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7025 User Manual

1. LHM 318VO NO 1431 5 92 133HS 31495 5 3 1944 HO O3NNOO OVA 0 2 HOA MOTS 4 S SGSc LOOg8 a Mice NOLLVH3dO OVA SEL MOTS div 01 ISNA WALSAS OVA ON 4054 3215 NDIS30 Nu9 2 NOllVH3dO OVA d V9 3sndualvaH z 1 3SIMH3HIO SS3 TNf 9 901 NOLLWINSNI 9 H LIM H3ddOO 15 DMV 91 NMOHS S3UIM TIV INVHOVIG DNIYIM 93202 S31ON 96 91 ONO NMVHG 0091 6 108 OIHLLN3IOS 3iva VAOHddV 9216 20078 HVH NVOIH3IAV ON LOVHINOO H LH Qr Ner U UL del NOLLVENDIINOD OVA 0 c ya LV3H RA inoino 7 0 199 41120000 LYVd 13S 80d 110100 poe ees unu 31dNOOOWYSHL 15UO BEREM AV IdSIa A SEHE 9082 010 A AHO 1HM ALLHM 81 OHO LHM 9 AV IdSIG son T ir as prx NI Ov ono TOO E ono 81 M18 D80 1HM LS 5UO IHM s3sn3 HOLIMS W3LSAS zm H3MOd m Zr 8L 8L T3A 1HM ce IVNOILdO
2. 33 912 4 EMOS ue e GE Nu Eun b AAA AO ESE HER 33 9 13 IEEE 4898 Parameters lt lt lt 4 65 amp dS am Se eS Bod So d ee 33 9 13 1 IEEE 488 Address 33 9 14 Calibration Parameters 34 OA CTO da wht del Esti Ge es o A 34 Ota BOI BO uci deos eode run d pA ee E 34 IES PANGE ss Gs Gh 34 10 Digital Communication Interface 35 10 1 Serial 5 35 DAT WING DA AAA RAR A A 35 AS d ORE Feta hk 35 4 aos Rede Area eu cede 35 10 1 2 2 Sampe Pernod xs etude Rx be 5 Reed Bk Por mx 36 10423 Duplex Mode de 36 Ora MENS ce vera E 36 10 175 Sena ODeralloH ens ed 36 10 2 IEEE 488 Communication optional 36 da E Bae E Yos bb E LESE Ue Hom d E bs 36 10 2 1 1 IEEE 488 Interface Address 36 1022 JEEE 499 ODSG
3. 20 TWISCOSIDES ux de Ear he A 20 Stes i as Renee sek ow mo 20 8 1 4 Thermal Conductivity 20 9 19 PAGKIMANMEXOANSION aa EU ure SD De im ey 20 ES VI 9 145 Elecilical HesliSllVIDy ss I E A de REP 20 8 1 7 Fluid Lifetime 2 21 Bae Gale OAR ERE EEE 21 IG OS 21 8 1 10 Commonly Used Fluids 21 Oe IMCD va a ee Tee 21 81 102 Ethylene GIVCOl x i dew mE Shs amp Gow BS BAS e del qx 21 e la Mat ee 21 Silicone Oil 22 9 1 11 Fluid Characteristics Charts 2 Ade A ak doe a oue ew 22 8 1 11 1 Limitations and Disclaimer 23 Bate About ilie redria Seis o aded v es aS eund 24 a 24 24 che 24 8 5 Temperature Controller 24 8 6 HelrigerallOD 2425 8 d eo
4. 10 2 9 Waly dc a hae So do ee do dos duh de 10 Safety Guidelines 12 13 41 UNPACKING ar A a DEOR 13 AZ SOUND 13 Bea A 13 44 Setting the Temperature 13 MARIE 15 S L BbhVIrOnmell ax ana dew Ws Spe EA AAA 15 9 2 DIVOULL PENO x x ende ae eS 15 5 3 Bath Preparation and Filing 15 DA WOODS sca ok qose Bae SS a eub Br eh OS e b ur a 15 DO FONO o ra 15 BaN USE tae tag tag es 16 oO TL s uod e E ead 16 6 2 Comparison Calibration 16 6 3 Calibration of Multiple Probes 17 Paris and CONOS saaa a a 18 k x Ae Ar 18 fe bid Oe de nm a ed 18 To tibl dr Beech ace oot Eod A dicar Dowd 19 General Operation 20 8 1 Heat Transfer Fluid 20 8 1 1 Temperature Range
5. Accept new set point value 28 Manual Rev 722602 9 3 3 Set point Vernier The set point value can be set with a resolution of 0 01 C The user may want to adjust the set point slightly to achieve a more precise bath temperature The set point vernier allows one to adjust the tem perature below or above the set point by a small amount with very high resolution Each of the 8 stored set points has an associated vernier setting The ver nier is accessed from the set point by pressing SET The vernier setting is displayed as a 6 digit number with five digits after the decimal point This is a tem perature offset in degrees of the selected units C or Current vernier value in C To adjust the vernier press UP or DOWN Unlike most functions the vernier setting has immediate ef fect as the vernier is adjusted SET need not be pressed This allows one to continually adjust the bath temperature with the vernier as it is displayed Increment display New vernier setting Next press EXIT to return to the temperature display or SET to access the temperature scale units selec tion Access scale units 9 4 Temperature Scale Units The temperature scale units of the controller may be set by the user to degrees Celsius C or Fahrenheit F The units will be used in displaying the bath temperature set point vernier proportional band and cut out set point The temperature sc
6. usc cu ideo XE Redde 46 Wiring Diagram with I O 47 1 Introduction The Hart Scientific Model 7025 is a bench top con stant temperature bath useful in temperature calibra tion and other applications requiring stable temperatures An innovative state of the art solid state temperature controller has been incorporated which maintains the bath temperature with extreme stability The temperature controller uses a microcontroller to execute the many operating functions HART SCIENTIFIC Figure 1 7025 Calibration Bath Model 7025 Introduction User interface is provided by the 8 digit LED display and four key switches Digital remote communications is optionally available with an RS 232 or IEEE 488 interface The 7025 bath was designed to be compact and low cost without compromising performance The 7025 bath operates over a wide temperature range from 20 C to 110 C The refrigeration permits sub ambi ent temperature control 7025 High Precision Bath Manual Rev 722602 9 Specifications and Environmental Conditions 2 Specifications and Environmental Conditions 2 1 Specifications See l ble T 2 2 Environmental Conditions Although the instrument has been designed for opti mum durability and trouble free operation it must be handled with care The instrument should not be operated in an excessively dusty or dirty environment Maintenance and cleaning
7. munication equipment by pressing UP or DOWN and then SET 10 2 2 488 Operation Commands may now be sent via the IEEE 488 inter face to read or set the temperature or access other controller functions All commands are ASCII charac ter strings and are terminated with a carriage return CR ASCII 13 Interface commands are listed below 10 3 Interface Commands The various commands for accessing the bath con troller functions via the digital interfaces are listed in this section See 18012 4 THese commands are used with both the RS 232 serial interface and the IEEE 488 GPIB interface In either case the commands are Hart Scientific Table 4 Interface Command Summary Digital Communication Interface Command Command Returned Acceptable Command Description Format Example Returned Example Values Display Temperature Read current set point s etpoint S set 9999 99 C or set 150 00 C Set current set point to n s etpoint n s 450 Instrument Range Read vernier v ernier V v 9 99999 v 0 00000 Set vernier to n v ernier n v 00001 Depends on Configuration Read temperature t emperature t t 9999 99 C or F t 55 69 C Read temperature units u nits u x u c Set temperature units u nits c f Set temperature units to u nits c u C Celsius Set temperature units to u nits f u f F
8. 0 1 8 9 85 0 810 Q O C 0 6 0 0005 O 20 0 0014 25 0 66 0C 0 792 20 0 45 20 Water 0 C fr 95 b 16 257 1 00 1 00 0 0014 0 0002 25 C 0 40 75 C Ethylene 935 C fr 110 C b 700 1 05 0 80 0 0 001 Glycol 5096 2 50 5020 0 7 100 C Mineral Oil 40 C v 190 C fl 190C 15 75 0 87 25 0 48 25 0 00025 6 0 0007 50 5 Q9 25 5 125 C 0 84075C 0 53 75 25 C 0 81 125 C 0 57 125 C Dow Corning 40 C v 133 C fl cc 13390 5 25T 0 92 25 C 0 4 0 00028 0 00105 1000 25 C 200 5 25 C 10 150 C Silicone Oil Dow Corning 35 C v 16592 fl cc 165 10 25T 0 934 0 250 0 43 40 0 00032 0 00108 1000 25 C 200 10 3 135 C 0 45 100 C 25 C 50 150 C 5012 0 482 200 C Dow Corning 7 C v 230 fl cc 2307 20 25T 0 949 25 C 0 3700 40 C 0 00034 O 0 00107 1000 25 C 200 20 0 393 100 C 25 C 50 150 C 5013 0 420 200 C Dow Corning 25 C v 280 fl cc 280 C 20 25 0 96 25 C 0 4 0 00037 0 00104 1000 25 C 200 50 25 C 50 150 C Silicone Oil Dow Corning 70 v 232 fl cc 232 C 50 Q 70 C 1 07 25T 0 358 40 0 00035 O 0 00075 100 25 550 300 C fl oc 10 104 C 0 386 100 C 25 C 1 150 C 5016 0 433 200 C Dow Corning 80 C v 302 C fl oc 302 C 50 80 1 11 25 C 0 363 40C 0 00035 0 00077 100 25 710 7 204 0 454 100 25 1 150 C 5017 0 505 200 C Dow Corning 66 C v
9. 182 600 81 NYS 88v 33Hl X18 13A 1HM 887 3991 Ir vr XT8 OIWIHM NYOMJA ud S08c 010 010 i W W Y IVLIDIO DOWNY IVNOI LdO A 30V343LNI 1935 fa AV I3H AWD 1 bs y Lo OIA SITE N o e re no Do e OMV 81 ME OINIHM evac 100 L 9 v OMV 81 OIA e io io 81 H ue E gt V i HOSS3HdWOO 3 j Pp NHO 8 O0lld J 47 N O O N N N gt gt Q S 5 Q D LO 5 o N E 3 O D
10. 44 14 1 5 The Controller Controls Or Attempts To Control At An Inaccurate Temperature 44 14 1 6 The Controller Shows That The Output Power is Steady But The Process Temperature is Unstable 44 14 1 7 The Controller Alternately Heats For A While then Cools 44 14 1 8 The Controller Erratically Heats Then Cools Control Unstable 44 Vii 14 1 9 The Bath Does Not Achieve Low Temperatures 44 14 2 Wiring Diagrams Figure 1 Table 1 Figure 2 Figure 3 Table 2 Figure 4 Table 3 Figure 5 Figure 6 Table 4 Table 4 Figure 7 Figure 8 Figure 9 vill NUM ety ND NE B CHOR aap Ru puc ue wed 46 Figures and Tables 7025 Calibration Bath 9 ODSGHICSHOLlS q s ages 3 oS Re 10 Front Panel Features 18 Chart showing usable range of various fluids 22 Table oT Bath pb RON uo Redi ur 23 Controller Operation Flowchart 27 Proportional Band Fluid Table 30 Bath temperature fluctuation at various proportional band settings 30 Serial Communications Cable Wiring 35 Interface Command Summary 37 Interface Commands continued 38 Calibration Example 40 VILI
11. 81 NI OV 9 LUN 8L OIA 8L 18 9HO 1HM 81 119 040 1HM NH9 13A NHO T3JA 8L 81 IHA LHM 81 NHO 31713 709 010 Sasnd WALSAS qHs 5 8L OIA LHM 8 NYS ma 8L CJ MNIg TI LIHM x18 LHM je p fs 9 me 9 on ca A X18 LHM LO ma n Quero 318VO NO 1331 5 92 lOHINOO Figure 8 Wiring Diagram Hart Scientific Manual Hev 722602 46 Troubleshooting
12. In this case the user may set the interface address within the IEEE 488 parameter menu This menu does not appear on baths not fitted with the interface The menu is indicated by IEEE i 488 parameters menu Press SET to enter the menu IEEE 488 Address The IEEE 488 interface must be configured to use the same address as the external communicating device The address is indicated by IEEE 488 interface address Press SET to access the address setting Manual Hev 722602 33 Controller Operation Current IEEE 488 interface ad dress Adjust the value with UP or DOWN and then use SET to set the address to the displayed value ps jns pm A E 9 14 Calibration Parameters The operator of the bath controller has access to a number of the bath calibration constants namely CTO BO BG H and L These values are set at the factory and must not be altered The correct values are im portant to the accuracy and proper and safe operation of the bath Access to these parameters is available to the user only so that in the event that the controller s memory fails the user may restore these values to the factory settings The user should have a list of these constants and their settings with the manual DO NOT change the values of the bath calibra tion constants from the factory set values The correct setting of these parameters is important to the safety and proper operation of the bath The calibration
13. Rev 722602 37 Digital Communication Interface Interface Commands continued Command Command Returned Acceptable Command Description Format Example Returned Example Values Calibration Menu Read BO calibration parameter 60 9 b0 0 Set BO calibration parameter to n b0 n b0 0 999 9 to 999 9 Read BG calibration parameter bg 999 99 bg 156 25 Set BG calibration parameter to n bg n bg 156 25 999 9 to 999 9 Read low set point limit value tl 999 tl 80 Set low set point limit to n tll ow n tl 80 999 9 to 999 9 Read high set point limit value th igh th th 999 th 205 Set high set point limit to n th igh n th 205 999 9 to 999 9 Miscellaneous not on menus Read firmware version number ver sion ver ver 9999 9 99 7025 3 56 Read structure of all commands h elp h list of commands Set Refrigeration f2 1 0 0 or 1 Set Refrigeration to on f2 n f2 1 Set Refrigeration to off f2 n f2 0 Legend Optional Command data Returns either information n Numeric data supplied by user 9 Numeric data returned to user x Character data returned to user Note When DUPLEX is set to FULL and a command is sent to READ the command is returned followed by a carriage return and linefeed Then the value is returned as indicated in the RETURNED column terminated with a carriage return character The inter face makes no distinction between up
14. parameters menu is indicated by 34 Manual Rev 722602 CAL Calibration parameters menu Press SET five times to enter the menu 9 14 1 CTO Parameter CTO sets the calibration of the over tem perature cut out This is not adjustable by software but is adjusted with an internal potentiometer For the 7025 baths this parameter should read between 110 and 130 9 142 BO and BG These parameters calibrate the accuracy of the bath set point These are programmed at the factory when the bath is calibrated Do not alter the value of these parameters If the user desires to calibrate the bath for improved accuracy then calibrate R and ALPHA according to the procedure given in TT 9 14 3 HandL These parameters set the upper and lower set point limits of the bath DO NOT change the values of these parameters from the factory set values To do so may present danger of the bath exceeding its temperature range causing damage or fire Hart Scientific Digital Communication Interface 10 Digital Communication Interface If supplied with the option the 7025 bath is capable of communicating with and being controlled by other equipment through the digital interface Two types of digital interface are available the RS 232 serial interface and the IEEE 488 GPIB interface With a digital interface the bath may be connected to a computer or other equipment This allows the user to set the bath temperature monitor th
15. played again 14 Manual Rev 722602 Return to the temperature display Bath temperature display The bath heats or cools until it reaches the new set point temperature Turn off the cooling to reach and control at higher temperatures When setting the set point temperature be careful not to exceed the temperature limit of the bath fluid The over temperature cut out should be correctly set for added safety See Sefiion 9 8 To obtain optimum control stability adjust the propor tional band as discussed in Seftion 9 7 Hart Scientific 5 Installation CAUTION READ SECTION 6 ENTITLED BATH USE before placing the bath in service Incorrect handling can damage the bath and void the warranty 5 1 Bath Environment The Model 7025 Bath is a precision instrument which should be located in an appropriate environment The location should be free of drafts extreme tempera tures and temperature changes dirt etc The surface where the bath is placed must be level Allow plenty of space around the bath for air circulation The top surface of the bath may become hot at high temperatures Beware of the danger of accidental fluid spills A fume hood should be used to remove any vapors given off by hot bath fluid 5 2 Dry out Period Before initial use after transport and any time the instrument has not been energized for more than 10 days the bath will need to be energized for a dry out period of 1 2 h
16. point The bath temperature can be set to any value within the range and with resolution as given in the specifi cations The temperature range of the particular fluid used in the bath must be known by the operator and the bath should only be operated well below the upper temperature limit of the liquid In addition the cut out temperature should also be set below the upper limit of the fluid oetting the bath temperature involves three steps 1 select the set point memory 2 adjust the set point value and 3 adjust the vernier if desired 9 3 1 Programmable Set points The controller stores 8 set point temperatures in memory The set points can be quickly recalled to conveniently set the bath to a previously programmed temperature set point To set the bath temperature one must first select the set point memory This function is accessed from the temperature display function by pressing SET The number of the set point memory currently being used Hart Scientific Controller Operation Display Temperature SET EXIT Set Scale C F Adj Cutout Reset Mode SET EXIT SET EXIT Secondary Functions SET EXIT Display Power SET SET SET Configuration Menu SET IEEE 488 Interface Serial Interface Calibration Menu Adjust BAUD Rate SET EXIT Adj Device Address SET EXIT Adjust CTO SET EXIT IE
17. the probe s to be calibrated as closely grouped as possible in the working area of the bath Bath stability is maximized when the bath working area is kept covered In preparing to use the bath for calibration start by e Placing the reference probe in the bath work ing area Hart Scientific Bath Use e Placing the probe to be calibrated the UUT in the bath working area as close as feasibly 6 3 _ Calibration of Multiple possible to the reference probe Model 7025 Probes Fully loading the bath with probes increases the time required for the temperature to stabilize after inserting the probes Using the reference probe as the guide be sure that the temperature has stabilized before starting the calibration Manual Rev 722602 17 Parts and Controls 7 Parts and Controls 7 1 Front Panel The following controls and indicators are present on the controller front panel see Figure 2 belpw 1 the digital LED display 2 the control buttons 3 the bath on off power switch 4 the control indicator light and 5 the cooling on off switch 1 The digital display is an important part of the temperature controller It displays the set point temperature and bath temperature as well as the various other bath functions settings and con stants The display shows temperatures according to the selected scale units C or F 2 The control buttons SET DOWN UP and EXIT are used to set the bath temperatur
18. which ignition may occur The point shown may be either the open or closed cup flash point Refer to the flash point discussion in 8 18 Boiling Point At or near the boiling point of the fluid the temperature stability is difficult to maintain Fum ing or evaporation is excessive Large amounts of heater power may be required because of the heat of vaporization Decomposition The temperature may reach a point at which decomposition of the fluid begins Further increasing the temperature may accelerate decompo sition to the point of danger or impracticality 8 2 Stirring Stirring of the bath fluid is very important for stable temperature control The fluid must be mixed well for good temperature uniformity and fast controller re 24 Manual Rev 722602 sponse The stirrer is precisely adjusted for optimum performance 8 3 Power Power to the bath is provided by an AC mains supply of 115 10 60 Hz 8 A 230 10 50 Hz 4 A optional Power to the bath passes through a filter to prevent switching spikes from being transmit ted to other equipment To turn on the bath switch the control panel power switch to the ON position The stirring motor will turn on the LED display will begin to show the bath temperature and the heater will turn on or off until the bath temperature reaches the programmed set point When powered on the control panel display will briefly show a four digit number This num
19. 0 The sample period is indicated by Serial sample period parameter Press SET to choose to set the sample period The current sample period value will be displayed Current sample period sec onds Adjust the value with UP or DOWN and then use SET to set the sample rate to the displayed value New sample period 9 12 3 Duplex Mode The next parameter is the duplex mode The duplex mode may be set to full duplex or half duplex With full duplex any commands received by the bath via the serial interface will be immediately echoed or trans mitted back to the device of origin With half duplex the commands will be executed but not echoed The duplex mode parameter is indicated by Serial duplex mode parameter Press SET to access the mode setting Model 7025 9 13 1 Controller Operation Current duplex mode setting The mode may be changed using or DOWN and pressing SET New duplex mode setting 9 12 4 Linefeed The final parameter in the serial interface menu is the linefeed mode This parameter enables on or dis ables off transmission of a linefeed character LF ASCII 10 after transmission of any carriage return The linefeed parameter is indicated by LF Serial linefeed parameter The mode may be changed using UP or DOWN and pressing SET New linefeed setting 9 13 IEEE 488 Parameters Baths may optionally be fitted with an IEEE 488 GPIB interface
20. 315 C fl oc 315 C 50 66 C 0 96 25T 0 34 100 C 0 0003 0 00095 100 25 210 H 14 204 C 1 150 C Silicone Oil Heat Transfer 145 C fr 530 C NONE 34 150 C 2 0 150 C 0 33 0 0014 0 00041 1 7 Q cm salt 6 5 9 300 1 9 9 300 5001 24 500C 1 7 500 Limiting Factors b boiling point e high evaporation fl flash point fr freeze point v viscosity Flash point test low water solubility ice will form as a slush from condensation below freezing open closed 81111 Limitations and Disclaimer The information given in this manual regarding fluids is intended only to be used as a general guide in choosing a fluid Though every effort has been made to provide correct information we cannot guarantee accuracy of data or assure suitablility of a fluid for a particular application Specifications may change and sources sometimes offer differing information Hart ocientific cannot be liable for any personal injury or damage to equipment product or facilities resulting from the use of these fluids The user of the bath is Model 7025 responsible for collecting correct information exercis ing proper judgment and insuring safe operation Operating near the limits of certain properties such as the flash point or viscosity can compromise safety or performance Your company s safety policies regard ing flash points toxicity and such issues must be considered You are re
21. Bath Hart Scientific Model 7025 e The control probe provides the temperature feedback signal to the controller allowing the controller to maintain a constant temperature The control probe is a precision platinum resis tance thermometer PRT It is delicate and must be handled carefully The probe is placed in the small hole in the top of the bath so that the probe tip is fully immersed in the bath fluid The stirring motor is mounted on the bath tank lid It drives the stirring propeller to provide mixing of the bath fluid Proper mixing of the fluid is important for good constant tempera ture stability On the bath lid is a large access hole This is used for filling and emptying the bath with fluids and placement of thermometers and devices Parts and Controls into the bath When possible the access hole should be covered An access hole cover should be used to cover the access opening in the top of the bath This improves bath temperature stability prevents excess fluid evaporation or fumes and in creases safety with hot fluid The user may drill or cut holes in the cover to accommodate the instruments to be calibrated or immersed in the bath Spare covers are available from Hart Scientific 7 3 Back Panel On the back of the bath are the system fuses and the non removable power cord Manual Rev 722602 19 General Operation 8 General Operation 8 1 Heat Transfer Fluid Many fluids will work with 7025 b
22. E The sample period is the time period in seconds between temperature measurements transmitted from the serial interface If the sample rate is set to 5 for instance then the bath will transmit the current measurement over the serial interface approximately every five seconds The auto matic sampling is disabled with a sample period of O Press SET to choose to set the sample period Adjust the period with UP or DOWN and then use SET to set the sample rate to the displayed value 10 1 2 3 Duplex Mode The next parameter is the duplex mode indicated with gUPL The duplex mode may be set to half duplex HALF or full duplex FULL With full duplex any commands received by the bath via the serial inter face will be immediately echoed or transmitted back to the device of origin With half duplex the commands will be executed but not echoed The default setting is full duplex The mode may be changed using UP or DOWN and pressing SET 10 1 2 4 Linefeed The final parameter in the serial interface menu is the linefeed mode This parameter enables 8 or disables transmission of a linefeed character LF ASCII 10 after transmission of any carriage re turn The default setting is with linefeed on The mode may be changed using UP or DOWN and pressing SET 10 1 3 Serial Operation Once the cable has been attached and the interface set up properly the controller will immediately begin tra
23. EE 488 Option Installed Adj Sample Period SET EXIT Adjust BO SET EXIT DO NOT CHANGE THESE VALUES SEE MANUAL Adj Duplex Mode SET EXIT Adjust BG SET EXIT Linefeed SET EXIT Adjust H SET EXIT Interface Option Installed Adjust L SET EXIT Figure 4 Controller Operation Flowchart Model 7025 Manual Hev 722602 27 Controller Operation is shown at the left on the display followed by the current set point value Bath temperature in degrees Celsius Access set point memory Set point memory 1 25 0 C currently used change the set point memory press UP or DOWN Increment memory Pu MUN 400 Press to accept the new selection and access the set point value Accept selected set point memory 9 3 2 Set point Value The set point value may be adjusted after selecting the set point memory and pressing SET The set point value is displayed with the units C or F at the left Set point 4 value in C If the set point value need not be changed then press EXIT to resume displaying the bath temperature Press UP or DOWN to adjust the set point value Increment display New set point value When the desired set point value is reached press SET to accept the new value and access the set point vernier If EXIT is pressed instead then any changes made to the set point will be ignored
24. EXIT button 9 2 Reset Cut out If the over temperature cut out has been triggered then the temperature display will alternately flash Indicates cut out condition The message will continue to flash until the tempera ture is reduced and the cut out is reset The cut out has two modes automatic reset and manual reset The mode determines how the cut out Is reset which allows the bath to heat up again When in automatic mode the cut out will reset itself as soon as the temperature is lowered below the cut out set point With manual reset mode the cut out must be reset by the operator after the temperature falls below the set point When the cut out is active and the cut out mode is set to manual reset then the display will flash cut out 26 Manual Rev 722602 until the user resets the cut out To access the reset cut out function press the SET button Access cut out reset function The display will indicate the reset function Cut out reset function Press SET once more to reset the cut out Heset cut out This will also switch the display to the set temperature function To return to displaying the temperature press the EXIT button If the cut out is still in the over tem perature fault condition the display will continue to flash cut out The bath temperature must drop a few degrees below the cut out set point before the cut out can be reset 9 3 Temperature Set
25. Instruction TZ point see the chart on the bath Model 7025 Manual Hev 722602 45 Troubleshooting iagrams D iring 14 2 W vr Ad 133HS 31495 5 3 1944 9552 1009 7879 a H3HNION3 ON DMG NOS 3258 NOIS3G m AN D Es 96 91 ONO NMVHG 0091 26 108 2IJLLN3IOS 9216 60078 NVOIH3INV 41120000 LYVd LAS 89d Q3HOLVIN 89d AV1dSIG 9082 010 or ir S08c 010 99 IWLISIG 3INODONE3HL X 1HM A TAA LHM vr OVIEL YOLOANNOO 3oN3u3d3u NOILVH3dO OVA 0 Z 85 dV S 1HM S NOIIVH3dO OVA SIE HOW 8S 0L 3Sfd WALSAS ya 5 OWA 0EZ HOW dY 2 No y oe NOLIVE3dO OYA SLL dAY 9 ISNA Z 8 1 3SIME3HLO SS3 TNn 9 901 GALVY NOLIVINSNI H3ddOO 15 DMV 91 NMOHS S3HIM TIV SALON X IB AHO LHM 59515 H3lV3H LNOLND 9 YUU 6 8 2 NOLLVENDIANOO OVA 068 t H3lV3H o 7 9 9 v NOILVHNDISNOO 81940 OVA SLL H3lV3H 8
26. Model 7025 Calibration Bath User Manual HART SCIENTIFIC Manual Hev 722602 Copyright 1996 rights reserved Hart Scientific 799 E Utah Valley Drive American Fork Utah 84003 9775 Telephone 801 763 1600 Fax 801 763 1010 Internet http www hartscientific com WARNING To ensure the safety of operating personnel and to avoid damage to this unit DO NOT operate this unit without a properly grounded properly polarized power cord DO NOT connect this unit to a non grounded non polarized outlet DO use ground fault interrupt device WARNING EXTREMELY COLD TEMPERATURES PRESENT in this equipment FREEZER BURNS AND FROSTBITE may result if personnel fail to observe safety precautions WARNING HIGH TEMPERATURES PRESENT in this equipment FIRES AND SEVERE BURNS may result if personnel fail to observe safety precautions WARNING Fluids used in this bath may produce NOXIOUS OR TOXIC FUMES under certain circumstances Consult the fluid manufacturers MSDS Material Safety Data Sheet PROPER VENTILATION AND SAFETY PRECAUTIONS MUST BE OBSERVED WARNING CALIBRATION EQUIPMENT SHOULD ONLY BE USED BY TRAINED PERSONNEL Table of Contents Introduction 9 Specifications and Environmental Conditions 10 Zl 5 de ox un Be Reve a Pe 10 2 2 Environmental Conditions
27. Please read 5 trough 8 carefully before operating the bath 4 1 Unpacking Unpack the bath carefully and inspect it for any dam age that may have occurred during shipment If there is shipping damage notify the carrier immediately Verify that all components are present 7025 Bath Access Hole Cover Controller Probe Manual If you are missing any item please call Hart Scientific Customer Service at 801 763 1600 4 2 Set Up oet up of the bath requires careful unpacking and placement of the bath filling the bath with fluid and connecting power Consult Seftion 5 Tor detailed in structions for proper installation of the bath Be sure to place the bath in a safe clean and level location Fill the bath tank with an appropriate liquid For opera tion at moderate bath temperatures clean distilled water works well Carefully pour the fluid into the bath tank through the large rectangular access hole above the tank avoiding spilling any fluid The fluid must not exceed a height of 1 2 inch below the top of the tank Model 7025 Quick Start 4 3 Power Plug the bath power cord into a mains outlet of the proper voltage frequency and current capability Typi cally this will be 115 10 60 Hz 8 A 230 VAC 10 50 Hz 4 A optional Turn the bath on using the front panel POWER switch The bath will turn on and begin to heat or cool to reach the previously programmed temperature set
28. Set point Error The first step in the calibration procedure is to meas ure the temperature errors including sign at the two calibration temperatures First set the bath to the lower set point which we will call t Wait for the bath to reach the set point and allow 15 minutes to stabilize at that temperature Check the bath stability with the thermometer When both the bath and the thermome ter have stabilized measure the bath temperature with the thermometer and compute the temperature error err which is the actual bath temperature minus the Model 7025 set point temperature If for example the bath is set for a lower set point of t 0 C and the bath reaches a measured temperature of 0 3 C then the error is 0 3 C Next set the bath for the upper set point t and after stabilizing measure the bath temperature and com pute the error err For this example we will suppose the bath was set for 100 C and the thermometer measured 100 1 C giving an error of 0 1 C 11 3 Computing and ALPHA Before computing the new values for and ALPHA the current values must be known The values may be found by either accessing the probe calibration menu from the controller panel or by inquiring through the digital interface The user should keep a record of these values in case they may need to be restored in the future The new values and ALPHA are com puted by entering the old values for and ALPHA the calibra
29. about 0 5 C 8 6 Refrigeration Bath cooling below 45 C is provided by a compact refrigeration system The system utilizes the ozone safe R 404A refrigerant The refrigerant is metered through an automatic expansion valve to achieve bath temperatures as low as 20 C The evaporator and heater are sandwiched to the bottom of the tank This provides the precision control over heat gains and losses required for high stability Manual Hev 722602 25 Controller Operation 9 Controller Operation This chapter discusses in detail how to operate the bath temperature controller using the front control panel Using the front panel key switches and LED display the user may monitor the bath temperature set the temperature set point in degrees C or F moni tor the heater output power adjust the controller proportional band set the cut out set point and pro gram the probe calibration parameters operating pa rameters serial and IEEE 488 interface configuration and controller calibration parameters Operation is summarized in Figure 4 9 1 Bath Temperature The digital LED display on the front panel allows direct viewing of the actual bath temperature This tempera ture value is what is normally shown on the display The units C or F of the temperature value are dis played at the right For example Bath temperature in degrees Celsius The temperature display function may be accessed from any other function by pressing the
30. ahrenheit Secondary Menu Read proportional band setting pr op band pr pr 999 9 pr 15 9 Set proportional band to n pr op band n pr 8 83 Depends on Configuration Read cutout setting c utout C c 9999 x xxx 620 C in Set cutout setting c utout n r eset Set cutout to n degrees c utout n 500 Temperature Range Reset cutout now c utout r eset c r Read heater power po wer po po 9999 po 1 duty cycle Configuration Menu Probe Menu Read RO calibration parameter 0 999 999 r0 100 578 Set RO calibration parameter to n r O n r 100 324 98 0 to 104 9 Read ALPHA calibration parameter al pha al al 9 9999999 al 0 0038573 Set ALPHA calibration parameter to n al pha n 0 0038433 00370 to 00399 Operating Parameters Menu Read cutout mode cm ode cm cm xxxx cm AUTO Set cutout mode cm ode r eset a uto RESET or AUTO Set cutout to be reset manually Set cutout to be reset cm ode a uto cm a automatically Serial Interface Menu Read serial sample setting sa mple sa sa 9 sa 1 Set serial sampling setting to n sa mple n 0 0 to 4000 seconds Set serial duplex mode du plex f ull h alf FULL or HALF Set serial duplex mode to full du plex f ull du f Set serial duplex mode to half du plex h alf Set serial linefeed mode Iffeed zon of f ON or OFF Set serial linefeed mode to Ifleed on lf on Set serial linefeed mode to off lIf eed of f If of Model 7025 Manual
31. ale units selection is accessed after the vernier adjustment function by pressing SET From the temperature display function access the units selection by pressing SET 4 times Bath temperature Access set point memory Hart Scientific 8 00800 Vernier setting Access scale units selection T P ee Press SET to accept the new selection and resume displaying the bath temperature Set the new units and resume temperature display 9 5 Secondary Menu Functions which are used less often are accessed within the secondary menu The secondary menu is accessed by pressing SET and EXIT simultane ously and then releasing The first function in the secondary menu is the heater power display 9 6 Heater Power The temperature controller controls the temperature of the bath by pulsing the heater on and off The total power being applied to the heater is determined by the duty cycle or the ratio of heater on time to the pulse cycle time This value may be estimated by watching the red green control indicator light or read directly from the digital display By knowing the amount of heating the user can tell if the bath is heating up to the set point cooling down or controlling at a constant temperature Monitoring the percent heater power will Model 7025 Controller Operation let the user know how stable the bath temperature is With good control stability the percent heating p
32. an be replaced Contact Hart Scientific Customer Serv ice for assistance The probe is inserted into the probe hole at the top right side of the bath so that the tip of the probe is well immersed in the fluid 55 Power With the bath power switch off plug the bath into an AC mains outlet of the appropriate voltage frequency and current capacity Normally this will be 115 VAC 10 60 Hz 8 A 230 VAC 10 50 Hz 4 A optional Manual Rev 722602 15 Bath Use 6 BathUse READ BEFORE PLACING THE BATH IN SERVICE The information in this section is for general informa tion only It is not designed to be the basis for calibra tion laboratory procedures Each laboratory will need to write their own specific procedures 6 1 General Be sure to select the correct fluid for the temperature range of the calibration Bath fluids should be selected to operate safely with adequate thermal properties to meet the application requirements Also be aware that some fluids expand and could overflow the bath if not watched Refer to General Operation Seftion 8 for information specific to fluid selection and to the MSDS sheet specific to the fluid selected Generally baths are setto one temperature and used to calibrate probes only at that single temperature This means that the type of bath fluid does not have to change Additionally the bath can be left energized reducing the stress on the system The bath generates extrem
33. ath Choosing a fluid requires consideration of many important charac teristics of the fluid Among these are temperature range viscosity specific heat thermal conductivity thermal expansion electrical resistivity fluid lifetime Safety and cost 8 1 1 Temperature Range One of the most important characteristics to consider is the temperature range of the fluid Few fluids work well throughout the entire temperature range of the bath The temperature at which the bath is operated must always be within the safe and useful temperature range of the fluid used The lower temperature range of the fluid is determined either by the freeze point of the fluid or the temperature at which the viscosity becomes too great The upper temperature is usually limited by vaporization flammability or chemical breakdown of the fluid Vaporization of the fluid at higher temperatures may adversely affect tempera ture stability because of cool condensed fluid dripping into the bath from the lid The bath temperature should be limited by setting the safety cut out so that the bath temperature cannot exceed the safe operating temperature limit of the fluid 8 1 2 Viscosity Viscosity is a measure of the thickness of a fluid or how easily it can be poured and mixed Viscosity affects the temperature uniformity and stability of the bath With lower viscosity fluid mixing is better there fore creating a more uniform temperature throughout the bath Thi
34. ation points are chosen to be 30 00 and 80 00 C The measured bath temperatures are 29 843 and 79 914 C respectively Refer to Figure 7 for applying equations to the example data and com puting the new probe constants 0 00385 1 00 000 100 077 0 00385 0 0038416 40 Manual Rev 722602 Hart Scientific Charging Instructions 12 Charging Instructions The 7025 uses R 404a refrigerant with a polyolester oil Care must be taken to avoid contamination from other types of refrigerants and oils 12 1 Leak Testing Leak testing should be done with equipment designed for use with R 404a Bubble or ultra sonic leak testing may be viable in some instances 12 2 Evacuation DO NOT leave the system open for more than 15 minutes Polyolester oils are very hygroscopic Evacu Model 7025 ate the system to a minimum of 200 microns Evacu ate from both high and low sides of the system Schrader valves provide access to the system 12 3 Charging After evacuation charge the system with a static charge to bottle pressure with R 404a Complete the charge with a fluid in the bath tank With the compres sor running verify that the suction pressure is 14 15 psi then slowly charge from the suction side until the sight glass just fills Manual Rev 722602 41 Maintenance 13 Maintenance The calibration instrument has been designed with the utmost care Ease of operation and simplicity of maintenance have been a central the
35. ation report If the problem reoccurs then the battery should be replaced Contact Hart Scientific Customer Service for assistance initializing the memory does not remedy the problem there may be a failed electronic component Contact Hart Scientific Customer Service for assistance Manual Rev 722602 43 Troubleshooting 14 1 4 The Displayed Process Temperature Is In Error And The Controller Remains In The Cooling Or The Heating State At Any Set point Value Possible causes may be either a faulty control probe or erroneous data in memory The probe may be disconnected burned out or shorted Check that the probe is connected properly The probe may be checked with an ohmmeter to see if it is open or shorted The probe is a platinum 4 wire Din 43760 type therefore the resistance should read 0 2 to 2 0 ohms between pins 1 and 2 on the probe connector and 0 2 to 2 0 ohms between pins 3 and 4 The resistance should read from 100 to 300 ohms be tween pins 1 and 4 depending on the temperature If the probe is defective contact Hart Scientific Cus tomer Service for assistance If the problem is not the probe erroneous data in memory may be the cause Re initialize the memory as discussed in Seqtion 14 113 above If the problem remains the cause may be a defective electronic component Contact Hart Scientific Customer Service for assistance 14 1 5 The Controller Controls Or Attempts To Control At An Inaccurate Temperature Th
36. ay failure or other circuit failure the microcontroller will automatically turn off the heater with a second mechanical relay anytime the bath temperature is more than a certain amount above the set point temperature As a second protection device the controller is also equipped with a separate ther mocouple temperature monitoring circuit which will shut off the heater if the temperature exceeds the cut out set point The controller allows the operator to set the bath temperature with high resolution set the cut out ad just the proportional band monitor the heater output power and program the controller configuration and calibration parameters The controller may be oper ated in temperature units of degrees Celsius or Fahr enheit The controller is operated and programmed from the front control panel using the four key switches and digital LED display The controller may also be optionally equipped with an RS 232 serial or IEEE 488 GPIB digital interface for remote operation Op Model 7025 General Operation eration of the controller using the front control panel is discussed following in Segtion Y Operation using the digital interfaces is discussed in Section TU When the controller is set to a new set point the bath will heat or cool to the new temperature Once the new temperature is reached the bath usually takes 10 15 minutes for the temperature to settle and stabilize There may be a small overshoot or undershoot of
37. be These parameters may be adjusted to improve the accuracy of the bath This procedure is explained in detail in Seftion TT The probe parameters are accessed by pressing SET after the name of the parameter is displayed The value of the parameter may be changed using the UP and DOWN buttons After the desired value is reached press SET to set the parameter to the new value Pressing EXIT will cause the parameter to be skipped ignoring any changes that may have been made 9 10 1 Ro This probe parameter refers to the resistance of the control probe at O C Normally this is set for 100 000 ohms 9 10 2 ALPHA This probe parameter refers to the average sensitivity of the probe between 0 and 100 C Normally this is set for 0 00385 9 11 Operating Parameters The operating parameters menu is indicated by PAr Operating parameters menu Press UP to enter the menu The operating parame ters menu contains the cut out reset mode parameter 32 Manual Rev 722602 9 11 1 Cut out Reset Mode The cut out reset mode determines whether the cut out resets automatically when the bath temperature drops to a safe value or must be manually reset by the operator The parameter is indicated by Cut out reset mode parameter Press SET to access the parameter setting Nor mally the cut out is set for automatic mode Cut out set for automatic reset 9 12 Serial Interface Parameters The serial RS 232 interface
38. ber indicates the number of times power has been applied to the bath Also briefly displayed is data which indicates the controller hardware configuration This data is used in some circumstances for diagnostic purposes 8 4 Heater The power to the bath heater is precisely controlled by the temperature controller to maintain a constant bath temperature Power is controlled by periodically switching the heater on for a certain amount of time using a solid state relay The front panel red green control indicator shows the state of the heater The control indicator glows red when the heater is on and glows green when the heater is off The indicator will pulse constantly when the bath is maintaining a stable temperature 8 5 Temperature Controller The bath temperature is controlled by Hart Scientific s unique hybrid digital analog temperature controller The controller offers the tight control stability of an analog temperature controller as well as the flexibility and programmability of a digital controller The bath temperature is monitored with a platinum resistance sensor in the control probe The signal is electronically compared with the programmable refer ence signal amplified and then passed to a pulse width modulator circuit which controls the amount of power applied to the bath heater Hart Scientific The bath is operable within the temperature range given in the specifications For protection against solid state rel
39. c Cus tomer Service to be sure that the proposed method will not damage the equipment If the instrument is used in a manner not in accordance with the equipment design the operation of the bath may be impaired or safety hazards may arise The over temperature cut out should be checked every 6 months to see that it is work ing properly In order to check the user selected cut out follow the controller directions Sefton ___ 9 8 for setting the cut out Both the manual and the auto reset option of the cut out should be checked Set the bath temperature higher than the cut out Check to see if the display flashes cut out and the temperature is de creasing Note When checking the over temperature cut out be sure that the temperature limits of the bath fluid are not exceeded Exceeding the temperature lim its of the bath fluid could cause harm to the operator lab and instrument Hart Scientific 14 Troubleshooting 14 4 Troubleshooting In the event the bath appears to function abnormally this section may help to find and solve the problem oeveral possible problem conditions are described along with likely causes and solutions If a problem arises please read this section carefully and attempt to understand and solve the problem If the bath seems faulty or the problem cannot otherwise be solved then contact Hart Scientific Customer Service for assistance A wiring diagram is also included Opening the unit without con
40. e units The optimum proportional band width setting may be determined by monitoring the stability with a high resolution thermometer or with the controller percent output power display Narrow the proportional band width to the point at which the bath temperature begins to oscillate and then increase the band width from this point to or 4 times wider Table 31519 typical proportional band settings for optimum performance with a variety of fluids at selected temperatures The proportional band adjustment may be accessed within the secondary menu Press and EXIT to enter the secondary menu and show the heater Fluid Temperature Proportional Band Stability Water 30 0 C 0 04 C 0 002 C Water 60 0 C 0 04 C 0 002 C Eth Gly 50 35 0 C 0 05 C 0 002 C Eth Gly 50 60 0 C 0 05 C 0 002 Eth Gly 50 100 0 C 0 1 10 007 C Oil 35 0 C 0 1 C 0 004 Oil 60 0 C 0 2 C 0 004 Oil 100 C 0 2 C 0 004 30 Manual Rev 722602 Hart Scientific power Then press SET to access the proportional band t Access heater power in secondary menu Heater power in percent change the proportional band press UP or DOWN Decrement display New proportional band setting accept the new setting and access the cut out set point press SET Pressing EXIT will exit the secondary menu ignoring any changes just made to the proportional band value Accept new propor
41. e controller operates normally except when control ling at a specified set point At this set point the temperature does not agree with that measured by the user s reference thermometer to within the speci fied accuracy This problem may be caused by an actual difference in temperature between the points where the control probe and thermometer probe measure temperature by erroneous bath calibration parameters or by a damaged control probe Check that the bath has an adequate amount of fluid in the tank and that the stirrer is oper ating properly Check that the thermometer probe and control probe are both fully inserted into the bath to minimize temperature gradient errors Check that the calibration parameters are all correct according to the certification sheet If notthen reprogram the constants The memory 44 Manual Rev 722602 backup battery may be weak causing errors in data as described in Sefton 14 7 3 Check that the control probe has not been struck bent or damaged If the cause of the problem remains unknown contact Hart Sci entific Customer Service for assistance 14 1 6 The Controller Shows That The Output Power is Steady But The Process Temperature is Unstable If the bath temperature does not achieve the expected degree of stability when measured using a thermome ter try adjusting the proportional band to a narrower width as discussed in Seftion 9 7 14 1 7 The Controller Alternate
42. e set point access and set other operating parameters and access and set bath calibration parameters A brief description of the functions of the buttons follows Used to display the next parameter in a menu and to set parameters to the displayed value DOWN Used to decrement the displayed value of parameters UP Used to increment the displayed value HART SCIENTIFIC Figure 2 Front Panel Features 18 Manual Rev 722602 EXIT Used to exit from a menu When EXIT is pressed any changes made to the displayed value will be ignored 3 The on off switch controls power to the entire bath including the stirring motor 4 The control indicator is a two color light emitting diode LED This indicator lets the user visually see the ratio of heating to cooling When the indicator is red the heater is on and when it is green the heater is off and the bath is cooling 5 The cooling switch turns on the refrigeration for control below 45 C and rapid cool down 7 2 Bath Tank and Lid The bath tank and lid assembly includes the tank the control probe the stirring motor the access hole and the access hole cover The 7025 bath also has a heat shield mounted on the lid to protect the user from the hot top surface of the bath e The bath tank is constructed of stainless steel lt is very resistant to oxidation in the presence of most chemicals and over a wide range of temperatures 7025 High Precision
43. e temperature and access any of the other controller functions all using remote communications equipment In addition the cooling may be controlled using the interface To control the cooling with the interface the cooling power switch must be OFF 10 4 Serial Communications The bath may be installed with an RS 232 serial interface that allows serial digital communications over fairly long distances With the serial interface the user may access any of the functions parameters and settings discussed in Sefton Y with the exception of the BAUD rate setting 10 1 1 Wiring The serial communications cable attaches to the bath through the DB 9 connector at the back of the instru ment Figure 6 Shows the pin out of this connector and suggested cable wiring To eliminate noise the serial cable should be shielded with low resistance between the connector DB 9 and the shield 10 1 2 Setup Before operation the serial interface of the bath must first be set up by programming the BAUD rate and other configuration parameters These parameters are programmed within the serial interface menu To enter the serial parameter programming mode first press EXIT while pressing SET and release to enter the secondary menu Press SET repeatedly until the display reads Probst This is the menu selection Press UP repeatealy until the serial inter face menu is indicated with SEr AL Finally press Model 7025 SET to enter the s
44. e temperatures Precau tions must be taken to prevent personal injury or damage to objects Probes may be extremely hot or cold when removed from the bath Cautiously handle probes to prevent personal injury Carefully place probes on a heat cold resistant surface or rack until they are at room temperature It is advisable to wipe the probe with a clean soft cloth or paper towel before inserting it into another bath This prevents the mixing of fluids from one bath to another If the probe has been calibrated in liquid salt carefully wash the probe in warm water and dry completely before transferring it to another fluid Always be sure that the probe is completely dry before inserting it into a hot fluid Some of the high temperature fluids react violently to water or other liquid mediums Be aware that cleaning the probe can be dangerous if the probe has not cooled to room temperature Additionally high temperature fluids may ignite the paper towels if the probe has not been cooled For optimum accuracy and stability allow the bath adequate stabilization time after reaching the set point temperature 16 Manual Rev 722602 6 2 Comparison Calibration Comparison calibration involves testing a probe unit under test UUT against a reference probe After inserting the probes to be calibrated into the bath allow sufficient time for the probes to settle and the temperature of the bath to stabilize One of the significant dividends of u
45. erial parameter menu In the serial interface parameters menu are the BAUD rate the sample rate the duplex mode and the linefeed pa rameter 10 1 2 1 BAUD Rate The BAUD rate is the first parameter in the menu The display will prompt with the BAUD rate parameter by showing BRUd Press SET to choose to set the BAUD rate The current BAUD rate value will then be displayed The BAUD rate of the 7025 serial commu nications may be programmed to 300 600 1200 or 2400 BAUD The BAUD rate is pre programmed to 1200 BAUD Use UP or DOWN to change the BAUD rate value Press SET to set the BAUD rate RS 232 Cable Wiring for IBM PC and Compatibles Instrument Connector DB 9 Pin Computer DTE Connector DB 25 Pin 1 NC e 2 RxD e 2 TxD 3 TxD 3 RxD 4 NC e 5 GNDe 6 NC 7 RTS 8 CTS e 9 NC eo Instrument Connector DB 9 Pin 1 NC 2 RxD 3 TxD 4 NC e 5 GND e 6 NC e Computer DTE Connector DB 9 Pin e 1 NC 2 RxD e 3 TxD e e 4 NC 5 GND e e 6 NC 7 RTS e e 7 RTS 8 CTS e 8 CTS 9 NC e e 9 NC Figure 6 Serial Communications Cable Wiring Manual Hev 722602 Jo Digital Communication Interface to the new value or EXIT to abort the operation and skip to the next parameter in the menu 10 1 2 2 Sample Period The sample period is the next parameter in the menu and prompted with SAMPL
46. ficant The vapors may be dangerous and a fume hood should be used As with most oils mineral oil will expand as temperature increases so be careful not to fill the bath too full that it overflows when heated The viscosity and thermal characteristics of mineral oil is Manual Rev 722602 21 General Operation 200 C Dow Corning 710 Dow Corning 200 20 ENN 200 10 RA vo 200 05 RR Dow Corning 550 Halocarbon 0 8 Mineral Oil Water Methanol Ethylene Glycol 50 50 with H O Heat Transfer Salt Point above which a fume hood is recommended BP Boiling Point CS Centistokes EP Evaporation Point fluid loss due to evaporation is too high FL Flash Point FR Freeze Point PP Pour Point 300 C 400 C 500 C Decomposition Starts Shaded area represents usable range of fluid starting at 50 Centistokes Lighter shading represents decreasing viscosity while vaporization and decomposition increases The hatched area represents liquid range with excessive viscosity Figure 3 Chart showing usable range of various fluids poorer than water so temperature stability will not be as good Mineral oil has very low electrical conductiv ity Use caution with mineral oil since it is flammable and may also cause serious injury if inhaled or in gested 8 1 10 4 Silicone Oil Silicone oils are available which offer a much wider operating temperature range than mineral oil Like most oils s
47. ilicone oils have temperature control char acteristics which are somewhat poorer than water The viscosity changes significantly with temperature and thermal expansion also occurs These oils have very high electrical resistivity Silicone oils are fairly safe and non toxic Silicone oils are fairly expensive 22 Manual Rev 722602 8 1 11 Fluid Characteristics Charts 2 ang Figure 3 on pages 23 22 ngve been created to provide help in selecting a heat exchange fluid media for your constant temperature bath These charts provide both a visual and numerical repre sentation of most of the physical qualities important in making a selection The list is not all inclusive There may be other useful fluids not shown in this listing The charts include information on a variety of fluids which are often used as heat transfer fluid in baths Because of the temperature range some fluids may not be useful with your bath Hart Scientific Table 2 Table of Bath Fluids General Operation Fluid Lower Upper Specific Thermal Thermal Hart Temperature Temperature Flash Viscosity Specific Heat Conductivity Expansion Resistivity Part No Limit Limit Point centistokes Gravity cal g C cal sicm C cm cm C 10120 cm Halocarbon 90 C v 70 C e 5 7 50 C 1 71 40 0 2 0 0004 0 001 1 0 8 5019 0 8 40 C 0 5 70 C Methanol 96 C fr 60 b 54
48. ly Heats For A While then Cools This oscillation is typically caused by the proportional band being too narrow Increase the width of the proportional band until the temperature stabilizes as discussed in Se tion 9 7 14 1 8 The Controller Erratically Heats Then Cools Control Is Unstable If both the bath temperature and output power do not vary periodically but in a very erratic manner the problem may be excess noise in the system Noise due to the control sensor should be less than 0 001 C However if the probe has been damaged or has developed an intermittent short erratic behavior may exist Check for a damaged probe or poor connection between the probe and bath Intermittent shorts in the heater or controller elec tronic circuitry may also be a possible cause Contact Hart Scientific Customer Service for assistance 14 1 9 The Bath Does Not Achieve Low Temperatures This problem can be caused by too much heating or not enough cooling Check that the control indicator glows green showing that the controller is attempting to cool The heaters may be disabled as a test by temporarily removing the heater fuses Hart Scientific Troubleshooting Maximize cooling by switching the cooling on setting Insufficient cooling may be caused by lack of refriger the cooling power to high if applicable and setting the ant because of a leak in the system Refer to the cooling temperature to 10 15 C below the bath set Charging
49. m mondo don wed oe i amp 25 Controller Operation 26 9 1 Bath Temperature 26 die eset UROL dm 26 9 9 Temperature ue sede eae is oak D rade e eer EO uA 26 9 3 1 Programmable Set points 26 932 SEHON cae ams xh End SS AD 28 SEDO Vernier 2 3 uod ere Sel wR TELE da IER Y 28 9 4 Temperature Scale Units 28 9 5 Secondary Menu 20 64 bad dee Rab woe Be GR e od 29 9 6 Healer xe dd robo dus de CE S he Xs edis cle vi 29 Tropordonal ose unb a oO oe Oe ad de 29 GUIEOUL T 31 9 9 Controller Configuration 31 9 10 Probe Parameters uude cde uk bl d Xe oie ni es 32 O01 Sarai uda P bu wee 32 911002 ALPHA 6432646256 oad oie dus d ea 32 9 11 Operating Parameters 32 GUIEQUE eset ModE soie aE A SE AA 32 9 12 Serial Interface Parameters 32 9 121 BAUDRate 32 RUE 33
50. me in the prod uct development Therefore with proper care the in strument should require very little maintenance Avoid operating the instrument in dirty or dusty environ ments 42 If the outside of the bath becomes soiled it may be wiped clean with a damp cloth and mild detergent Do not use harsh chemicals on the surface which may damage the paint Periodically check the fluid level in the bath to ensure that the level has not dropped A drop in the fluid level affects the stability of the bath Changes in fluid level are dependent upon several factors specific to the environment in which the equipment is used A schedule can not be outlined to meet each environmental setting Therefore the first year the bath should be checked weekly with notes kept as to changes in bath fluid After the first year the user can set up a maintenance schedule based on the data specific to the application Heat transfer medium lifetime is dependent upon the type of medium and the environment The fluid should be checked at least every month for the first year and regularly thereafter This fluid check provides a baseline for knowl edge of bath operation with clean usable fluid Once some fluids have become compromised the break down can occur rapidly Particular attention should be paid to the viscosity of the fluid A significant change in the viscosity can indicate that the fluid is contaminated being used outside of its temperature li
51. mits contains ice particles or is close to a chemical break down Once data has been gathered a specific maintenance schedule can be outline for the instrument Refer to the General Operation section Segtion 8 fot more information about the different types of fluids used in calibration baths Depending on the cleanliness of the environ ment the internal parts parts behind the front cover only of the cold bath should be cleaned Manual Rev 722602 and or checked at least every month for dust and dirt Particular attention should be paid to the condensing coil fins The fins should be vacuumed or brushed free of dust and dirt on a regular basis Dust and dirt inhibit the opera tion of the condensing coil and thus compro mise the performance and life time of the cooling system If a hazardous material is spilt on or inside the equipment the user is responsible for taking the appropriate decontamination steps as out lined by the national safety council with respect to the material MSDS sheets applicable to all fluids used in the baths should be kept in close proximity to the instrument If the mains supply cord becomes damaged replace it with a cord with the appropriate gauge wire for the current of the bath If there are any questions call Hart Scientific Cus tomer Service for more information Before using any cleaning or decontamination method except those recommended by Hart users should check with Hart Scientifi
52. mperature drops If the mode is set to RESET the heater only comes on again when the temperature is reduced and the cut out is manually reset by the operator See Sefton 9 8 Check that the cut out set point is adjusted to 10 or 20 above the maximum bath operating tempera ture and that the cut out mode is set as desired If the cut out activates when the bath temperature is well below the cut out set point or the cut out does not reset when the bath temperature drops and it is manually reset then the cut out circuitry may be faulty or the cut out thermocouple sensor may be faulty or disconnected Contact Hart Scientific Customer Serv ice for assistance 14 1 3 The Display Flashes CUT OUT And An Incorrect Process Temperature The problem may be that the controllers voltmeter circuit is not functioning properly A problem could exist with the memory back up battery If the battery voltage is insufficient to maintain the memory data may become scrambled causing problems A nearby large static discharge may also affect data in memory The memory may be reset by holding the SET and EXIT keys down while power to the controller is switched on The display shows init indicating the memory is being initialized At this point each of the controller parameters and calibration constants must be reprogrammed into memory You can obtain the calibration constants from the test results sheet of the calibr
53. ns mitting temperature readings at the programmed rate The set point and other commands may be sent to the bath via the serial interface to set the bath and view or program the various parameters The interface com mands are discussed in Seqtion 10 3 36 Manual Rev 722602 10 2 488 Communication optional The IEEE 488 interface is available as an option Baths supplied with this option may be connected to a GPIB type communication bus which allows many instruments to be connected and controlled simulta neously To eliminate noise the GPIB cable should be shielded 10 2 1 Setup To use the IEEE 488 interface first connect an IEEE 488 standard cable to the back of the bath Next set the device address This parameter is programmed within the IEEE 488 interface menu To enter the IEEE 488 parameter programming menu first press EXIT while pressing SET and release to enter the secondary menu Press SET repeatedly until the display reaches Pr This is the menu selection Press UP repeatedly until the IEEE 488 interface menu is indicated with IEEE Press SET to enter the IEEE 488 parameter menu The IEEE 488 menu contains the IEEE 488 address parameter 10 211 IEEE 488 Interface Address The IEEE 488 address is prompted with Addr E55 Press SET to program the address The default address is 22 Change the device address of the bath if necessary to match the address used by the com
54. ortional band is too narrow the bath temperature may swing back and forth because the controller overreacts to temperature variations For best control stability the proportional band must be set for the optimum width The optimum proportional band width depends on several factors among which are fluid volume fluid characteristics viscosity specific heat thermal con ductivity heater power setting operating tempera ture and stirring Thus the proportional band width Manual Hev 722602 29 Controller Operation wwii MT Proportional Band too Narrow Proportional Band too Wide Optimum Proportional Band 99 MM Figure 5 Bath temperature fluctuation at various proportional band settings may require adjustment for best bath stability when any of these conditions change Of these the most significant factors affecting the optimum proportional band width are heater power setting and fluid viscos ity The proportional band should be wider when the higher power setting is used so that the change in output power per change in temperature remains the same The proportional band should also be wider when the fluid viscosity is higher because of the increased response time The proportional band width is easily adjusted from the bath front panel The width may be set to discrete values in degrees C or F depending on the selected Table 3 Proportional Band Fluid Tabl
55. ours before it can be assumed to meet all of the safety requirements of the IEC 1010 1 5 3 Bath Preparation and Filling The Model 7025 Bath is not provided with a fluid Various fluids are available from Hart Scientific and other sources Depending on the desired temperature range any of the following fluids as well as others may be used in the bath e Water e Ethylene glycol water Model 7025 Installation e Mineral oil e Silicone oil Fluids are discussed in detail in Setion 8 1 Remove any access hole cover from the bath and check the tank for foreign matter dirt remnant pack ing material etc Fill the bath with clean unpolluted fluid Fill the bath carefully through the large square access hole to a level that will allow for stirring and thermal expansion DO NOT turn on the bath without fluid in the tank The fluid should never exceed a height of 1 2 below the top of the tank Carefully monitor the bath fluid level as the bath temperature rises to prevent overflow or splashing Remove excess hot fluid if necessary with caution 5 4 Probe Inspect the bath controller probe It should not be bent or damaged in any way Reasonable caution should be used in handling this probe as it contains a preci sion platinum sensor and is mechanically shock sen sitive Dropping striking or other physical shock may cause a shift in resistance in the probe resulting in diminished bath accuracy If damaged the probe c
56. ower should not fluctuate more than 1 within one minute The heater power display is accessed in the secon dary menu Press SET and EXIT simultaneously and release The heater power will be displayed as a percentage of full power Access heater power in secondary menu Heater power in percent To exit out of the secondary menu press EXIT To continue on to the proportional band setting function press SET Return to temperature display 9 7 Proportional Band In a proportional controller such as this the heater output power is proportional to the bath temperature over a limited range of temperatures around the set point This range of temperature is called the propor tional band At the bottom of the proportional band the heater output is 10096 At the top of the proportional band the heater output is 0 Thus as the bath tempera ture rises the heater power is reduced which conse quently tends to lower the temperature back down In this way the temperature is maintained at a fairly constant temperature The temperature stability of the bath depends on the width of the proportional band See Figure 5 Tf the band is too wide the bath temperature will deviate excessively from the set point due to varying external conditions This is because the power output changes very little with temperature and the controller cannot respond very well to changing conditions or noise in the system If the prop
57. parameters menu is indi cated by rameters menu The serial interface parameters menu contains pa rameters which determine the operation of the serial interface These controls only apply to baths fitted with the serial interface The parameters in the menu are BAUD rate sample period duplex mode and linefeed 9 12 1 BAUD Rate The BAUD rate is the first parameter in the menu The BAUD rate setting determines the serial communica tions transmission rate The BAUD rate parameter is indicated by Serial BAUD rate parameter Press SET to choose to set the BAUD rate The current BAUD rate value will then be displayed Current BAUD rate Hart Scientific The BAUD rate of the bath serial communications may be programmed to 300 600 1200 or 2400 BAUD Use UP or DOWN to change the BAUD rate value New BAUD rate Press SET to set the BAUD rate to the new value or EXIT to abort the operation and skip to the next parameter in the menu 9 12 2 Sample Period The sample period is the next parameter in the serial interface parameter menu The sample period is the time period in seconds between temperature meas urements transmitted from the serial interface If the sample rate is set to 5 for instance then the bath will transmit the current measurement over the serial interface approximately every five seconds The auto matic sampling is disabled with a sample period of
58. per and lower case letters hence either may be used Commands may be abbreviated to the minimum number of letters which determines a unique command A command may be used to either set a parameter or display a parameter depending on whether or not a value is sent with the command following a character For example s lt CR gt will return the current set point and 5 50 00 CR will set the set point to 50 00 de grees In the following list of commands characters or data within brackets and are optional for the com mand A slash denotes alternate characters or data Numeric data denoted by n may be entered in decimal or exponential notation Characters are 38 Manual Rev 722602 10 3 1 shown in lower case although upper case may be used Spaces may be added within command strings and will simply be ignored Backspace BS ASCII 8 may be used to erase the previous character A termi nating CR is implied with all commands Cooling Control To control the refrigeration power with the serial inter face the front panel cooling switch must be off The refrigeration power function is controlled with serial F2 command Setting the F2 value to 0 turns the refrigeration off and setting itto 1 turns iton F2 alone will return O or 1 showing the state of the refrigeration power control Hart Scientific Calibration Procedure 11 Calibration Procedure In some instances the u
59. perature Thermal expan sion of the fluid must be considered since the increase in fluid volume as the bath temperature increases may cause overflow Excessive thermal expansion may also be undesirable in applications where constant liquid level is important Many fluids including oils have Significant thermal expansion 8 1 6 Electrical Resistivity Electrical resistivity describes how well the fluid insu lates against the flow of electric current In some applications such as measuring the resistance of bare temperature sensors it may be important that little or no electrical leakage occur through the fluid Hart Scientific In such conditions choose a fluid with very high elec trical resistivity 8 1 7 Fluid Lifetime Many fluids degrade over time because of vaporiza tion water absorption gelling or chemical break down Often the degradation becomes significant near the upper temperature limit of the fluid substan tially reducing the fluid s lifetime 8 1 8 Safety When choosing a fluid always consider the safety issues associated Obviously where there are ex treme temperatures there can be danger to personnel and equipment Fluids may also be hazardous for other reasons Some fluids may be considered toxic Contact with eyes skin or inhalation of vapors may cause injury A proper fume hood must be used if hazardous or bothersome vapors are produced WARNING Fluids at high temperatures may pose danger f
60. point The front panel LED display will indicate the actual bath temperature oet the cooling switch to OFF for temperatures above approximately 45 C Set the switch to ON for lower temperatures 4 4 Setting the Temperature In the following discussion and throughout this man ual a solid box around the word SET UP DOWN or EXIT indicates the panel button to press while the dotted box indicates the display reading on the front panel Explanation of the button function or display reading is written at the right To view or set the bath temperature set point proceed as follows The front panel LED display normally shows the actual bath temperature Bath temperature display When SET is pressed the display will show the set point memory that is currently being used and its value Eight set point memories are available Access set point selection Set point 1 25 0 C currently used Press SET to select this memory and access the set point value Access set point value Current value of set point 1 RC 25 00C Press UP or DOWN to change the set point value Manual Rev 722602 13 Quick Start Increment display New set point value Press SET to accept the new value and display the vernier value The bath begins heating or cooling to the new set point SET Store new set point access vernier Current vernier value Press EXIT and the bath temperature will be dis
61. rallOll s WIR uL IA E COP 36 10 3 Interface COMMANOS s dis ad amp oe OS e EE ORR 36 SOONG CONTON ao Ay Sect te E Se e BA BO we Se ver 38 11 Calibration Procedure 39 A SCAND ATOM POINTS a uu de acce nh ae dedo Re xo m 39 11 2 Measuring the Set point Error 39 11 3 Computing Ro and ALPHA oko Oo E E em Ew 39 11 4 Calibration Example 40 12 Charging Instructions 41 12 4 LeakTesting 41 12 2 ex mune RUE ES oo Ra d Rx 41 12 9 Charging s d 645024664568 4348 6S oo ee 41 13 Maintenance 42 14 ING EROR E E OR cs OE 43 141 TKOUDIGSHOOUNG x uo UR a YES Be ed 43 14 1 1 The Heater Indicator LED Stays Red But the Temperature Does Not Increase 43 14 1 2 The Controller Display Flashes CUT OUT And The Heater Does Not Operate 43 14 1 3 The Display Flashes CUT OUT And An Incorrect Process Temperature 43 14 1 4 The Displayed Process Temperature Is In Error And The Controller Remains In The Cooling or The Heating State At Any Set point Value
62. ranty Hart Scientific Inc will not apply if the product has not been used accord 799 East Utah Valley Drive ing to the instruction manual or has been tampered American Fork UT 84003 with by the user For service or assistance please Phone 801 663 1600 Fax 801 763 1010 contact the manufacturer Internet http www hartscientific com Model 7025 Manual Hev 722602 11 3 Safety Guidelines 12 Safety Guidelines Operate the bath in room temperatures be tween 5 50 C 41 122 P Allow sufficient air circulation by leaving at least 6 inches of space between the bath and nearby objects Over head clearance needs to allow for safe and easy insertion and removal of probes for cali bration If the bath is used at higher temperatures where fluid vaporization is significant a fume hood should be used The bath is a precision instrument Although it has been designed for optimum durability and trouble free operation it must be handled with care The instrument should not be operated in excessively dusty or dirty environments Do not operate near flammable materials The bath generates extreme temperatures Precautions must be taken to prevent personal injury or damage to objects Probes may be extremely hot or cold when removed from the bath Cautiously handle probes to prevent per sonal injury Carefully place probes on a heat cold resistant surface or rack until they are at room temperature Use only a grounded AC main
63. recommendations can be found in the Maintenance Section of this manual The instrument operates safely under the following conditions Table 1 Specifications temperature range 5 50 41 122 e ambient relative humidity 15 5096 e pressure 75 106kPa e mains voltage within 10 of nominal e vibrations in the calibration environment should be minimized e altitude does not effect the performance or safety of the unit 2 3 Warranty The 7025 bath is covered by a 2 year warranty that takes effect 10 days after the product is shipped The manufacturer will provide parts and labor without charge for repair or replacement of the instrument due Operating Range 20 to 110 C Temperature Stability 0 005 C or better Temperature Gradients 0 01 C max between any two points in the work area Set point Accuracy 0 5 C or better Cut out Accuracy 5 C Exterior Dimensions Width 20 2 inches Front to back 15 88 inches Height 12 2 inches to working surface 15 5 inches to top of stirring motor Power Requirements 115 VAC 10 single phase 60 Hz 230 VAC 10 50 Hz Optional Weight 55 lbs Fluid Volume Approximately 2 1 gallons Working Area 5 3 4 W x 3 1 4 Front to Back x 7 1 2 Deep 10 Manual Rev 722602 Hart Scientific Specifications and Environmental Conditions to defects in material or workmanship The war
64. resets the cut out The cut out set point may be accessed within the secondary menu Press SET and EXIT to enter the secondary menu and show the heater power Then press SET twice to access the cut out set point Access heater power in secondary menu Heater power in percent To change the cut out set point press UP or DOWN Decrement display New cut out set point To accept the new cut out set point press SET Accept cut out set point The next function is the configuration menu Press EXIT to resume displaying the bath temperature 9 9 Controller Configuration The controller has a number of configuration and operating options and calibration parameters which are programmable via the front panel These are accessed from the secondary menu after the cut out set point function by pressing SET There are 5 sets of configuration parameters probe parameters operating parameters serial interface parameters Manual Hev 722602 31 Controller Operation IEEE 488 interface parameters and controller cali bration parameters The menus are selected using the UP and DOWN keys and then pressing SET 9 10 Probe Parameters The probe parameter menu is indicated by Probe parameters menu Press SET to enter the menu The probe parameters menu contains the parameters R and ALPHA which characterize the resistance temperature relationship of the platinum control pro
65. rom B URNS FIRE and TOXIC FUMES Use appropriate caution and safety equipment Fluids may be flammable and require special fire safety equipment and procedures An important char acteristic of the fluid to consider is the flash point The flash point is the temperature at which there is suffi cient vapor given off so that when there is adequate oxygen present and a ignition source is applied the vapor will ignite This does not necessarily mean that fire will be sustained at the flash point The flash point may be either of the open cup or closed cup type Either condition may occur in a bath situation The open cup flash point is measured under the condition of vapors escaping the tank The closed cup flash point is measured with the vapors being contained within the tank Since oxygen and an ignition source is less available inside the tank the closed cup flash point will be lower than the open cup flash point Environmentally hazardous fluids require special dis posal according to applicable federal or local laws after use Model 7025 General Operation 8 1 9 Cost Cost of bath fluids may vary greatly from cents per gallon for water to hundreds of dollars per gallon for synthetic oils Cost may be an important consideration when choosing a fluid 8 1 10 Commonly Used Fluids Below is a description of some of the more commonly used fluids and their characteristics 8 1 10 1 Water Water is often used because of its ve
66. ry low cost its availability and its excellent temperature control char acteristics Water has very low viscosity and good thermal conductivity and heat capacity which makes it among the best fluids for good control stability at lower temperatures Temperature stability is much poorer at higher temperatures because water con denses on the lid cools and drips into the bath Water is safe and relatively inert The electrical conductivity of water may prevent its use in some applications Water has a limited temperature range from a few degrees above 0 C to a few degrees below 100 C At higher temperatures evaporation becomes signifi cant Water used in the bath should be distilled or deionized to prevent mineral deposits Consider using an algicide chemical in the water to prevent contami nation 8 1 10 2 Ethylene Glycol The temperature range of water may be extended by using a solution of 1 part water and 1 part ethylene glycol antifreeze The characteristics of the ethylene glycol water solution are similar to water but with higher viscosity Use caution with ethylene glycol since this fluid is very toxic Ethylene glycol must be disposed of properly 8 1 10 3 Mineral Oil Mineral oil or paraffin oil is often used at moderate temperatures above the range of water Mineral oil is relatively inexpensive At lower temperatures mineral oil is quite viscous and control may be poor At higher temperatures vapor emission becomes signi
67. s improves the bath response time which allows it to maintain a more constant temperature For good control the viscosity should be less than 10 centistokes 50 centistokes is about the practical up per limit of allowable viscosity Viscosity greater than this causes very poor control stability because of poor stirring and may also overheat or damage the stirring 20 Manual Rev 722602 motor Viscosity may vary greatly with temperature especially with oils When using fluids with higher viscosities the controller proportional band may need to be increased to com pensate for the reduced response time Otherwise the temperature may begin to oscillate 8 1 3 Specific Heat Specific heat is the measure of the heat storage ability of the fluid Specific heat to a small degree affects the control stability It also affects the heating and cooling rates Generally a lower specific heat means quicker heating and cooling The proportional band may require some adjustment depending on the spe cific heat of the fluid 8 1 4 Thermal Conductivity Thermal conductivity measures how easily heat flows through the fluid Thermal conductivity of the fluid affects the control stability temperature uniformity and temperature settling time Fluids with higher con ductivity distribute heat more quickly and evenly im proving bath performance 8 1 5 Thermal Expansion Thermal expansion describes how much the volume of the fluid changes with tem
68. s supply of the appropriate voltage to power the bath The Manual Hev 722602 bath requires 8 amps at 115V AC 10 60 Hz 4 amps at 230 VAC 10 50 Hz op tional Before initial use after transport and anytime the instrument has not been energized for more than 10 days the bath needs to be energized for a dry out period of 1 2 hours before it can be assumed to meet all of the safety requirements of the IEC 1010 1 The bath is equipped with operator accessible fuses If a fuse blows it may be due to a power surge or failure of a component Replace the fuse once If the fuse blows a second time it is likely caused by failure of a component part If this occurs contact Hart Scientific Customer service Always replace the fuse with one of the same rating voltage and type Never re place the fuse with one of a higher current rating If a mains supply power fluctuation occurs immediately turn off the bath Power bumps from brown outs and black outs can damage the compressor Wait until the power has sta bilized before re energizing the bath Hart Scientific 4 Quick Start CAUTION READ SECTION 6 ENTITLED BATH USE before placing the bath in service Incorrect handling can damage the bath and void the warranty This chapter gives a brief summary of the steps required to set up and operate the bath This should be used as a general overview and reference and not as a substitute for the remainder of the manual
69. ser may want to calibrate the bath to improve the temperature set point accuracy Calibration is done by adjusting the controller probe calibration constants and ALPHA so that the tem perature of the bath as measured with a standard thermometer agrees more closely with the bath set point The thermometer used must be able to measure the bath fluid temperature with higher accuracy than the desired accuracy of the bath By using a good thermometer and carefully following procedure the bath can be calibrated to an accuracy of better than 0 02 C over a range of 100 degrees 11 1 Calibration Points In calibrating the bath Ry and ALPHA are adjusted to minimize the set point error at each of two different bath temperatures Any two reasonably separated bath temperatures may be used for the calibration however best results will be obtained when using bath temperatures which are just within the most useful operating range of the bath The further apart the calibration temperatures the larger will be the cali brated temperature range but the calibration error will also be greater over the range If for instance 0 C and 100 C are chosen as the calibration temperatures then the bath may achieve an accuracy of maybe 0 03 C over the range 10 to 110 C Choosing 30 C and 70 C may allow the bath to have a better accuracy of maybe 0 01 C over the range 25 to 75 but outside that range the accuracy may be only 0 05 C 11 2 Measuring the
70. sing a bath rather than a dry well to calibrate multiple probes is that the probes do not need to be identical in construction The fluid in the bath allows different types of probes to be calibrated at the same time However stem effect from different types of probes is not totally eliminated Even though all baths have horizontal and vertical gradi ents these gradients are minimized inside the bath work area Nevertheless probes should be inserted to the same depth in the bath liquid Be sure that all probes are inserted deep enough to prevent stem effect From research at Hart Scientific we suggest a general rule of thumb for immersion depth to reduce the stem effect to a minimum 15 x the diameter of the UUT the sensor length Do not submerge the probe handles If the probe handles get too warm during calibration at high temperatures a heat shield could be used just below the probe handle This heat shield could be as simple as aluminum foil slid over the probe before inserting it in the bath or as compli cated as a specially designed reflective metal appa ratus When calibrating over a wide temperature range better results can generally be achieved by starting at the highest temperature and progressing down to the lowest temperature Probes can be held in place in the bath by using probe clamps or drilling holes in the access cover Other fixtures to hold the probes can be designed The object is to keep the reference probe and
71. sponsible for reading the MSDS material safety data sheets and acting accordingly Manual Rev 722602 23 General Operation 8 1 11 2 About the Graph The fluid graph visually illustrates some of the impor tant qualities of the fluids shown Temperature Range The temperature scale is shown in degrees Celsius The fluids general range of application is indicated by the shaded bands Quali ties including pour point freeze point important vis cosity points flash point boiling point and others may be shown Freezing Point The freezing point of a fluid is an obvious limitation to stirring As the freezing point is approached high viscosity may also limit perform ance Pour Point This represents a handling limit for the fluid Viscosity Points shown are at 50 and 10 centistokes viscosity When viscosity is greater than 50 centis tokes stirring is very poor and the fluid is unsatisfac tory for bath applications Optimum stirring generally occurs at 10 centistokes and below Fume Point The point at which a fume hood should be used This point is very subjective in nature and is impacted by individual tolerance to different fumes and smells how well the bath is covered the surface area of the fluid in the bath the size and ventilation of the facility where the bath is located and other condi tions We assume the bath is well covered at this point This is also subject to company policy Flash Point The point at
72. tacting Hart Scientific Customer Service may void the warranty 14 1 1 The Heater Indicator LED Stays Red But the Temperature Does Not Increase The display does not show cut out nor displays an incorrect bath temperature but the controller other wise appears to operate normally The problem may be either insufficient heating or no heating at all or too much cooling Insufficient heating may be caused by the heater power setting being too low especially at higher operating temperatures Switching to the higher heater power switch setting if available may solve the problem Try reducing cooling capacity by increasing the cooling temperature switching the cooling power switch to LOW or switching off the cooling altogether One or more burned out heaters or blown heater fuses may also cause this problem If the heaters seem to be burned out contact Hart Scientific Customer Serv ice for assistance 14 1 2 The Controller Display Flashes CUT OUT And The Heater Does Not Operate The display will flash CUT OUT alternately with the process temperature If the process temperature dis played seems grossly in error consult Secfion T4 T 3 Normally the cut out disconnects power to the heater when the bath temperature exceeds the cut out set point causing the temperature to drop back down to a Model 7025 Troubleshooting safe value If the cut out mode is set to AUTO the heater switches back on when the te
73. tion temperature set points t and t and the temperature errors err and err into the following equations Ry t err ty J ALPHA 1 1 ALPHA t err 1 ALPHA t err ALPHA 1 ALPHA t4 t If for example Ry and ALPHA were previously set for 100 000 and 0 0038500 respectively and the data for 1 anderr were as given above then the new values Ry and ALPHA would be computed as 110 116 and 0 0038302 respectively Program the new values R and ALPHA into the controller Check the calibration by setting the temperature to and t and measuring the errors again If desired the calibra tion procedure may be repeated again to further im prove the accuracy Manual Hev 722602 39 Calibration Procedure 11 4 Calibration Example The bath is to be used between 25 and 75 C and it is desired to calibrate the bath as accurately as possible for operation within this range The current values for R and ALPHA are 100 000 and 0 0038500 respec Ry 100 000 ALPHA 0 0038500 30 00 C measured t 29 843 C 80 00 C measured t 79 914 C Compute errors err 29 843 30 00 C 0 157 C err 79 914 80 00 C 0 086 C Compute p 9 086 x 30 0 70 157 x 80 0 B 80 0 30 0 Compute ALPHA ALPHA 80 0 30 0 Figure 7 Calibration Example 1 0 00385x80 0 0 157 1 0 00385 x 30 0 0 086 x tively The calibr
74. tional band setting 9 8 Cut out As a protection against software or hardware fault shorted heater triac or user error the bath is equipped with an adjustable heater cut out device that will shut off power to the heater if the bath temperature exceeds a set value This protects the heater and bath materials from excessive temperatures and most importantly protects the bath fluids from being heated beyond the safe operating temperature preventing hazardous vaporization breakdown or ignition of the liquid The cut out temperature is programmable by the operator from the front panel of the controller It must always be set below the upper temperature limit of the fluid and no more than 10 degrees above the upper temperature limit of the bath If the cut out is activated because of excessive bath temperature then power to the heater will be shut off and the bath will cool The bath will cool until it reaches a few degrees below the cut out set point tempera ture At this point the action of the cut out is deter mined by the setting of the cut out mode parameter Model 7025 Controller Operation The cut out has two selectable modes automatic reset or manual reset If the mode is set to automatic then the cut out will automatically reset itself when the bath temperature falls below the reset temperature allowing the bath to heat up again If the mode is set to manual then the heater will remain disabled until the user manually

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