell is disconnected when the electrometer switch is set to DUMMY the potential on the Counter Electrode lead can be as high as 100 V and must be considered dangerous in case the switch is accidentally set to EXT ES EE EE EE EE EE EE EE O 21 Plug the Model 273A into a suitable source of ac power See Chapter 2 for line voltage
110. t selection is 10 us on the 1 A and 100 mA Current Ranges and 75 us on all other Current Ranges Model 273A Potentiostat Galvanostat User s Manual Note The default values give good results in many applications Do not change these values using the applicable functions unless you are well grounded in current interrupt IR compensation theory This is particularly true of functions 17 18 and 19 A prerequisite to evaluating these parameter selections is that an oscilloscope be connected to the rear panel electrometer monitor connector to observe the current interrupt waveform as discussed in the following paragraphs Even using the oscilloscope it is not easy to make optimum determinations The position of the selected points as well as the path of the projection through the points must be estimated Figure 7 illustrates the rear panel ELECTROMETER MONITOR waveform for a typical Current interrupt cycle Referring to the figure note that a fast potential drop equal to iR occurs at the moment of interrupt The purpose of the routine is to measure this drop so that Ry can be calculated and a correction factor developed POTENTIAL PRIOR TO INTERRUPT POTENTIAL AFTER INTERRUPT RECONNECT FIRST iRy PROJECTION THROUGH SELECTED POINTS SECOND ERROR CORRECTABLE BY ADJUSTING CORRECTION RECONNECT gt TWO POINTS ARE PROJECTED ELECTROMETER MONITOR POTENTIAt TIME gt Fig 7 Current Interrupt Waveform at Ele
111. t the lower edge of the fuse compartment A number printed on the upper surface of the selector card is visible without removing the card The number is somewhat obstructed by the fuse but can be read if the viewing angle is just right This number indicates the selected nominal line voltage There are four numbers on the card but only one is visible In other words the card can be inserted in any of four different positions and a different number can be read in each A table printed on the rear panel of the Model 273A adjacent to the power input assembly indicates the actual line voltage range for each number If the number showing is incorrect for the prevailing line voltage the card will have to be repositioned as follows The first step is to remove the fuse When the lever labeled FUSE PULL is rotated out and towards the left the fuse will lift so that it can be easily removed At the front center of the circuit card is a small hole that serves as a convenient pry point Needle nose pliers or a paper clip can be used as an aid in removing the board With the board removed four numbers become visible 100 120 220 and 240 Orient the board so that the desired number Table 1 will be visible when the board is inserted Then insert the board into its connector The selected number should be the only one that shows Be sure the board is securely seated in its connector Model 273A Potentiostat Galvanostat User s Manual Table 1 Voltage Select
112. table and may even oscillate Once R is entered Positive Feedback IR Compensation can be activated Resistance values have a resolution limited to 0 1 of the current measuring resistor associated with the Current Range Thus the accuracy of the value that is actually Programmed can vary with the Current Range Moreover as a result of this resolution limit the value in effect can change during the experiment if the Current Range changes either manually or automatically For this reason care should be taken when using this feature with autoranging The resistance resolution limit and maximum compensation as a function of Current Range is Chapter 5 Operating Instructions 41 42 RANGE COMPENSATION LIMIT Consider how the resolution limit affects the accuracy of the programmed value For example assume a resistance of 1 234 KO is entered on the 100 A range On that range the resistance resolution is 10 Q giving an actual programmed resistance of 1230 Q In other words the programmed resistance differs from that entered front or rear panels by 4 Q Let us continue with this example to see how error due to the resolution limit can occur when the current range changes If during the experiment the current range changes to 1 mA where the resistance resolution is 1 Q the actual programmed resistance will change to 1234 Q The improved resolution allows the actual programmed value to be identically that originally entered Although this
113. the light is at full brightness Chapter 2 Safety Considerations 7 Users might note that there is also a Cell switch at the electrometer This switch has two positions DUMMY and EXT Its function is to determine whether the Model 273A is controlling with respect to the external cell or with respect to an internal dummy cell resistor Note This switch provides no protection in either position The cable connections can be handled safely only when the front panel cell disable switch is set to OFF Note that the Model 273A is controlled even when the cell isn t ON that is having the cell OFF does not cause an overload condition It might be noted that in the context of this discussion Cell ON and Cell OFF refer to the path from the Control Amplifier output to the Counter Electrode cable lead The red indicator does not respond to the status of the actual counter electrode connection That connection could be secure or faulty and it would have no effect on the red indicator which responds only to the Cell ON switch the CELL ENABLE switch and governing software However if the Cell is ON and there is no connection to the counter electrode the effect will be the same as if the cell had infinite resistance and an E OVERLOAD will occur 2 5 Defects and Abnormal Stresses Whenever it is likely that the protection provided by the connection to earth ground has been impaired do not use the instrument and secure it so others cannot use it
114. the value already in force When a setup parameter is displayed it can be changed by pressing the Setup Up Arrow key 1 which increases a parameter s value or the Setup Down Arrow key which decreases it It is not necessary to press the ENTER key to implement changes made with the arrow keys This technique is recommended for making small value changes These keys can also be used to change parameter values during an actual scan see discussion of 1 and i keys Note Take care not to confuse the 1 and keys with the CURRENT RANGE t t and 1 keys Note that the Model 273A does NOT apply a linear scan but rather a staircase scan However as long as the individual steps are very small relative to the range scanned linear scan theory will apply to a close approximation The nominal step size is the Rate 250 or 250 uV whichever is larger Note Under remote control via the rear panel GPIB or RS 232C port steps as small as 25 UV MR 1 or 2 5 uV MR 0 can be attained as explained in the Model 273A Remote Programming Command Handbook Example Given a scan rate of 1 V s the step size will be 4 mV i e 1000 250 4 Each Setup key is discussed in the following paragraphs 1 E I 1 2 and 3 These keys are used to specify the potential current applied at each of three stages in a scan or pulse sequence Potential is the controlled parameter in Potentiostat mode operation while current is controlled in Galvanostat
115. two indicators are located between the Scan Status and Alphanumeric Displays The OVERLOAD indicator lights if the cell current exceeds two times the selected Current Range Because it is impossible to reach currents of 2 A this lamp cannot light when the current range is 1 A However currents greater than 1 A will cause the E OVERLOAD indicator to light The E OVERLOAD indicator lights if the control amplifier output is at its limit gt 1A or Econtroi gt 100 V and the control loop is not controlling the cell potential or current This can happen in either Potentiostatic or Galvanostatic operation and normally indicates either a cell setup problem or an extremely high resistance solution Whenever E OVERLOAD lights the problem must be located and corrected before valid measurements can be made A common cause in potentiostatic operation is a disconnected reference electrode Note that this can cause damage to the working electrode if it occurs 5 2 3 Scan Status Display The Scan Status Display located at the upper left of the front panel consists of a symbolized scan waveform divided into sections marked by LED s light emitting diodes that correspond to the different stages of a scan As a scan progresses the LED corresponding to the scan stage in progress lights informing the user of the scan s status at a glance There are seven LED s on the Scan Status Display waveform A brief discussion of each follows 1 E I 1 When a scan
116. ve stressing of the front panel Appendix B provides instructions for rackmounting 3 1 12 Battery Backup A battery powered parameter backup system is provided This system assures that all parameters retain the values in effect at the end of the previous operating session In other words shutting the Model 273A off does not cause the default values to be restored They can however be restored by reinitializing the system via FUNCTION 10 The use of FUNCTION 10 is described in Section 5 2 4 Another way of restoring the default parameters is to press and hold in the LOCAL key as the Model 273A is being powered up The LOCAL key must be held in until the message SYSTEM REINITIALIZED appears on the front panel display 3 1 13 Front Panel Connectors 1 EXT INPUT 10 V analog input Potential applied is summed with that set at front panel or applied via digital interface Input impedance 100 kQ Model 273A Potentiostat Galvanostat User s Manual 2 E MONITOR 10 V analog output with output impedance of 1 kQ This is the potential of the working electrode with respect to the reference electrode IR compensation if active will affect the E MONITOR output level This same output is provided at the rear panel RECORDER INTERFACE connector MONITOR I E Converter Output 1 V for full scale current 2 V maximum Output impedance 1kQ OUTPUT Analog output that tracks current linear or log or charge coulombs Output impedance
117. ver when operated near particularly sensitive equipment interference emanating from this apparatus could be a problem Should this be the case steps can be taken to minimize that interference A discussion of the recommended steps follows 8 Model 273A Potentiostat Galvanostat User s Manual Interference below about 10 MHz is most likely to be caused by radio frequency currents flowing in the input and output cables in the digital interface cables or in the power line cord The use of coaxial cables in making the analog signal input output connection will usually prevent these lines from becoming a source of below 10 MHz radio frequency interference Two approaches are suggested for reducing interference that has its source in the digital interface cables The first is simply to shield these cables The second is to provide a heavy ground connection between the grounds of all equipment sharing the interface bus This is accomplished by strapping the chassis together with a metal braided or solid strap A solid strap does a better job but is more clumsy Copper aluminum or brass are the recommended materials Because the Model 273A has an internal low pass filter connected to the power line the ac line cord is unlikely to be a source of radio frequency interference If the internal filter seems to be inadequate try decoupling the power line with an external filter At frequencies below 100 kHz an external isolation transformer could be helpfu
118. was nee teste RE bebe Sees EER RE RE DEES REDE EE RE RE EE DERE SESE DE ES 18 32 7 Integrati n awison eSee beens BEE eRe eee se EERE SESE EE DEDEDE EE EE EERE EERE SEED ERE ES 18 3 2 9 Analog to Digital ARE bi bande eee ee See hee bees EE RE Se ee EE hehe EE EE bees SE RE Re 18 3 2 9 OUTPUT and AUX DIGITAL Connector 18 iii 3 2 10 273A 92 Electrochemical Impedance Interface Option 19 4 INITIAL CHECKS EE EE A E RR a 21 AT reeld ee 110 AE ER RR ER RR ER RR EE Ad 21 42 Required EQUIPMENT sets ta 21 ks SOUPS EA AE EE EE EE EE EI Ie 21 44 Procedur iese ese EE EE EE DE EE EE EE EE EE EE EE Ee EE Ee Ee EE eg SE ei 22 5 ORERATING INSTRUCTIONS pawa se Se Gee Ge E AA Ee SE E eg ge ei 25 ER Lee A 25 E 25 5 2 1 Alphanumeric Display 25 5 2 2 Overload and E Overload cuicos EE ee ra EG ST OE Eg ee ets 27 52 3 Scan Status DISPLAY outra EE RE RR EA ERA EE RE Ger ee Re ee Gag 27 5 24 SCAN SETUP Group ese bed es se Ge en ee ee aa er OE Rg ee ede 28 5 2 5 INTEREAGE GIOUPD iet re Ee Re id 35 5 2 6GONTROL Group aaa ie ee SE aa ee a a aa ede 36 5 2 7 MODEGIQUp ML OE EE ER EE IN 38 ode N EE a a tia 38 92 95 INPUT GROUP rose ee Re RE Re AR RE ge 39 5 2 10 FILTER Group Ene se es es ee er eg as 40 5 2 11 IR COMPENSATION Group ii Ee SS Ee ee 40 52412 E Vel EE ahat 46 52 13 CURRENT RANGE GrouP iis esse es We ee REE 46 5214 OUTPUT GOUE ER ee Ba a Gr don OE RE Ee er eN 47 Da Real Panel se ie ae GEENEEN GE Ge Ge Ge GE G
119. xecuted command The nature of the error can be determined by evaluating the ERR command response LOCAL This key returns the Model 273A from GPIB control to front panel control See Appendices A and B of the Model 273A Remote Programming Command Handbook for a discussion of GPIB Communications Considerations It is effective only if the GPIB LOCAL LOCKOUT message has not been applied Also as long as REN continues to be asserted applying the Model 273A s LISTEN address will immediately restore GPIB control Note that this key does not affect control of the Model 273A via the RS 232C Interface which is always active If the LOCAL key is pressed while executing a multiple remote command an error will occur because there will be a remote local violation The host computer can avoid this possibility by sending LOCAL LOCKOUT a GPIB message which disables the effect of the LOCAL key Chapter 5 Operating Instructions 35 36 5 2 6 CONTROL Group 1 SCANNING This indicator is off at power up and on during each active scan At powerup the E l APPLIED indicator is lighted indicating that the 273A is ready to apply the previously speed E I APPLIED level It won t actually be applied however unless both the CELL switch and the CELL ENABLE switch are ON If a scan is initiated by pressing START the E I APPLIED indicator goes out and the SCANNING indicator lights signifying that a scan is underway The progress of the scan can be mon
120. y or at certain affiliate facilities Contact the factory service department or the affiliate in your area if service is required There are no operator serviceable parts inside Refer servicing to qualified personnel Chapter 1 Introduction 3 Model 273A Potentiostat Galvanostat User s Manual 2 SAFETY CONSIDERATIONS 2 1 Introduction The apparatus to which this instruction manual applies has been supplied in a safe condition This manual contains some information and warnings that have to be followed by the user to ensure safe operation and to retain the apparatus in a safe condition The described apparatus has been designed for indoor use 2 2 Safety Mechanism As defined in EEC Publication 348 Safety Requirements for Electronic Measuring Apparatus the Model 273A is Class apparatus that is apparatus that depends on connection to a protective conductor to earth ground for equipment and operator safety Before any other connection is made to the apparatus the protective earth terminal must be connected to a protective conductor The protective connection is made via the earth ground prong of the Model 273A s power cord plug This plug shall only be inserted into a socket outlet provided with the required earth ground contact The protective action must not be negated by the use of an extension cord without a protective conductor by use of an adapter that doesn t maintain earth ground continuity or by any other means The powe

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