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microK Manual

1. se ee Ee EG EG EG GE EG GE EE GE tnn tnn nhanh nh hh nh chos nsns sas s has s GE EG Ge Ge Gee 65 l 0 SCPI COMMAND SET ER ER EE OE N RE OE ON 00 10 1 Command Terminators dese o oen oo o reno oe do dd Ge ee oo de Ge do na Oe T o eaae ke Ge we od ed si Go de bo ed oe be Ge ee GE ee wo de sucess 66 10 2 SCPI Command Structure issie eds ds N eo o uo cosa ee Ge eg dee sous na deed de Go de eg Ge qo soa Rs er Co de ve euo ras nage oo Ed od de de 66 10 2 1 SCPI Numeric S ffices 1 eter er e rere bete dE H 67 0 2 2 Parametets EE 68 er GE Nr 68 10 3 Making Measurements using SCPI Commands sesse ss ee Ge ee EE ER AG GE Re Ge ses SR AGE Ge Ee ee 69 10 3 1 Measuring Resistance using SCPI Commands eene 69 10 3 2 Measuring Voltage using SCPI Commande 70 10 4 Kieler OES OE N SoSe 70 10 4 1 ele ue Ter KEE 71 I0 4 2 Gommandz OIE AA ER OE EUR Te RE Rue EROR OR OE ER ERE OE EE 72 10 4 3 Command SEhSe EUlNCnen ee esee ee ee ee ee 72 10 4 4 Command SENSe FUNCtion ee ee ee ee ee ee ee ee ee ee ee ee rese 72 10 4 5 Command SENSe CHANNel ee ee ee ee ee ee ee ee ee ee ee ee ee sese 72 10 4 6 Command SENSe CHANNel ee ee ee ee ee ee ee ee ee ee ee ee ee sere 73 10 4 7 Command SENSe VOLTage RANGe ee ee ee ee ee ee ee Se ee 73 10 4 8 Command SENSe VOLTage RANGe ee ee ee ee Ge Se ee nete 73 0 4 9 Command SENSe
2. If commands are sent to the microK s GPIB port they can be terminated by a Line Feed character ASCII 10 Carriage Return character ASCII 13 EOI condition by pulling the EOI line low during the last character of the ASCII string or any combination of these Responses from the microK on the GPIB interface are always terminated by a Line Feed character the microK does not assert EOI at the end of a response 10 2 SCPI Command Structure Commands are arranged in a hierarchical tree similar to directory trees used in personal computers SCPI uses a defined notation to represent the command tree structure Each node in the tree structure is a command keyword with keywords being separated by colons To simplify the description of the SCPI commands the notation represents levels in the tree using horizontal indentations with the root node being the left most column For example the microK includes the following command structure SENSe FUNCTION CHANNEL FREsistance REFerence REFerence RANGe RANGe READ CALibrate Page 66 of 85 OSES Issue 1 01 _ISOT CH CURRent OFFSet OFFSet A valid command is formed by following the tree structure from a root node until a node is reached with no further nodes below it for example in the above command tree we may use SENSe FRESistance REFerence Keywords can be shortened to the first four letters or 3 if the last letter is a vowel To indicate this the notati
3. 7 2 3 Calibrating the 100 O Internal Reference Resistor Repeat the procedure for calibrating the 400 2 internal reference see section 7 2 2 but configure the microK to measure a Default PRT at mA against the internal 00Q reference on the 125 range with channel The command to adjust the value assigned to the 100 internal reference is CAL REF204 R100 Where R100 is the value calculated for the 100 internal reference 7 2 4 Calibrating the 25 O Internal Reference Resistor Repeat the procedure for calibrating the 400 internal reference see section 7 2 2 but configure the microK to measure a Default PRT at mA against the internal 25 reference on the 125 range with channel The command to adjust the value assigned to the 25 internal reference is CAL REF203 R25 Where R25 is the value calculated for the 25Q internal reference 7 2 5 Calibrating the 10 O Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 10 to channel Ideally this should be a Wilkins resistor with a recent traceable calibration certificate maintained at a constant temperature in an oil bath Repeat the procedure for calibrating the 400Q internal reference see section 7 2 2 but Page 58 of 85 CORSE LES Issue 1 01 _ISOT CH configure the microK to measure a Default PRT at 5mA against the internal 10Q reference on the 25Q range with channel The command to adjust the va
4. Format MEASure SCALar VOLTage DC channel gt voltage range Initiates and reports a voltage measurement on lt channel gt using the voltage range specified note that there is no gap between the command and the channel number as this command makes use of the numeric suffices feature of SCPI described in section 10 2 1 This command is equivalent to SENS FUNC volt SENS CHAN channel SENS VOLT RANG voltage range and READ The voltage range specified is rounded up to the nearest available range Example to initiate a voltage measurement on channel 3 using the 0 125V range use MEAS VOLT3 0 125 Page 77 of 85 GRIES Issue 1 01 _ISOT CH 10 4 22 Command MEASure FRES REF Format MEASure SCALar FRESistance lt channel gt REFerence lt reference gt resistance range gt lt current gt Initiates and reports a resistance measurement on lt channel gt against a reference on channel lt reference gt using lt resistance range gt with sense lt current gt note that there is no gap between the command and the channel numbers as this command makes use of the numeric suffices feature of SCPI described in section 10 2 1 This command is equivalent to SENS FUNC fres SENS FRES REF lt reference gt SENS FRES RANG lt resistance range gt lt current gt SENS CHAN lt channel gt and READ Example to set the microK to measure a PRT on channel that has a maximum resistance of 30Q using the internal
5. 3 1 IntroductON 20 3 2 The Startup Window 20 33 The Main WindOW ees sesse ee oe ese Se EG Ge EE EA AG EE RA Ge Ge EE ER AGE GE EE ER AG Ge EE Ee EA Ge Ge GE SR AG Ge Ee Ge 21 3 4 Iura 22 3 5 The Multi TaD eU 24 3 6 Ic 4 26 3 7 The instrument EC on tocos sroo eorn roe ssroror ossos soosse 29 KS IR EE 29 3 7 2 Edit eelere ead es eae ere eh eee Ces 32 31 1 Calibration ena ES Nereis eg Re eee ee hie aes 33 3 74 Restart SolCWare i oir trm ERN PARE IO OE RE OE 33 3 45 Update Software EE oe re ertet etre erae hex er Pe PR e redo ta ere RE no Ev Eat 33 3 7 6 Select Language PP 34 37 1 Changes PassWord ss de a b ETUR RA UL DEOR TO RUE RASA UEM A UR Te a T ERE ARIS 35 3 7 8 EE eelere ee te Nina S 35 327 9 set Date and TIM EE 36 34 10 Backup D3t3 E 36 37A Clear Data ER e 37 3 7 12 Backup Configuration nandi ord e ie oe opu e ED Cr E DR EO DER OR SO EQ dese ee is 37 37 18 bead Contigurafiof nsa eio teh ptt ee ee 37 3 8 Using the Thermometer Database e eeeeeee Gee SE ee GE EE toten nasa s es SR AGE Ge EE GR sess se ses se seen sss Ge sesso 37 3 9 Using the Reference Resistors Database eee eeeee
6. Press the Calibration button to open a Date Entry window and set a recalibration date for your microK The microK will warn you if you attempt to use it past this recalibration date you can disregard the warning and continue to use it but the warning will continue to re appear every hour until the out of calibration issue is resolved 3 7 4 Restart Software Press the Restart Software button to restart the microK software This is useful if you have added or removed microsKanners and want to re invoke the automatic discovery process without cycling the power 3 7 5 Update Software Press the Update Software button to update the software or firmware in your microK The software runs on a 32 bit processor and provides the operator interface The firmware runs on an 8 bit processor and controls the low level hardware in the microK Page 33 of 85 GRIES Issue 1 01 _ISOT CH The new software microk exe or firmware microK version x_xx hex should be located in the root directory of a USB flash drive connected to the front panel USB connector some USB flash drives can take a long time to enumerate in Windows CE and become visible to the software You should therefore wait 15 seconds between plugging in the drive and pressing the button You will be warned that this operation will restart the software press Yes if you wish to continue If the software finds a more recent software or firmware on the flash drive you will be advised of th
7. Measurement Reference Junction Junction The microK supports this arrangement by allowing you to use a temperature measured by another input channel as the reference junction temperature This technique is less accurate than using an ice point or water triple point due to the additional uncertainties associated with the PRT used to monitor the reference junction and any temperature gradients that result in a difference between the temperature of the PRT and the reference junction 4 7 Connecting Thermistors The microK can be connected to thermistors using the same arrangement as for 2 wire PRTs see section 4 4 THERMISTOR Because the resistance of thermistors used for temperature measurement is much higher than for PRTs lead resistance is not normally a problem Use an external reference resistor with thermistors since the resistance of the internal standards is too low Thermistors have much higher temperature coefficients than PRT so the tolerances on the reference resistor are correspondingly less demanding making them relatively inexpensive The top terminal should be connected to the screen of the thermistor s lead to minimise electrical noise picked up by the wires The high resistance of thermistors makes them more prone to picking up electrical noise it is therefore even more important to use a screened cable and connect this to the screen terminal on the microK than when using PRTs Page 43 of 85 GRIES Issue
8. Resistor Reference Guard Amplifier Guarded Measurement System The Guard Amplifier senses the potential at the top of the measurement system and drives the opposite end in order to maintain it at ground potential In this way both the current source and Amplifier see no significant change in voltage common mode signal between the measurements of the Reference Resistor and the SPRT 6 3 Minimising Thermal EMFs Thermal EMFs EMFs generated as the result of junctions between dissimilar metals at different temperatures are a potential source of error when working at this precision These can largely be eliminated when measuring resistance thermometers by reversing the current and averaging the measurements the offsets in the two measurements cancel each other out when the readings are averaged together However this technique cannot be used when measuring temperature with thermocouples so the thermal EMFs need to be eliminated at source For this reason we used tellurium copper gold plated as the connector contact material since this combines good mechanical properties with extremely low thermal EMFs against the copper terminations of a thermocouple Page 49 of 85 CORSE LES Issue 1 01 In order to eliminate thermal EMFs from the measurement system already small the input connections are reversed immediately behind the input terminals Measurements made with and without the reversal are then averaged together
9. Unless you are sure that you do not need any of the files in the internal memory you should transfer all files from the internal memory to a USB flash drive see section 3 7 10 before using this feature 3 7 12Backup Configuration Press Backup Configuration to save the current configuration settings of the microK You will be prompted to enter the password before proceeding You will then be offered the choice buttons of storing the configuration to the Internal DiskOnChip solid state drive memory or an External USB flash drive Press the required button to open an Alpha Numeric Keyboard window and enter a name for the configuration Configurations stored to a USB flash drive are located in directory microKData serialnumber backups where serialnumber is the serial number if the microK This means that you can have duplicate configuration names filenames for measurements provided they apply to different instruments If you want to transfer a configuration from one microK to another you will need to move the configuration file manually on the USB flash drive between the sub directories for the two microKs 3 7 13 Load Configuration Press Load Configuration to load a configuration settings for the microK You will be prompted to enter the password before proceeding You will then be offered the choice buttons of loading the configuration from the Internal DiskOnChip solid state drive memory or an External USB
10. configure the microK to measure a Default PRT at 5mA against the internal 0Q reference on the 25 range on channel 7 1 2 61 O Internal Reference Resistor Connect a stable external resistance standard with a nominal value of to channel Ideally this should be a Wilkins resistor with a recent traceable calibration certificate Configure the microK to measure a Default PRT at OmA against the internal Q reference on the 3Q range on channel other channels disabled Use sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Page 54 of 85 OSE LES Issue 1 01 _ISOT CH Single tab and clear the statistic After the microK has collected at least 100 readings shown as Mean of last in the Single tab check that the Mean agrees with the calibrated value of the resistance standard to within 2 5ppm half of the specification limit of the calibrated value and that the standard deviation S D is less than 0 000005 7 1 3 Voltage Measurements The automatic input reversal of used by the microK when measuring voltage provides good zero stability However small differences between the thermal EMFs generated by the devices used to make these reversals on each channel mean that the zero offset needs to be checked for each channel Once the zeros offsets have been checked adjusted it is only necessary to check the span on one channel since this part of the measurement system is common to all the
11. use SENS RAT RANG 130 1 This will set the microK to the middle range Page 75 of 85 GRIES Issue 1 01 _ISOT CH 10 4 16 Command SENSe RATio RANGe Format SENSe RATio RANGe UPPer Reports the range for the next resistance ratio measurement at the present sense current set using the CURRent command The current used to calculate the range may be different from that specified when the range was set using the SENSe RATio RANGe command The reported range is the actual range for the measurement system at the present sense current Example a microK that has had its resistance ratio range set using the command shown in section 10 4 15 but has its sense current set to OmA would respond to the command SENS RAT RANG with 50 000000 10 4 17 Command INITiate Format INITiate IMMediate ALL Initiates a measurement using the conditions defined by previous SENSe commands The measurement is made immediately but not reported Example to initiate a voltage measurement that has been defined with SENSe commands such as SENS CHAN I SENS FUNC volt and SENS VOLT RANG 0 1 use INIT 10 4 18 Command FETCh Format FETCh SCALar Reports the result of the last measurement made Example a microK that has made a measurement on a short circuit connected to channel using the commands shown in the example in section 10 4 17 will respond to FETC with something similar to 1 70000000E 008 10 4 19 Comm
12. 01 Introduction The microK 250 and micro 500 are the only precision thermometry instruments that can achieve sub mK precision and will work with all three common thermometer sensors PRTs Thermocouples and Thermistors They are based on a completely new measurement technology unique to these products that provides better accuracy and lower noise than comparables technologies see section 6 They are also the first instruments of their type to be completely solid state making them highly reliable Despite their sophistication these instruments are very easy to use There are no knobs and dials just a colour touch screen that makes use of the familiar Windows CE operating system If you use a Windows operating system on your PC you will find these instruments intuitive and easy to use The USB port on the front panel allows you to plug in and use other devices that work with Windows CE such as a mouse keyboard or flash drive Readings can be displayed in resistance ratio ohms volts or temperature units C F or K Algorithms for conversion to temperature include PRTs ITS 90 Callendar Van Dusen IEC75 or custom coefficients Thermocouples IEC584 1 for type B E J K N R S T Type L polynomial Gold Platinum Reference Function Polynomial Thermistor Steinhart Hart This manual provides a comprehensive guide to using the instrument We recognise that you will probably not wish to read it through
13. 100Q reference resistor with a mA sense current use MEAS FRESI REF204 130 1 10 4 23 Command MEASure RAT REF Format MEASure SCALar RATio channel gt REFerence lt reference gt resistance range current Initiates and reports a resistance ratio measurement on channel against a reference on channel reference gt using resistance range with sense current note that there is no gap between the command and the channel numbers as this command makes use of the numeric suffices feature of SCPI described in section 10 2 1 This command is equivalent SENS FUNC rat SENS RAT REF lt reference gt SENS RAT RANG resistance range gt current SENS CHAN channel and READ Example to set the microK to measure the resistance ratio of a PRT on channel that has a maximum resistance of 30 against a 00Q reference resistor on channel 2 with a mA sense current use MEAS RAT I REF2 130 1 10 4 24 Command CURRent Format SOURce CURRent current Set the sense current for the next resistance or ratio measurement to current The current is not changed until a measurement is started using with either the INITiate or READ commands Example to set the sense current for the next resistance measurement to 2mA use CURR 2 Page 78 of 85 GRIES Issue 1 01 _ISOT CH 10 4 25 Command TEST CURRent Format TEST CURRent lt current gt Immediately sets the sense current on channel to lt curre
14. Buttons for V2 and Xx V2 are included to make extrapolation to zero power easier since changing the current in a resistor by a factor of N2 changes the power dissipated by a factor of 2 A PRT s calibration may be defined at a specified current Alternatively it may be specified at zero power In this case you need to determine what the resistance of the PRT would be at zero power This is most easily done by measuring its resistance at the normal sense current and then increasing the current by a factor of V2 and repeating the measurement If you subtract the change in resistance from the first resistance value at nominal current this gives you the resistance of the PRT at zero power Alternatively the second measurement can be made at a current that has been reduced by a factor of V2 In this case the change in resistance should be subtracted from the second resistance value current scaled by V2 to determine the zero power resistance The accuracy of the current source is 0 496 so the uncertainty associated with this extrapolation back to zero power is only 0 896 of the measured resistance change which should be very small Other factors such as the fact that the PRT is not a constant resistance and so the power dissipated has changed between the two measurements are insignificant Samples per Reading box Use the up down buttons to select the number of samples you want to average together to form a single reading Alternatively press the ellip
15. CH _ Isothermal Technology microK 250 S N 14 P702 Firmware v3 21 Loader v1 9 5 Software v1 4 29 Language v1 4 34 microsKanners detected none Resume Measurement system initialised A Resume Pressing the Resume button places the microK in the state it was in prior to its last power down Before pressing Resume make sure that any thermometers attached will not be damaged by the sense currents that will be applied the last values used If there is a problem disconnect your sensors before proceeding and then reconnect them after changing the sense current to the required values 3 3 The Main Window Having pressed Resume in the Startup Window the user is presented with the Main Window Single Multi Settings Instrument Channel of Bia Clear Graph 4 2538 C 4 253776 Mean of last 100 e Start Save Set Scales 9 990168 SD Clear 4 2490000e0 4 2500000e0 4 2510000e0 4 2520000e0 4 2530000e0 4 2540000e0 4 2550000e0 4 2560000e0 4 2570000e0 4 2580000e0 800 850 Time s Page 21 of 85 GRIES Issue 1 01 _ISOT CH All functions to control the microK are available in this Window which is divided into four tabs Single displays a single channel in numeric and graphical form Multi displays all three channels in numeric form Settings allows you to configure the channe
16. Do not apply earth test currents to any front panel terminal nor to the shrouds of the USB RS232 or GPIB connectors The product is designed to comply with EN 61010 1 and can be flash tested It is fitted with radio frequency interference suppressors Therefore it is recommended that only a D C test be performed Performing flash tests repeatedly can damage insulation This equipment contains no user serviceable parts Refer all repairs to qualified service personnel Contact Isothermal Technology or one of our appointed distributors for details of approved service outlets 1 3 Powering Up Your microK The microK operates on any standard AC electrical supply 88 264V RMS at 47 63Hz so unless your supply is unusual you can simply use the power cord provided to connect your microK to a suitable electrical outlet The power switch is located at the rear of the instrument immediately below the IEC connector When you turn your microK on it will go through a standard Windows CE boot sequence and then display a Window containing the Resume button Pressing Resume restarts the microK in the configuration it was in prior to the last power down you will then see the Main Window and be ready to operate your instrument Page 8 of 85 OSE LES Issue 1 01 _ISOT CH A Before pressing the Resume button make sure that any thermometers attached will not be damaged by the sense currents that will be applied the last values used If there is a
17. FRESistance REFerence iese ee ee ee ee ee ee ee ee ee rese 73 10 4 10 Command SENSe FRESistance REFerence ees ee ee ee ee ee ee ee ee ee ee e 74 10 4 1 1 Command SENSe FRESistance RANGe cccececseccccsecccetccceeccctcccsccccnesecesscenseseceucees 74 10 4 12 Command SENSe FRESistance RANGe ii cece ee ee ee ee ee ee ee ee ee ee rese 74 10 4 13 Command SENSe RATio REFerence cccccssecccsececeseccnssccceeccnsscccsscccnseseceecccueseceecees 75 10 4 14 Command SENSe RATio REFerence ccccccssecccssccccsecccesccceeccnsecccscccnsesecescecueseceneees 75 10 4 15 Command SEhSe RATieoRAhtGe nennen enne hene esee hesee esee stresses ee serene sese 75 10 4 16 Command SEhSe RATioRAhtGe eene he see ee rese ee ee sese 76 047 Command INI TIate ce ia is ce ee Nee e ee ee 76 I0 4 18 Command FET CR Ee SE Ee ere be ee Ga ee Ge ee ebay eere Se Gee eg ee Ge Ee GR Gee e eve oe Ee De Ge GR 76 0 4 19 Command READ oo ee ee ee ee ee ee ee ee ee ee ee ee ee ee sese 76 10 4 20 Command READ ee ee ee ee ee ee ee ee rere ssneus 77 Page 4 of 85 ORTI Issue 1 01 _ISOT CH 10 4 21 Command MEASurenV OL T age ei ees epiese eelere ad ve ged Re 77 10 4 22 Command MEASure FRES REF eese nennen nn hee ess sese eene nee essen nnn 78 10 4 23 Command MEASure RAT REF ee ee ee ee ee ese ee ee ee ee ee de ee ee nnn ntes sese sense annees essen nnn 78 104 24 Command CURRents
18. Instrument tab see section 3 7 8 9 2 Establishing a GPIB Connection Connect your microK to a GPIB Controller using a standard straight through GPIB cable Send IDN to the GPIB address of the microK terminated with a Line Feed see section 10 1 for acceptable terminators the microK should then respond with a string in the form Isothermal Technology microK 250 P321 firmmware version 1 24 This confirms that you have successfully established a GPIB connection with your microK Page 65 of 85 GRIES Issue 1 01 _ISOT CH 10 SCPI Command Set The command format and protocol used by the microK is based on the SCPI Standard Commands for Programmable Instruments standard This was developed to provide a consistent command language for all types of programmable instruments The objective was to reduce the development time required by users of these instruments by providing a consistent programming environment through the use of defined messages instrument responses and data formats Further information on SCPI can be obtained from the SCPI Consortium http www scpiconsortium org 10 1 Command Terminators SCPI commands are ASCII American Standard Code for Information Interchange character strings If sent to the microK s RS232 interface these should be terminated with a Carriage Return character ASCII character 13 Responses from the microK on the RS232 interface are always terminated by a Carriage Return character
19. PC through the null modem cable to prevent further data being sent If the PC continues Page 62 of 85 GRIES Issue 1 01 _ISOT CH to send data this will be ignored lost until the microK has had time to make space in the buffer by processing commands The microK does not use its CTS to control data it transmits You can use Hyperterminal or another terminal emulator to communicate with the microK via the RS232 connection Hyperterminal is part of the standard Windows installation usually located in the Accessories Communications folder If you have installed a minimum laptop or custom configuration without this component for your Windows operating system you may need to install Hyperterminal from your original Windows media Start Hyperterminal to setup a new connection Type in a name for the connection such as microK and select an icon In the next window select the PC s COM port to which you have connected your microK from the Connect using drop down list and click OK In the next window enter the data format for the microK s RS232 interface Fa COM14 Properties Je Port Settings Bits per second 9600 vj Data bits 8 KA Parity None vi Stop bits 1 vi Flow control None Ed Restore Defaults Cancel Apply Click OK to open a Hyperterminal session with the microK Now save using File Save As the Hyperterminal connection so that in future you only have to click on t
20. Seconds aximum Minutes 0 038 Autoscale OK Cancel Page 18 of 85 GRIES Issue 1 01 _ISOT CH Press OK to return to the main window The measurement system will now accumulate data and after 5 minutes the graph will begin to scroll to show the last 5 minutes of data Single Multi Settings Instrument Channel 1 Le D LG Clear Graph 0 0300360 0 029468802 0 0360000 0 0340000 0 0320000 0 0300000 0 0280000 0 0260000 0 0240000 0 0220000 0 0200000 00 0180000 ISUT CH Mean of last 100 SC Start Save set scares 0 000622726 SD Clear EE IBERIA ea 250 300 350 400 450 500 Times Page 19 of 85 Issue 1 01 _ISOT CH 3 Driving Your microK 3 1 Introduction The operator interface for the microK is provided through the touch screen and colour display The software is written in Microsoft s new C language and runs under the Windows CE operating system This provides a familiar and easy to use interface The buttons in the microK software have been sized and positioned to allow you to operate the instrument with your finger If numeric or alphanumeric data needs to be entered a soft keyboard window appears If you are unfamiliar with touch screen devices such as PDAs you may initially feel that the touch screen interface is slow compared with using a mouse
21. a Numeric keypad window and enter the required value Press OK to save the changes and close the window Press Cancel to close the window without making any changes 3 7 0Backup Data Press Backup Data to transfer data that has been saved to the internal memory see section 3 4 or 3 5 to an external USB Flash Drive You need to plug a USB Flash Drive into the front of the microK in order to use this facility With some Flash Drives it can take up to 15 seconds for these to enumerate and therefore be recognised by the Windows CE operating system you therefore need to wait for 15s after plugging in the USB Flash Drive before attempting to transfer the data otherwise a No external drive present warning will appear If a file with the same name is already present on the USB flash drive you will be asked whether you wish to over write it To proceed you will need to enter the password Files are transferred to the USB flash drive in directory microKData serialnumber data where serialnumber is the serial number of the microK used to make the measurements This means that you can have duplicate filenames for measurements provided they are made with different instruments Page 36 of 85 GRIES Issue 1 01 3 7 11 Clear Data Files Press Clear Data Files to delete the data files from the internal memory this frees up space for new files to be recorded You will be prompted to enter the password before proceeding
22. and keyboard but with a little practice you should quickly become comfortable with the technology and appreciate its benefits However if you prefer to use a USB mouse or keyboard you can simply plug these into the USB connector on the front panel They will immediately become active provided they use the standard class drivers built into the Windows CE operating system used in the microK To use more than one USB device simply plug a USB hub into the front panel connector Calibration data entered into the microK s database is password protected and includes recalibration dates the microK will alert you if you try to use a thermometer or reference resistor after its recalibration date This feature ensures the integrity of your measurements and helps you to comply with the requirements of accreditation bodies 3 2 The Startup Window When power is applied to the microK it goes through a Windows CE boot sequence that loads the operating system and then starts the microK application The Startup Window then appears showing the microK s model and serial number together with the version numbers for the measurement system firmware and microK software used The window also lists the details of any microsKanner multiplexers connected to the microK the microsKanner manual describes how to use microsKanner multiplexers with your microK bridge The Startup Window contains the Resume button Page 20 of 85 GRIES Issue 1 01 _ISOT
23. channels 7 1 3 1 Zero Voltage Offsets Short out the 4 measurement terminals on all 3 channels using a piece of un insulated copper wire use pure copper wire to avoid generating unwanted thermal EMFs for each channel V I Configure the microK to measure a Default Thermocouple on the 0 125V range with units of Volts Use sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Multi tab and clear the statistics for all 3 channels After the microK has collected at least 100 readings shown as Mean of last in the Multi tab check that the Mean for each channels is less than 0 000000250 0 254 V and that the standard deviation S D is less than 0 000000050 0 05UV 7 1 3 2Voltage Span Check Connect a stable low noise voltage source with a nominal value of 50mV to channel of the microK using low thermal EMF wire and connectors copper or an alloy such as tellurium copper that has a high copper content and low thermal EMF to pure copper Brass connectors must NOT be used Page 55 of 85 GRIES Issue 1 01 Voltage V l Source Oo Configure the microK to measure a Default Thermocouple on the 0 125V range with units of Volts Use sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Single tab and clear the statistics After the microK has collected at least 100 readings shown as Mean of last in the Single tab check that the Mean value agrees with t
24. create edit delete a thermometer database entry create edit delete a reference resistors database entry backup internal data to a USB flash drive overwrite a data file on the USB flash drive delete internal data files backup a configuration load a configuration change the password upgrade the software EE S S EE EO Ge Gs Ge EE Page 39 of 85 GRIES Issue 1 01 _ISOT CH 4 Connecting Thermometer Sensors 4 1 The Cable Pod Connectors The Eichmann Cable Pod connectors used on the microK have gold plated tellurium copper contacts These generate exceptionally low thermal EMFs when connected to the copper terminations used on standards grade thermocouples The connectors accept 4mm plugs bare wires or spade terminations Additionally they are spaced on 19mm 74 pitch so that they can be used with standard 4mm to BNC adaptors not supplied for connecting to BNC terminated SPRTs The mechanism is designed so that the clamping surface does not rotate as it clamps the wire in order to avoid damaging it A The Cable Pod mechanism is made from a high strength polymer but nonetheless may be subject to mechanical damage if the connectors are over tightened Please tighten the terminals to a light finger tight level in order to ensure that they are not subject to undue wear or premature failure This is all that is required electrically do not try to use the connector to provide strain relief or te
25. eee e RA Ge Ge senes teen tasa sese s sete esas sa se sese ER assa ses sese soo 38 3 10 Saving Instrument Configurations eee e esee eee ES SE tna sanas SR nasa sa sese SR AG Ge ses sesso ss sa ses ee Ge 39 3 11 Password Protection of Key Settings eee eee eiie eee eese ette Ge EE sete RA Ge Ge EE SR assa se sese RA Ge Ge sese soo 39 Page 2 of 85 GRIES Issue 1 01 _ISOT CH 4 CONNECTING THERMOMETER SENSORS 40 4 1 The Cable Pod ConnectorS 40 4 2 Connecting PRTs 4 wire sesse sees oe ese se ee GE ES SR AG Ge EE ER AG Ge EE ER AG GE GR AG Ge EE EA Ge Ge ES Se ee Ge ee 40 4 3 Connecting PRTs 3 wire esse sees oe ese Se AG Ge EE SR AG Ge EE SR AG Ge EE SR AG Ge EE EG AA Ge GE SA Ge Ge EE Se Ee ee ee 4l 4 4 Connecting PRTs 2 wire sesse sees sesse SR ee Ge ES SR AG GE EE SR AG Ge EE SR AG GE Ee AG Ge EE EA Re Ge EE Se Ee Ge ee al 4 5 Connecting Thermocouples external Ice Point or WIP susse sesse sesse ee Ge EE SS RA Ge Ge EE SR AG Ge ee Ge 42 4 6 Connecting Thermocouples using RJ compensation ssscccscccsssssssssssssscessssscsssscessessssscssssseseesscsscsess 42 4 7 Connecting Thermistors 43 5 GOOD PRACTICE GUIDELINES ccccccccccccccccccccscscccscseeene 44 5 1 Looking After Your micro 44 5 2 Making a Goo
26. flash drive Press the required button and then use the up down buttons to select the required configuration Press OK to load the configuration or press Cancel to close the Window without loading the configuration 3 8 Using the Thermometer Database The microK contains a database that allows you to enter review and edit information about the thermometers you use You can then select a thermometer from this database and all the parameters associated with it will be loaded and used by the measurement system This means that you do not need to enter information such as the calibration coefficients each time you use the thermometer and therefore avoids the associated risk of data entry errors The database also allows you to enter calibration due dates to ensure that you do not unwittingly use devices beyond their recalibration date The microK will warn you if you attempt to use a thermometer Page 37 of 85 OSE LES Issue 1 01 _ISOT CH past its recalibration date you can disregard the warning and continue to use the thermometer but the warning will continue to re appear every hour until the out of calibration issue is resolved Enter data on the thermometers you use as reference standards or measurement devices into the microK s database see section 3 7 1 You can then use one of these thermometers by selecting it in the Thermometer box in the Settings tab see section 3 6 The database allows you to enter information about the
27. in the Multi tab shows whether readings are being recorded to a file The measurements are written to the file in comma delimited ASCII text form allowing easy importation into Microsoft Excel or other applications Page 25 of 85 GRIES Issue 1 01 _ISOT CH 3 6 The Settings Tab Select this tab to configure each channel for the required measurements Single Multi Settings Instrument Channel Units IL T Q Disable 17 Ohms IL Thermometer Current mA t Default PRT nl Komme Conversion Samples per Reading None D ft iit n m Range Ohms Readings in Rolling Statistics t 125 D ff 100 Di Reference Channel Reference Resistor f Internal 100R Il vie 100 J Channel box Use the up down buttons to select the channel you wish to configure Alternatively press the ellipses button to open a numeric entry window and select the channel directly The ellipses button is particularly useful when the microK is used with microsKanner multiplexers which can provide up to 90 expansion channels Enable Disable button Use this button to enable or disable a channel Disable unused channels to skip measurements on that channel and reduce the cycle time through the channels The nearby indicator shows whether the currently selected channel is enabled Thermometer box Use the up down butto
28. lint free cloth The rest of the microK should not require cleaning as often as the display and can be cleaned in the same way as the screen Never use abrasive cleaners such as cream cleaners on your microK 5 2 Making a Good Electrical Measurement Although the microK is intended for use in temperature metrology its base measurements are electrical resistance or voltage The limited sensitivity of PRTs and thermocouples means that in order to achieve uncertainties at the mK level we need to make electrical measurements that rival those of a good electrical metrology laboratory For example for a 25O SPRT a ImK temperature uncertainty corresponds to 1004 O0 resistance uncertainty With a mA sense current this corresponds to a voltage uncertainty of 0 uV The microK has been optimised for electromagnetic compatibility minimising emissions and maximising immunity However since the microK is capable of measuring to such low signal levels it is worthwhile adopting good electrical measurement practices Here are a few guidelines Page 44 of 85 GRIES Issue 1 01 _ISOT CH The most sensitive points are the inputs to the microK measuring to better than 0 UV Whilst the microK will work satisfactorily with just a four wire connection to the PRT or reference resistor using the voltage sense and current terminals marked V and I respectively it is better to use a screened cable and to connect the screen to the me
29. microK uses a substitution technique in which the Device Under Test and the Reference are successively switched into the same position in the measuring circuit This means that the stability of resistance ratio measurements is immeasurably small see section 6 2 ISUT CH Page 83 of 85 Issue 1 01 _ISOT CH 12 Approvals The microK has been independently verified as complying with the regulatory requirements of the EU and FCC for electromagnetic compatibility and safety EU only 12 1 CE Declaration C European Community Electromagnetic Compatibility Directive 89 336 European Community Low Voltage Directive 93 68 The microK Precision Thermometry Bridge manufactured by Isothermal Technology Limited of Pine Grove Southport Merseyside PR9 9AG United Kingdom conforms to the requirements of the European Community Electromagnetic Compatibility Directive 89 336 and of the European Community Low Voltage Directive 93 68 12 2 FCC Statement This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to part 15 of the FCC Rules These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment This equipment generates and can radiate radio frequency energy and if not installed and used in accordance with the instruction manual may cause harmful interference to radio communications Operation
30. of this equipment in a residential area may cause harmful interference in which case the user will be required to correct the interference at his own expense Changes or modifications to this equipment not expressly approved by Isothermal Technology could degrade EMC performance and void the user s authority to operate the equipment 12 3 Standards Applied The following standards have been applied in assessing compatibility with the requirements for CE marking and for FCC compliance Conducted Emissions EN6 1326 1997 amp CFR47 2005 Radiated Emissions EN6 1326 1997 amp CFR47 2005 Conducted Immunity EN6 1326 1997 Radiated Immunity EN6 1326 1997 Electrical Fast Transients EN6 1326 1997 Electrostatic Discharge EN6 1326 1997 Surge EN6 1326 1997 Voltage Dips amp Interruptions EN6 1326 1997 Harmonic Currents ENG 1000 3 2 2000 Flicker ENG 1000 3 3 1995 Electrical Safety EN61010 1 2001 Page 84 of 85 GRIES Issue 1 01 _ISOT CH 13 Revision History Change Note Date Manual Issue Initial release 12 12 201 1 00 CNI4001 20 01 2014 1 01 Page 85 of 85 ISUT CH Issue 1 01
31. problem disconnect your sensors before proceeding and then reconnect them after changing the sense current to the required values 1 4 A Quick Tour of Your microK On the front panel of your microK you will find the input terminals for the three measurement channels the touch screen colour display and a USB connector Page 9 of 85 GRIES Issue 1 01 en en oe LoF 08 Input USB Terminals Connector Touch Screen amp Display Input Terminals The input terminals accept 4mm plugs spades or bare wires The current I and voltage sense V terminals are spaced on 3 centres so that standard BNC to 4mm adaptors not supplied can be used to connect to thermometer sensors that have BNC terminations The contact material for the connectors is gold plated tellurium copper offering extremely low thermal EMFs when connected to copper wires connectors This is essential when using precision thermocouples Display The display is a colour TFT VGA 640 x 480 LCD with a long life CCFL cold cathode fluorescent lamp backlight A touch panel is mounted in front of the display so that you can control the instrument by simply touching the buttons displayed on the LCD The touch panel is an industrial grade components offering good durability It is intended to be operated with a finger A stylus intended for PDAs may also be used never use a sharp object with the touch panel as this will lead to premat
32. readings are taken The time between readings depends on the settings for that channel and any other channels that are also enabled This can vary between 2 seconds and 5 minutes The measurement time for a PRT or thermistor is 2s and for a thermocouple it is lt Is The reading rate for three PRTs with one sample per reading will therefore be 6s Start Save Press the Start Save button to record all the measurements being made You will then be offered the choice buttons of storing the data to the Internal DiskOnChip solid state drive memory or an External USB Flash Drive Data stored to the internal memory can subsequently be transferred to an external USB Flash Drive using the Backup Data button on the Instrument tab see section 3 7 10 The internal memory used has a capacity to at least 32Mbytes this will accommodate approximately 1 300 000 PRT readings or about 30 days of continuous logging at the fastest rate Select the destination for the data to open an Alpha Numeric Keyboard window and enter a filename An automatically incrementing default name will appear in the entry box press OK to accept this or use the backspace and alpha numeric keys to enter your preferred filename If you try to use a filename that has already been used you will have to enter the password to proceed see section 3 1 for details on password protection The Shift key toggles the alpha keys between upper and lower case The indicator by the Start Save button
33. settings Page 17 of 85 GRIES Issue 1 01 Ecc Single Multi Settings Instrument Channel Units Eds es Thermometer Default Thermocouple n 7 Conversion Samples per Reading Type N Thermocouple IL f it n E iV Readings in Rolling Statistics x is zl Reference Junction D 0 00 C 4 The reference junction is assumed to be an ice point in this tutorial It can be set to the water triple point or e e 2 zm D a D to use a temperature measured by one of the other channels see sections 3 6 and 4 6 if using reference junction compensation Connect the N type thermocouple to channel see section 4 5 for details on how to connect thermocouples Press the Single tab to see the measurements in numeric and graphical form Set the graph scales manually by making a note of the current Mean value and pressing Set Scales This opens the graph scales window Ensure that autoscaling is turned off press Autoscale to toggle autoscaling on off the status of autoscaling is shown by the adjacent indicator Use the ellipses buttons to set the y axis limits to be 0 01 C above and below the current mean value Use the radio and up down buttons to set the x axis to 5 minutes Y Axis X Axis Channel Scale Minutes sj CEEA inimum Time Units 0 018 A O
34. the changes and close the Window 3 7 2 Edit Resistors Press the Edit Resistors button to create edit or delete a reference resistor in the database You will be prompted to enter the password in order to proceed tt WILKINS 25 N Resistor Resistor Name Value WILKINS 25 e 24 98765 e Manufacturer s Name Tinsley Serial Number W151256 as Calibration Due 30 10 2010 Zeg New Delete OK Resistor box Use the up down buttons to select the reference resistor you wish to edit or delete Alternatively press the New key to create a new reference resistor entry The internal reference resistors are included in the list but cannot be edited or deleted Resistor Name box This box contains the name of the selected reference resistor If you are creating a new reference resistor entry the ellipses button by the box becomes active Press this button to open an Alpha Numeric Keyboard window and enter a name The Shift key toggles the alpha keys between upper and lower case Manufacturer s Name box This box contains the manufacturer of the selected reference resistor If you are creating a new reference resistor entry the ellipses button by the box becomes active Press this button to open an Alpha Numeric Keyboard window and enter a name The Shift key toggles the alpha keys between upper and lower case Serial Number box This box contains the serial num
35. thermometer Thermometer Name the name you use to refer to the thermometer Manufacturer s name Serial Number Calibration Due date Thermometer Type Minimum Temperature operating Maximum Temperature operating Conversion algorithm for converting base reading to temperature EE S S HL EE EE Gs EE Information in the database is password protected to help you comply with the reguirements of accreditation bodies 3 9 Using the Reference Resistors Database The microK contains a database that allows you to enter review and edit information about the reference resistors you use You can then select a reference resistor from this database and all the parameters associated with it will be loaded and used by the measurement system This means that you do not need to enter its value each time you use it and therefore avoids the associated risk of data entry errors The database also allows you to enter calibration due dates to ensure that you do not unwittingly use devices beyond their calibration interval The microK will warn you if you attempt to use a reference resistor past its recalibration date you can disregard the warning and continue to use it but the warning will continue to re appear every hour until the out of calibration issue is resolved Enter data on the reference resistors you use with your resistance thermometers into the microK s database see section 3 7 2 You can then use one of these reference resistors us
36. 1 01 _ISOT CH 5 Good Practice Guidelines 5 1 Looking After Your microK Your microK is a precision electronic instrument intended for indoor use in a laboratory or office environment Nonetheless it has been designed to be as robust as practical and will provide many years of service provided it is properly maintained We recommend that you return your microK to Isothermal Technology or one of our approved service centres on an annual basis for calibration Isothermal Technology has developed a calibration kit for the microK Contact Isothermal Technology or one of our appointed distributors if you wish to purchase a kit to calibrate the microK yourself The microK should require little maintenance between calibrations other than routine cleaning Under no circumstances should you use sharp or unsuitable objects such as ball point pens on the touch screen as this will lead to premature failure It is also a good idea to ensure that you have clean hands when using the touch screen You should ensure that you do not have contaminants such as adhesives or solvents on you fingers when touching the screen as these will be difficult to remove without damaging the screen The touch screen can be cleaned with a damp not wet cloth Use either a proprietary screen cleaner suitable for PC flat panel displays or water and a little mild liquid soap on a lint free cloth to wipe the touch screen Dry the screen immediately after cleaning with a
37. C resolution However the reduced differential gain inherent in the higher resolution DAC greatly improves loop stability too This allows the use of more orders of integration and higher loop gain giving a disproportionate improvement in quantisation noise With the 5 bit system used in the microK the quantisation noise is reduced by a factor of 600 so that the performance of the microK is not limited by the X A ADC technique but by the electronic devices used in the ADC and the rest of the measurement system Another benefit of the new ADC is its speed The implementation used in the microK provides conversions to full accuracy in 0Oms This together with the use of solid state switching allows for a very fast reversal Page 47 of 85 GRIES Issue 1 01 _ISOT CH rate which in turn helps to eliminate the effect of any thermal EMFs and reduce the noise since the system can operate above the corner frequency of the amplifiers f noise 6 2 Substitution Topology In conventional potentiometric instruments a common DC current is passed through a thermometer Rx and reference resistor R A voltmeter is switched between reading the voltage across Rx and R and the ratio of the two readings n is calculated Amplifier Conventional Potentiometric Resistance Measurement A significant source of error with this measurement topology is the common mode rejection ratio of the input amplifier The common mode signal at the input
38. Coefficients for T gt 0 01 C a 0 D a 0 00029667298 p 10 s b 2 3806071e 05 c 3 0497121e 06 d 0 CC Press OK to close the coefficients window and press OK again to close the thermometer database window Press the Settings tab in the main window and disable channels 2 and 3 this will speed up measurements on channel which we will be using by using the up down buttons by the Channel box to select these channels and pressing Disable Use the up down buttons to return to channel Use the up down or ellipses buttons by each box to select the required settings Page 14 of 85 GRIES Issue 1 01 Single Multi Settings Instrument Channel ks ef am GE Thermometer Current mA DN SPRT1 D bs 1 0000 Conversion Samples per Reading Es Blos Range Ohms Readings in Rolling Statistics D 125 al D 100 al kel Reference Channel Reference Resistor D Internal 100R al LG D 100 D B The sense current is assumed to be mA in this tutorial It can be set to other values using the ellipses button by the Current mA box see section 3 6 Connect the SPRT to channel see section 4 2 for details on how to connect 4 wire PRTs The tutorial assumes you are using the internal 00Q reference resistor To use an external reference resistor first enter information on the re
39. Mean of last in the Multi tab record the Mean for each channel and check that the standard deviation S D is less that 0 000000050 0 05y V Now adjust the zero offsets using the commands CAL OFFSI offset CAL OFFS2 offset2 CAL OFFS3 offset3 Where offsetX is the zero offset measured for channel X The value entered for each channel can be read back using CAL OFFSX for channel X Re check the zero offsets for all three channels see section 7 1 3 1 7 2 8 Calibrating Voltage Span Connect a stable low noise voltage source with a nominal value of 50mV to channel of the microK using low thermal EMF wire and connectors copper or an alloy such as tellurium copper that has a high copper content and low thermal EMF to pure copper Brass connectors must NOT be used Voltage V l Source Oo Configure the microK to measure a Default Thermocouple on the 0 125V range with units of Volts Use sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Single tab and clear the statistics After the microK has collected at least 100 readings shown as Mean of last in the Single tab record the Mean value and check that the standard deviation S D is less than 0 000000050V 0 05UV Calculate the require gain from actual value gain measured value Now apply the new gain by typing the command CAL GAIN X40 POS gain Page 60 of 85 GRIES Issue 1 01 _ISOT CH The value ente
40. N Attention 23 GND Ground paired with ATN 12 GND Shield 24 GND Logic Ground Shell Frame Ground cable screen Unlike the RS232 interface which is full duplex the GPIB is inherently half duplex data can only be transferred between the microK and the GPIB Controller in one direction at any given time this direction being determined by the controller If a response is expected from the microK the GPIB Controller must address the microK as a Talker in order that it can transmit this information The microK will try to send information on the GPIB for 2s after which time it will abandon attempts to respond and revert to being a Listener in order to received further commands on the GPIB This 2s window will start as soon as the microK is ready to respond There will be a delay from receiving the command to attempting to respond depending on the command requesting data involves a short delay but requesting a measurement may take up to 2s and whether the microK is busy processing other commands if measurements are being requested via the front panel operator interface or via the RS232 interface The microK has a 254 byte receive buffer If the command exceeds this length it will be truncated Page 64 of 85 GRIES Issue 1 01 _ISOT CH 9 1 GPIB Address The microK behaves as a GPIB Peripheral and can have an address in the range to 30 inclusive The factory default address is 10 but this can be changed pressing Port Settings in the
41. NSe CHANnel channel Selects the channel for the next measurement The channel is not actually selected until a measurement is started using with either the INITiate or READ commands Example to select channel 2 for the next measurement use SENS CHAN 2 Page 72 of 85 GRIES Issue 1 01 _ISOT CH 10 4 6Command SENSe CHANnel Format SENSe CHANnel Reports the channel selected for the next measurement Example a microK set to measure channel on the next measurement will respond to SENS CHAN with 10 4 7Command SENSe VOLTage RANGe Format SENSe DC VOLTage RANGe UPPER lt voltage range gt Sets the range for the next voltage measurement There are 3 voltage ranges available in the microK H 0 0 125V 0 0 5V 0 2 5V If you enter a numeric value other than one of the above the microK will round the value up to the next available range Always use the most sensitive range possible to minimise uncertainties Therefore when measuring thermocouples always use the 0 125V range Example to set the microK to measure a thermocouple that has a maximum output voltage of 20mV use SENS VOLT RANG 20mV This will set the microK to the 25mV range 10 4 8Command SENSe VOLTage RANGe Format SENSe DC VOLTage RANGe UPPER Reports the range for the next voltage measurement 0 125 0 5 or 2 5 Example a microK that has had its voltage range set using the command shown in section 10 4 7 would res
42. SCPI commands you can stop all measurements requested via the front panel operator interface The easiest way to do this is to restart the microK and then not press Resume in the opening window The main application that provides the user interface will then not start and no measurements will be requested 10 3 1 Measuring Resistance using SCPI Commands In order to measure the resistance of a PRT you need to set the microK to measure resistance set the sense current select the measurement range select the measurement channel select the reference channel make the measurement EE PO HP Gs Gs EE If you want to measure a 25 5Q SPRT up to a maximum resistance of 30Q against the internal 00Q reference the maximum resistance that the measurement system sees is 100 To make this measurement using a mA sense current you can use the following command sequence SENS FUNC FRES CURR SENS FRES RANG 100 SENS CHAN SENS FRES REF 204 READ The microK will then report the measured resistance for example 2 5250637862E001 Page 69 of 85 GRIES Issue 1 01 _ISOT CH The following command performs the same measurement MEAS FRESI REF204 100 10 3 2Measuring Voltage using SCPI Commands In order to measure the voltage from a thermocouple you need to set the microK to measure voltage select the measurement range select the measurement channel l make the measurement If you want to measure the vol
43. a voltage gain for positive readings on its x40 range that is low by a factor of 1 000123 see section 7 2 8 the gain can be corrected using CAL GAIN X40 POS 1 000123 Page 80 of 85 GRIES Issue 1 01 _ISOT CH 10 4 32 Command CALibrate GAIN Format CALibrate GAIN lt gain gt lt polarity gt Reports the total calibration adjustment applied to the voltage lt gain gt range The parameter lt gain gt must be one of three strings defining the nominal gain of the microK pre amplifier jx XIO X40 The parameter lt polarity gt must be either POSitive or NEGative Example a microk that has had a number of adjustments to its nominal x40 gain causing a total ratio adjustment of 1 000123 for positive readings will respond to CAL GAIN X40 POS with 1 000123 10 4 33 Command CALibrate PASSword Format CALibrate PASSword old password password gt password Changes the password used to lock protect the calibration of the microK s measurement system This is initially set to 1234 but should be changed before using the microK for any critical or traceable measurement or calibration work The new password must be at least 4 characters in length and must be typed in identically twice in order to effect the change Example to change the password from 1234 to ABCD use CAL PASS 234 ABCD ABCD 10 4 34 Command CALibrate UNLock Format CALibrate UNLock password Unlocks the microK to allow calib
44. and READ Format READ SCALar Initiates and reports a measurement using the conditions defined by previous SENSe commands This is equivalent to INIT followed by FETCh Page 76 of 85 GRIES Issue 1 01 _ISOT CH Example a microK that is connected to a short circuit on channel and has been configured to make a voltage measurement using SENSe commands such as SENS CHAN I SENS FUNC volt and SENS VOLT RANG 0 1 will respond to READ with something similar to 1 70000000E 008 10 4 20 Command READ Format READ lt channel gt Reports the next measurement and units on channel gt made using the front panel operator interface It is the only command that allows the user to access results in temperature units Unlike other commands where it is recommended that the operator interface is left dormant Resume not pressed to speed up measurements the operator interface MUST be running measurements being made in order for this command to function Example a user who is making temperature measurements on channel using an SPRT see section 2 1 can read the temperature measurements by sending READ I The microK will respond with something similar to 1 23456789 C The units are reported using X Ratio R Ohms V Volts K Kelvin C Celsius F Fahrenheit If the requested channel does not exist or is not enabled the microK will respond with not enabled X 10 4 21 Command MEASure VOLTage
45. apability of the micro to eliminate the effect of lead resistance completely In this arrangement the current and voltage sense connections are kept separate and are only joined close to the PRT Page 41 of 85 GRIES Issue 1 01 _ISOT CH 1 PRT The top terminal should be connected to the screen of the PRT s lead to minimise electrical noise picked up by the wires 4 5 Connecting Thermocouples external Ice Point or WTP The microK s measurement system uses active guarding As a result the voltage measurement system is floating until it is connected to the sense current terminals In order to measure the voltage on a thermocouple the two current terminals should be connected to each other and to the red voltage sense terminal Thermocouple Measurement Reference Junction Junction The most accurate thermocouple measurements are made with the reference junction immersed in an ice point bath or water triple point The microK supports this arrangement by allowing you to specify the temperature of the reference junction as 0 C or 0 01 C see section 3 6 4 6 Connecting Thermocouples using RJ compensation It is possible to measure the temperature of the reference junction and compensate for the associated EMF at this junction The reference junction can be measured using a PRT or thermistor connected to another measurement channel Page 42 of 85 GRIES Issue 1 01 _ISOT CH Thermocouple
46. asurement ground terminal above the input terminals Screen Measurement Ground Terminal TT gt LI U Reference Resistor The screen should also be connected to the outer sheath of the SPRT if it is metal clad or the case of the reference resistor The use of screened cables is more important when the microK is used with thermistors which have a higher resistance than PRTs or thermocouples Keep the cables to the microK input terminals away from other cables that might be sources of electrical noise for example electrical supplies to furnaces The insulation in high temperature furnaces any that glow begins to conduct at higher temperatures This can cause high common mode voltages on any thermometer in the furnace Whilst the microK is designed to reject common mode DC and AC signals at both 50 and 60H72 it is good practice to minimise them It is common practice to use a metal equalising block in a furnace when performing comparison calibrations This should be connected to the safety earth of the electrical supply most furnaces designed for temperature metrology applications are fitted with a device to earth the equalising block Do not earth the equalising block to the screen measurement ground terminals on the front panel of your microK as this is not connected to the safety earth of the electrical supply Provide a clean electrical environment in your temperature laboratory It may be useful
47. at this time so suggest you read the safety section below take one of the tutorials in section 2 and then refer back to the manual using the list of contents to find additional information as required Page 6 of 85 GRIES Issue 1 01 _ISOT CH I 1 Unpacking Your microK product should comprise the following items microK precision thermometer power lead suitable for your country this user manual If any item is missing or damaged please report this immediately to your supplier If possible we recommend that you retain the packaging material in case you need to return the instrument for calibration or service since it has been designed to ensure that your microK is properly protected during transportation 1 2 Safety The microK is a precision instrument designed for use in a laboratory It complies with the requirements of safety standard EN61010 1 2001 and is therefore safe to use in laboratory or light industrial environments It is not intended for use outdoors or in extreme environments refer to specification in Section 1 A The microK is likely to be connected to thermometer sensors in use and the operator should take care to ensure that the complete system is safe For example metal sheathed thermometers may be connected to the microK and then placed in a furnace powered from a 230V electrical supply Single fault conditions in such a furnace could lead to the thermometer wires and therefore the front termi
48. ave Set Scales 4 2538 aC 4 253776 0 000168 Mean of last 100 SD Clear 850 Times 2 2 Measuring Temperature with a Thermocouple From startup press Resume to restart your microK fj ISUT CH Page 16 of 85 Issue 1 01 Isothermal Technology microK 250 S N 14 P702 Firmware v3 21 Loader v1 9 5 Software v1 4 29 Language v1 4 34 microsKanners detected none Resume Measurement system initialised This tutorial describes the use of an uncalibrated type N thermocouple The microK can be used with calibrated thermocouples in which case you will need to enter information about the thermometer into the microK s database and see section 3 7 1 and select this thermometer entry from the Thermometer box in the Settings tab see later in this tutorial When the main window opens press the Settings tab Singl Chan DI Er i Clear Graph Rt Rs L Mean Start Save Set Scales SD rem Settings Instrument m o Dr Mu kO TDN o o o 0 0 Time s In the Settings tab disable channels 2 and 3 this will speed up measurements on channel which we will be using by using the up down buttons by the Channel box to select these channels and pressing Disable Use the up down buttons to return to channel Use the up down buttons by each box to select the required
49. ber of the selected reference resistor If you are creating a new reference resistor entry the ellipses button by the box becomes active Press this button to Page 32 of 85 GRIES Issue 1 01 _ISOT CH open an Alpha Numeric Keyboard window and enter a serial number The Shift key toggles the alpha keys between upper and lower case Calibration Due box This box contains the date when calibration is due for the selected reference resistor If you are creating a new reference resistor entry the ellipses button by the box becomes active Press this button to open a Date Entry window and enter a date The ellipses buttons by the Day Month and Year boxes in the Date Entry window open a Numeric Keypad window Dates are checked for validity including leap years for dates up to 31 December 2099 Value box This box contains the calibrated value for the selected reference resistor If you are creating a new reference resistor entry press the ellipses button to open a Numeric Keypad window and enter the calibrated resistance value in ohms New button Press this button to make a new thermometer entry into the microK s database ellipses and up down buttons by the boxes then become active Delete button Press this button to delete the selected reference resistor or the current entry for a new reference resistor from the database OK button Press this button to confirm the changes and close the Window 3 7 3 Calibration
50. bration e x Edit thermometers Port Settings Edit Resistors Set Date and Time Calibration Backup Data Restart Software Clear Data Files Update Software Change Password Select Language Load Configuration Backup Configuration You will be prompted to enter the password set to 1234 initially but this should be changed before using the microK in a real measurement calibration application to ensure security see section 3 7 6 Enter the password to open the thermometer database window Press New to create a new thermometer entry in the database and enter data by pressing the up down or ellipses buttons by each field Page 13 of 85 GRIES Issue 1 01 fr ISPRTL D Thermometer Thermometer Name Thermometer Type SPRT1 t IPRT Manufacturer s Name in Temperature C 0 00 Isothermal Technology Serial Number lax Temperature C 66032 123 660 00 Conversion Delete Coefficients 15 12 2010 is EL EL GS Calibration Due g Press Coefficients to open the coefficients window Press the ellipses buttons to enter the calibration data for the thermometer from its calibration certificate Conversion Name Conversion Type ITS90 A ITS 90 R001 25 4321 Le Coefficients for T lt 0 01 C
51. channels These replace the sense current when a channel is not being measured and ensure that the power dissipated in an SPRT remains constant The most accurate measurements with an SPRT involve measuring its resistance at two sense currents and then extrapolating back to the zero power value The microK s user interface provides a simple feature to allow the sense current to be scaled by a factor of root two a factor of 2 in power to make this technique easy for the user to implement see section 3 6 Page 51 of 85 GRIES Issue 1 01 _ISOT CH 7 Calibration The ADC and measurement topology used in the microK are inherently very stable with both time and temperature The stability of the microK is primarily determined by its internal standards a zener reference for voltage and bulk metal foil resistors for resistance We have used the best available components for these internal standards a Linear Technology precision zener reference of the type used for voltage transfer standards in electrical metrology and Vishay hermetically sealed bulk metal foil resistors To keep your microK operating within its performance specification it should be recalibrated annually Please contact Isothermal technology to arrange this calibration 7 1 Checking Calibration The calibration can be checked by measuring known standards with the microK The calibration should be performed in a temperature controlled environment between 19 C and 25 C T
52. d Electrical Measurement scccccscssssssssscsccsscssssssssscesesscsssssseceessessesscseceseesscsscssosesesseesoonns 44 6 THE MICROK TECHNOLOGY cccccccscssccsssssscscccccccccssecsccessese FO 6 1 Ne S EE EE EE EE OE OE EE 46 6 2 Substitution Topology 48 6 3 Minimising Thermal wl CT 49 6 4 Solid State Switching 50 6 5 Inherent Stability ee 50 6 6 Eliminating Self Heating Effects susse esse esse sesse ee oe eee SS Re Ge Ge EE SR AG Ge ses SE Re Ge Ge SA AG ses SR AGE sese sese tnon 51 7 1 Checking Calibration 52 7 1 1 Checking the Master Current Source EEN 52 7 1 2 Resistance Measurements n nnn nne es sss snn eene sees esse anna enne eese ea 53 1 1 2 1 Zero Ohms Che k AS oce eee eerte rn eee er Ra Te Ee 53 7 1 2 2 400 Q Internal Reference Resistor ees ee ee ee de ee nemen nnn nennen ns 54 7 1 2 3 100 Q Internal Reference Resistor cccccssceseccccccccescesssececcssceeeuseseseeeccssseesueuenseeeesess 54 7 1 2 4 25 Q Internal Reference Resistor cccccccesseseccccsceesecesseeeeccssseeeueessseseccssseeuuuenseseeeeess 54 7 1 2 5 lO Q Internal Reference Resistor ccccccssssececcccceeeecesseeeeccssseeeueuseseeeccssseeeueunseeeeecess 54 7 1 2 6 Q Internal Reference Resistor cccccsss
53. e version levels and offered the opportunity to update to the later version you will also be prompted to enter the password before proceeding If the flash drive does not contain a more recent version the software will simply restart If you are updating the firmware you will need to cycle the power to the microK instruction provided on screen before the update process starts it will take about 5 minutes The update software will only update either the software or firmware at each attempt so if you are updating both you will need to press Update Software twice The software automatically checks any USB flash drive connected to the front panel at start up If a more recent software version is found you will be offered the opportunity to upgrade Some flash drives enumerate too slowly and so are not detected during the start up routine in this case you should use the manual update procedure described above 3 7 6 Select Language Press the Select Language button to change the User Interface language Select Language WH A EN English O Chinese Changing the language will require the software to be restarted OK Cancel Press the flag or the adjacent radio button to select the language then press OK to implement the change Page 34 of 85 GRIES Issue 1 01 _ISOT CH 3 7 7 Change Password Press the Change Password button to change the security password see section 3 1 for details of password
54. easure a Default PRT at mA against the internal 400 reference on the 500Q range on channel other channels disabled Set the units to Ohms and use sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Single tab and clear the statistics After the microK has collected at least 100 readings shown as Mean of last in the Single tab check that the Mean agrees with the calibrated value of the resistance standard to within 2 5ppm half of the specification limit of the calibrated value and that the standard deviation S D is less than 0 00008 7 1 2 3 100 Q Internal Reference Resistor Repeat the procedure for checking the 400Q internal reference see section 7 1 2 2 but configure the microK to measure a Default PRT at ImA against the internal 100Q reference on the 125 range on channel I 7 1 2 425 O Internal Reference Resistor Repeat the procedure for checking the 400Q internal reference see section 7 1 2 2 but configure the microK to measure a Default PRT at ImA against the internal 25Q reference on the 125 range on channel l 7 1 2 5 10 O Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 10 to channel Ideally this should be a Wilkins resistor with a recent traceable calibration certificate maintained at a constant temperature in an oil bath Repeat the procedure for checking the 400Q internal reference see section 7 1 2 2 but
55. ect operation of the measurement system It only needs to be checked on one channel 7 1 2 1 Zero Ohms Check Start by applying a four terminal short circuit to channel This involves shorting out the voltage sense terminals marked V and the current terminals market I and then making a single connection between these two set of terminals The objective is to ensure that none of the sense current passes along the wire between the voltage sense terminals This can easily be achieved using a single piece of un insulated wire V l 4 Terminal Short Circuit Configure the microK to measure a Default PRT at mA against the internal 100Q reference on the 125Q range on channel other channels disabled Set the units to Ohms and use sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Single tab and clear the statistic After the microK has collected at least 100 readings shown as Mean of last in the Single tab check that the Mean is less that 0 00001 10UQ i e 0 08ppm of the 125Q range and that the standard deviation S D is less than 0 00005 Page 53 of 85 GRIES Issue 1 01 _ISOT CH 7 1 2 2400 O Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 00Q to channel Ideally this should be a Wilkins resistor with a recent traceable calibration certificate maintained at a constant temperature in an oil bath Configure the microK to m
56. ename An automatically incrementing default name will appear in the entry box press OK to accept this or use the backspace and alpha numeric keys to enter your preferred filename If you try to use a filename that has already been used you will have to enter the password to proceed see section 3 1 for details on password protection The Shift key toggles the alpha keys between upper and lower case The indicator by the Start Save button in the Single tab shows whether readings are being recorded to a file The measurements are written to the file in comma delimited ASCII text form allowing easy importation into Microsoft Excel or other applications 3 5 The Multi Tab Select this tab to see all three channels in numeric form only The numeric display shows the last reading together with the mean and standard deviation for the most recent readings the number of readings in the statistics is set in the Settings tab for each of the channels that are enabled Page 24 of 85 GRIES Issue 1 01 _ISOT CH _ Single Multi Settings Instrument sse 09 0 0000008 vors 0 000000753 Mean of last 100 0 000000016 SD Clear Channel 2 99 9983 Ohms 99 998279 Mean of last 100 0 000022 SD pu Channel 3 Rt Rs Clear buttons Press the Clear button to clear reset the statistics for each channel The displayed values are updated as new
57. ge 0 5V current resistance range 2 5V current The resistance range specified should be the higher of the maximum PRT resistance and reference resistor since the measurement system has to measure the signal across both to determine the resistance of the device under test Example to set the microK to measure a PRT that has a maximum resistance of 30Q using a 100Q reference resistor with a mA sense current use SENS FRES RANG 130 1 This will set the microK to the middle range 10 4 12 Command SENSe FRESistance RANGe Format SENSe FRESistance RANGe UPPer Reports the range for the next resistance measurement at the present sense current set using the CURRent command The current used to calculate the range may be different from that specified when the range was set using the SENSe FRESistance RANGe command The reported range is the actual range for the measurement system at the present sense current Example a microK that has had its resistance range set using the command shown in section 10 4 1 but has its sense current set to OmA would respond to the command SENS FRES RANG with 50 000000 Page 74 of 85 ORELE Issue 1 01 _ISOT CH 10 4 13 Command SENSe RATio REFerence Format SENSe RATio REFerence reference channel Selects the reference channel for the next resistance ratio measurement made The channel is not actually selected until a measurement is started using with either the INIT
58. he reference resistor used in the resistance measurement either one of the internal reference resistors or the channel to which an external resistance standard is connected Alternatively press the ellipses button to open the Reference Channel window and select the channel directly The External button in this window allows you to select one of the microK s three external channels or any expansion channel provided by a microsKanner Reference Resistor box PRTs and thermistors only If an internal reference resistor was selected in the Reference Channel box this box will show the calibrated value of that resistor If one of the input channels was selected in the Reference Channel box this box will contain a list of the reference resistors in the microK s database entered using the Edit Resistors button in the Instrument tab see section 3 7 2 and Uncalibrated Select the required resistor using the up down buttons Select Uncalibrated if you only want to make a resistance ratio measurement between two channels The ellipses button opens a list of all available reference resistors and is useful if you have a large number of entries in the database Reference Junction box thermocouples only This contains 0 C 0 01 C and a list of any input channels that have been configured to measure temperature Choose 0 C or 0 01 C if you are using an external reference junction in an ice point bath or water triple point respectively Choo
59. he applied voltage to within 0 000000250V 0 254 V and that the standard deviation S D is less than 0 000000050V 0 05uV Repeat the procedure with the voltage source set to 50mV 7 2 Adjusting Calibration This section describes the procedures for adjusting the internal reference standards and the input offset voltages These can be performed by the user or a third party calibration provider subject to the availability of the standards specified below Isothermal Technology additionally checks the temperature coefficient of the zener reference and the linearity of the microK against an RBC resistance bridge calibration with an uncertainty of 0 0 ppm We therefore recommend that you return your microK to Isothermal Technology or one of its appointed service centres annually for a comprehensive instrument calibration There are no potentiometers inside the microK to adjust calibration is implemented in software so can be performed without removing the cover from your microK Calibration is adjusted via the RS232 interface on the rear of the microK Connect the microK to a PC using a 9 pin null modem RS232 cable and establish an RS232 connection with it using Hyperterminal at 9 600 Baud for further details of how to connect a PC to your microK see section 8 1 Confirm that the RS232 link is working by typing in IDN terminate this and all commands shown in this section by pressing the carriage return or enter key The microK will resp
60. he microK should be powered up and left to stabilise in the calibration environment for at least 4 hours before checking or adjusting its calibration 7 1 1 Checking the Master Current Source The microK current source has 3 ranges 0 0 I mA 0 I mA and 0 10mA Check these by connecting a calibrated ammeter or DMM across the current terminals of channel and connecting both the sense inputs to the red current terminal e v9 Checking the master current source involves connecting a PC to your microK using a null modem RS232 cable and sending commands to it from Hyperterminal part of the standard Windows operating system installation or another terminal emulator For further details of how to connect a PC to your microK see section 8 Once you have established communication with your microK type in the following commands and check that the measured current is within the given limits Page 52 of 85 GRIES Issue 1 01 _ISOT CH command current limits TEST CURR 0 0 0996 to 0 1004 mA TEST CURR 0 996 to 1 004 mA TEST CURR 10 9 96 to 10 04 mA TEST CURR O 0 09966 to 0 1004 mA TEST CURR I 0 9966 to 1 004 mA TEST CURR 10 9 96 to 10 04 mA 7 1 2 Resistance Measurements The current reversal used by the microK to eliminate the effect of thermal EMFs means that it has an inherently stable zero for resistance measurement The zero ohms test does not form part of the calibrations process but is used to confirm corr
61. his icon to open an RS232 connection with your microK Type IDN into Hyperterminal terminate the command by pressing the carriage return or Enter keys the microK should then respond with a string in the form Isothermal Technology microK 250 1 P321 firmware version 1 24 This confirms that you have successfully established an RS232 connection with your microK Page 63 of 85 GRIES Issue 1 01 _ISOT CH 9 GPIB The microK is equipped with an IEEE 488 GPIB General Purpose Interface Bus port This can be used to control the microK and perform calibration and diagnostic functions The command set uses the SCPI Standard Commands for Programmable Instruments protocol see section 10 for details The GPIB connector is located on the rear of your microK see section 1 4 The connector is the standard IEEE 488 connector 24 way Pin Name Function Pin Name Function DIOI Data Input Output bit 13 DIO5 Data Input Output bit 2 DIO2 Data Input Output bit 14 DIO6 Data Input Output bit 3 DIO3 Data Input Output bit 15 DIO7 Data Input Output bit 4 DIO4 Data Input Output bit 16 DIO8 Data Input Output bit 5 SEO End or Identify I7 REN_ Remote Enable 6 DAV Data Valid 18 GND Ground paired with DAV 7 NRFD Not Ready for Data 19 GND Ground paired with NRFD 8 NDAC Not Data Accepted 20 GND Ground paired with NDAC 9 IFC Interface Clear 21 GND Ground paired with IFC 10 SRQ Service Request 22 GND Ground paired with SRQ II AT
62. iate or READ commands Example to select channel 2 as the reference channel for the next resistance ratio measurement use SENS RAT REF 2 10 4 14 Command SENSe RATio REFerence Format SENSe RATio REFerence Reports the channel selected as the reference channel for the next resistance ratio measurement Example a microK set to use channel 2 as the reference in the next resistance ratio measurement will respond to the command SENS RAT REF with 2 10 4 15 Command SENSe RATio RANGe Format SENSe RATio RANGe UPPer resistance range current Sets the range for the next resistance ratio measurement The range is determined by the voltage range of the measurement system 0 125 0 5 or 2 5V and depends on the sense current used The current parameter is the current you intend to use in the measurement this may not be the same as the present value of sense current that is set with the CURRent command The 3 resistance ranges available with the microK are resistance range 0 125V current resistance range 0 5V current resistance range 2 5V current The resistance range specified should be the higher of the maximum PRT resistance and reference resistor since the measurement system has to measure the signal across both to determine their ratio Example to set the microK to measure the resistance ratio of a PRT that has a maximum resistance of 130Q with a 1000 reference resistor with a mA sense current
63. ing marked on the rear panel If a replacement fuse fails immediately contact your local service agent DO NOT replace with a higher value Always use the power cord supplied Your sales outlet can provide a lead suitable for your country This equipment is for use in moderate climates only NEVER use the equipment in damp or wet conditions Avoid excessive heat humidity dust amp vibration Do not place liquid filled containers on the equipment Do not use where the equipment or any associated accessories may be subjected to dripping or splashing liquids Ensure that the power switch is easily accessible to allow the unit to be switched off The equipment weighs 3kg use the handles provided Always disconnect the equipment from the electrical supply and any ancillary units before moving Ensure that tabletop equipment is placed on a solid level surface which is able to support its weight and that of any attached accessories Ensure all cables and wires are routed safely to avoid tripping also to avoid sharp bends and pinches Clean only with a damp cloth Do not wet or allow moisture to penetrate the unit Do not use solvents See section 5 1 for details of cleaning procedure The product should be subjected to regular in service inspections as required by local regulations a yearly interval is suggested Verify that the supply cordset is undamaged and that the enclosure is bonded to protective earth
64. ing the Reference Resistor box in the Settings tab see section 3 6 Page 38 of 85 GRIES Issue 1 01 _ISOT CH The database allows you to enter information about the reference resistor Resistor Name the name you use to refer to the resistor Manufacturer s name Serial Number Calibration Due date Value calibrated value in ohms EE S EE Gs EE Information in the database is password protected to help you comply with the reguirements of accreditation bodies 3 10 Saving Instrument Configurations You can save the current configuration settings for the microK using the Backup Configuration button in the Instrument tab see section 3 7 12 This is useful if you use the microK in a number of different ways for example at different times you may use it to perform fixed point calibrations on single SPRTs and comparison calibrations of a thermocouple against two SPRTs You can then reload the required configuration see section 3 7 13 rather than having to enter all the setting for that particular measurement configuration individually 3 11 Password Protection of Key Settings All settings and parameters that affect measurements are password protected This helps you to establish working procedures that meet the requirements of accreditation bodies and should alleviate some of the concerns that accreditation bodies have about the integrity of measurements You need to enter the password to perform the following tasks
65. kup Configuration Change Password Select Language Load Configuration 3 7 1 Edit Thermometers Press Edit Thermometers to create edit or delete a thermometer in the database You will be prompted to enter the password in order to proceed Page 29 of 85 GRIES Issue 1 01 fr ISPRTL n Thermometer Thermometer Type Thermometer Name SPRT1 tT IERT IL Manufacturer s Name in Temperature C Isothermal Technology m 0 00 Se Serial Number ax Temperature C 66032 123 8 660 00 Ss Calibration Due Conversion 15 12 2010 I fr ITS90 IL New Delete Coefficients OK Thermometer box Use the up down buttons to select the thermometer you wish to edit or delete Alternatively press the New key to create a new thermometer entry The default thermometer types are included in the list but cannot be edited or deleted Thermometer Name box This box contains the name of the selected thermometer If you are creating a new thermometer entry the ellipses button by the box becomes active Press this button to open an Alpha Numeric Keyboard window and enter a name The Shift key toggles the alpha keys between upper and lower case Manufacturer s Name box This box contains the manufacturer of the selected thermometer If you are creating a new thermometer entry the ellipses button by the box becomes active Press this but
66. ld be to use a multi bit ADC and DAC in the feedback loop This would not normally be feasible since the DAC would carry the full accuracy burden of the measurement system However by using a PWM Pulse Width Modulation DAC in which the output is a signal of fixed frequency and amplitude but variable pulse width we turn the problem of producing accurate voltage or current levels into one of accurate timing Whereas achieving sub ppm voltage accuracy with a DAC would not be feasible in this sort of product it is possible to achieve the corresponding timing accuracies 4 integrators Low buffer Accuracy e fe gt p ie Gi anc LOGIC La Precise EEN output 5 bit DAC Der value Decimator Multi Bit X A ADC The timing demands of the PWM DAC are however far from trivial The digital filter has to work at the X A ADCs clock rate In the microK this digital part of the X A ADC is implemented in a fast FPGA which provides both the digital filter that decimates the DAC output to extract the converted value and controls the feedback DAC The full scale pulse width on the PWM DAC is only bus so the 0 25ppm linearity achieved with the X A ADC corresponds to a timing accuracy of 25ps or about the time it takes for the electrical signals in the control system to travel less that 0 4mm It might appear that the reduction in quantisation noise from using multi bit feedback in a X A ADC would be directly proportional to the ADC DA
67. ls to perform the required measurement Instrument allows you to enter information on the thermometers and reference resistors used with the instrument into its database It also allows you to save load measurement data and instrument configurations in the database and to change instrument settings such as the GPIB address time date and security passwords The Main Window opens with the Single tab selected 3 4 The Single Tab Select this tab to see a single channel in both numeric and graphical form Single Multi Settings Instrument Channel ol ol Clear Graph 4 2538 ec 4 253776 Mean of last 100 e smse s kee S 4 2490000e0 4 2500000e0 4 2510000e0 4 2520000e0 4 2530000e0 4 2540000e0 fi en tee P HIP ASI e writin ANN AS NE 4 2550000e0 4 2560000e0 4 2570000e0 4 2580000e0 700 750 800 850 900 950 Time j s Channel box Use the up down buttons by the Channel box to select the channel you wish to view Alternatively press the ellipses button to open a numeric entry window and select the channel directly The ellipses button is particularly useful when the microK is used with microsKanner multiplexers which can provide up to 90 expansion channels You can only view channels that are enabled so if a channel is disabled in the Settings tab it will not appear in the sequence and will not be measured This means that the up down butto
68. lue assigned to the 10Q internal reference is CAL REF202 RIO Where R10 is the value calculated for the 10 internal reference 7 2 6 Calibrating the Q Internal Reference Resistor Connect a stable external resistance standard with a nominal value of Q to channel Ideally this should be a Wilkins resistor with a recent traceable calibration certificate Repeat the procedure for calibrating the 400Q internal reference see section 7 2 2 but configure the microK to measure a Default PRT at IOmA against the internal reference on the 13 range on channel The command to adjust the value assigned to the Q internal reference is CAL REF201 RI Where RI is the value calculated for the Q internal reference 7 2 7 Calibrating Voltage Zeros Short out the 4 measurement terminals on all 3 channels using a piece of un insulated copper wire use pure copper wire to avoid generating unwanted thermal EMFs for each channel V Type in the following commands to remove the zero offset correction for all three channels CAL OFFSI 0 CAL OFFS2 0 CAL OFFS3 0 Configure the microK to measure a Default Thermocouple on the 0 125V range with units of Volts on all 3 channels Use sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Multi tab and clear the statistics for all 3 channels After the microK has collected at least 100 readings Page 59 of 85 GRIES Issue 1 01 _ISOT CH shown as
69. micro User Maintenance Manual Handbook Issue 1 01 Applies to Models microK 250 and microK 500 Software version 1 4 29 Firmware version 3 21 NPL National Physical Laboratory Technology Applied Isothermal Technology Limited Pine Grove Southport PR9 9AG England Tel 44 0 1704 543830 Fax 44 0 1704 544799 Internet www isotech co uk E mail info isotech co uk The company is always willing to give technical advice and assistance where appropriate Equally because of the programme of continual development and improvement we reserve the right to amend or alter characteristics and design without prior notice This publication is for information only _ISOT CH CONTENTS INTRODUCTION es sesse ees esse sek Ses ENG Geo do AA ER Ge sg ee ee Gog sed de 1 1 Unpacking 7 1 2 Safety RE ER RE EE E RE NO OE Sect os EO EE EE ON 7 1 3 Powering Up Your micro 8 1 4 A Quick Tour of Your microK issie sessies oe ee sae tree pa ske no aa oae ERG eoe ee ee EE ore ode oe SEES ed AE Eae ed GE EE eed eo ee ee ad EE ee DE EE 9 2 1 Measuring Temperature with a Calibrated SPRT scccccccsssssssssssssssssssssssscecesscsscssssssessesssoscssessesseessosees 12 2 2 Measuring Temperature with a Thermocouple sscccccscsssssssssssscsscssssssssscesesscsscsscsscssesscsscsseesessesssosees 16
70. n channel 2 using the 100 ohm range and a sense current of I mA would be MEAS FRESI REF2 100 1 10 2 3Units Numeric parameters may optionally include units The standard multiplying prefixes may also be used to indicate decimal multiples or fractions For example the following are all equivalent CURRENT 0 001A CURRENT Ima CURRENT 1000UA CURRENT The following prefixes are available prefix name factor Norn nano 10 Uoru micro 10 Morm milli 10 Kork kilo 10 MA orma mega 10 Page 68 of 85 CES Issue 1 01 _ISOT CH 10 3 Making Measurements using SCPI Commands The microK s measurement system is controlled by a microprocessor connected to the rear panel RS232 interface and a GPIB port The measurement system can be controlled by SCPI commands from either of these The firmware makes no distinction between commands received on the RS232 interface and those from the GPIB and will process these in the order in which they are detected If a response is expected it will always be sent on the interface RS232 or GPIB on which the corresponding command was sent There is no direct interference between measurements made using the front panel operator interface and measurements requested using SCPI commands However measurements take some time to complete so there may be a delay in responses to SCPI commands if measurements are being made via the front panel operator interface To avoid unnecessary delays to responses to
71. nals of the microK becoming electrically live and therefore a hazard to the operator Suitable precautions should be taken such as using an isolating transformer in the supply to such a furnace If you require further advice on safety issues please contact Isothermal Technology or one of our appointed distributors we have extensive experience of thermometry and can provide advice and equipment to help you Retain these instructions Use only as specified in these operating instructions or the intrinsic protection may be impaired Please observe the following safety precautions Do not use your microk if it is damaged Only connect to an earthed supply socket THIS UNIT IS CLASS CONSTRUCTION AND MUST BE EARTHED Connect only to a power supply with a voltage corresponding to that on the rating plate This equipment is for indoor use and will meet its performance figures within an ambient Page 7 of 85 GRIES Issue 1 01 _ISOT CH temperature range of 5 C to 40 C with maximum relative humidity of 80 for temperatures up to 31 C decreasing linearly to 5096 RH at 40 C Equipment is for operation at installation category Il transient voltages and pollution degree ll in accordance with IEC 664 at altitudes up to 2000 metres Before replacing a fuse DISCONNECT THE EQUIPMENT FROM THE ELECTRICAL SUPPLY The fuse is contained in the IEC socket on the rear panel It must only be replaced with a fuse of the type and rat
72. ns have no effect if only one channel is enabled Page 22 of 85 GRIES Issue 1 01 _ISOT CH The numeric display shows the last reading together with the mean and standard deviation of the most recent of readings the number of readings in the statistics is set in the Settings tab Clear Graph Press the Clear Graph button to clear the graph and re start the autoscaling feature This can be used to eliminate the effect of a large transient result perhaps caused when changing connections to the thermometer on the autoscaling function Clear button Press the Clear button to clear reset the statistics Set Scales button Use the Set Scales button to open a new window and set the x and y axes for the graphical output Y Axis X Axis Channel Scale Seconds t li tt o g inimum Time Units 0 Seconds 10 O Autoscale aximum O Minutes OK Cancel In this window use the up down buttons by the Channel box to select the channel whose scales you wish to change the window opens with the currently displayed channel selected Use the radio buttons to select either Seconds or Minutes as the units Use the up down buttons by the Scale Seconds box to change the x axis time scale the same x axis scale is used for all channels Or press the ellipses button to open a Numeric Keypad window and enter the required scale directly Any value between second and 1000 mi
73. ns to select the required thermometer Initially this box will contain only default PRT Thermocouple or Thermistor You can use these entries for uncalibrated thermometer sensors If you add thermometers to the microK s Thermometer Database see section 3 7 1 these will also appear in the list within this box The ellipses button opens a list of all available thermometers and is useful if you have a large number of entries in the database Conversion box If the selected thermometer is one of the default types you can use the up down buttons to select a standard polynomial function for converting the thermometer s base measurement to temperature If the selected thermometer is one that your have created in the Thermometer Database this box will be fixed and will be the conversion type defined for that thermometer Page 26 of 85 GRIES Issue 1 01 _ISOT CH Range box Use the up down buttons to select the required range The microK has three ranges for each thermometer type Use the 0 125V range for all thermocouples as this provides the most suitable input voltage range The resistance ranges offered depend on the sense current use the ellipses button by the Current box in this tab to change the current Choose a resistance range that is greater than or equal to both the highest thermometer resistance and reference resistor value you intend to use Reference Channel box PRTs and thermistors only Use the up down buttons to select t
74. nsion a cable 4 2 Connecting PRTs 4 wire The microK s resistance measurement system is optimised for high accuracy 4 wire resistance measurement The PRT should be connected to the chosen input channel in accordance with the schematic shown on the microK s front panel as follows SPRT The top terminal should be connected to the screen of the SPRT s lead to minimise electrical noise picked up by the wires Page 40 of 85 GRIES Issue 1 01 _ISOT CH 4 3 Connecting PRTs 3 wire The microK can be connected to 3 wire PRTs although it will not automatically compensate for cable resistance The two red terminals should be connected together and then connected to the single end of the 3 wire PRT as follows PRT The connection to the single end of the 3 wire PRT should be short have a low resistance in order to minimise the effect of lead resistance on the measurement The top terminal should be connected to the screen of the PRT s lead to minimise electrical noise picked up by the wires 4 4 Connecting PRTs 2 wire The microK can be connected to 2 wire PRTs The two red and two black measurement terminals should be connected together and then connected to the PRT as follows PRT The connections to the PRT should be short low resistance in order to minimise the effect of lead resistance on the measurement Alternatively the connections can use remote sensing using the 4 wire measurement c
75. nt gt Example to set the sense current on channel to 5mA use TEST CURR 5 10 4 26 Command CALibrate CURRent Format CALibrate CURRent actual current gt This command is used after using the TEST CURR command and measuring the current from channel see section 7 2 1 It uses the actual current entered to adjust the master current source the correct current Example the current from channel after using the command TEST CURR was measured as 1 00123 To adjust the master current source correctly use CAL CURR 1 00123 10 4 27 Command CALibrate REFerence Format CALibrate REFerence reference gt actual resistance gt Used to calibrate the internal lt reference gt standard by assigning a new actual resistance gt to it The channel numbers numeric suffices used for the internal resistor are given in section 10 2 1 The calibrated value is stored as a floating point number and will therefore be subject to some rounding less than 0 2ppm of value Example if the value of the internal 00Q reference has been measured as 100 00123 the new value can be assigned to it using CAL REF204 100 00123 10 4 28 Command CALibrate REFerence Format CALibrate REFerence reference Used to report the calibrated value of the internal lt reference gt resistor used by the microK to calculate resistance Example a microK with an internal 25 reference having a calibrated value of 25 01234 will resp
76. nutes inclusive may be used Use the ellipses by the Minimum and Maximum boxes to open a Numeric Keypad window and set the y axis scale Alternatively press the Autoscale button to scale the y axis so that it will show all the readings The indicator by the Autoscale button shows whether autoscaling is active Page 23 of 85 GRIES Issue 1 01 _ISOT CH The numeric and graphical outputs are updated as new readings are made The time between readings depends on the settings for that channel and any other channels that are also enabled This can vary between 2 seconds and 5 minutes The measurement sample time for a PRT or thermistor is 2s and for a thermocouple it is lt Is The reading rate for three PRTs with one sample per reading will therefore be lt 6s Start Save button Press the Start Save button to record all the measurements being made You will then be offered the choice buttons of storing the data to the Internal DiskOnChip solid state drive memory or an External USB flash drive Data stored to the internal memory can subsequently be transferred to an external USB flash drive using the Backup Data button in the Instrument tab see section 3 7 10 The internal memory used has a capacity of at least 32Mbytes this will accommodate approximately 300 000 PRT readings or about 30 days of continuous logging at the fastest rate Select the destination for the data to open an Alpha Numeric Keyboard window and enter a fil
77. ommands and checking that the current is within the given limits command current limits TEST CURR O I 0 09975 to 0 10025 mA TEST CURR 10 9 975 to 10 025 mA TEST CURR 0 1 0 09975 to 0 10025 mA TEST CURR 0 9975 to 1 0025 mA TEST CURR 10 9 975 to 10 025 mA 7 2 2 Calibrating the 400 Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 00Q to channel Ideally this should be a Wilkins resistor with a recent traceable calibration certificate maintained at a constant temperature in an oil bath Configure the microK to measure a Default PRT at mA against the internal 400 reference on Page 57 of 85 GRIES Issue 1 01 _ISOT CH the 500Q range with channel other channels disabled Set the units to ratio Rt Rs with sample per reading and 100 readings in the rolling statistics see section 3 6 Select the Single tab and clear the statistics After the microK has collected at least 100 readings shown as Mean of last in the Single tab record the Mean value and check that the standard deviation S D is less that 0 000000100 Calculate the value of the internal resistor from exernalreference R400 ratio Adjust the value assigned to the internal 400Q reference resistors by typing in the command CAL REF205 R400 The value entered can be read back using CAL REF205 Check the new value assigned to the internal 400Q reference resistor see section 7 1 2 2
78. on uses upper case to indicate required letters and lower case to indicate optional letters NB all commands are case insensitive For example valid forms of the above command include Sense Fresistance Reference SENS FRES REF Sense fresistance REF To shorten the commands default optional keywords are enclosed in square brackets and may be omitted For example in the case of the command MEASure SCALar VOLTage DC Valid forms of this command include MEAS VOLT MEASURE SCALAR VOLTAGE DC 10 2 1 SCPI Numeric Suffices In order to support multiple input channels commands can include numeric suffices These are represented by a hash in the command notation for example MEASure VOLTage lt channel gt In addition to the 3 input channels on the front panel which are assigned the suffices 2 and 3 the internal reference resistors are specified using numeric suffices as follows Page 67 of 85 GRIES Issue 1 01 _ISOT CH channel Internal reference resistor 201 IQ 202 10 Q 203 25 Q 204 100 Q 205 400 Q In order to measure the voltage on channel 3 the command used would be MEAS VOLT3 10 2 2Parameters If a command requires parameter s these follow the command and are separated from it by a space If more than one parameter is required each parameter is separated by a comma For example the command to measure a four terminal resistance on channel against a reference resistor o
79. ond to CAL REF203 with 25 01234 Page 79 of 85 ISUT CH Issue 1 01 _ISOT CH 10 4 29 Command CALibrate OFFSet Format CALibrate OFFSet lt channel gt lt offset gt Adjusts the voltage offset for lt channel gt used when making voltage measurements The offset range is JUN attempts to apply an offset greater than this will be ignored The offset is stored as a floating point number and will therefore be subject to some rounding less than 0 2ppm of value Example to subtract an offset of 0 23uV from voltages measured on channel 3 use CAL OFFS3 0 123 10 4 30 Command CALibrate OFFSet Format CALibrate OFFSet channel gt Reports the offset subtracted from voltage measurements on channel gt Example a microK that has been calibrated to have a 0 123uV offset subtracted from voltage measurement on channel 2 will respond to CAL OFFS2 with 1 23E 07 10 4 31 Command CALibrate GAIN Format CALibrate GAIN gain polarity adjustment 7 Adjusts the value of gain for polarity by the factor adjustment The parameter lt gain gt must be one of three strings defining the nominal gain of the microK pre amplifier L X2 XIO X40 The parameter lt polarity gt must be either POSitive or NEGative The gain adjustment is stored as a floating point number and will therefore be subject to some rounding less than 0 1 2ppm of value Example for a microK that has been found to have
80. ond with a string in the form Isothermal Technology microK 250 1 P321 firmware version 1 24 The calibration of your microK is password protected Unlocked the calibration to allow calibration adjustment using the command CAL UNL password where password is the calibration system password NOT necessarily the same as the password used in the touch screen operator interface The password is Page 56 of 85 GRIES Issue 1 01 _ISOT CH initially set to 1234 but should be changed for security reasons see section 10 4 33 You can now use the SCPI commands see section 10 4 detailed below to adjust the microK s calibration 7 2 Calibrate Master Current Source The microK s current source has 3 ranges 0 0 mA 0 ImA and 0 10m4A The tolerance between the ranges is sufficiently small that it is only necessary to calibrate the mA range in order to achieve the full performance specification Connect a calibrated ammeter or DMM across the current terminals of channel and connect both the sense inputs to the red current terminal JO I Send the command TEST CURR to your microK from Hyperterminal this forces the microK to source ImA on channel Measure the current and then type in the command CAL CURR current where current is the measured value Now type in TEST CURR 1 again to update the current source The ammeter should now read mA 0 0003mA Check the other current ranges by typing in the following c
81. pond to the command SENS VOLT RANG with 0 125 10 4 9Command SENSe FRESistance REFerence Format SENSe FRESistance REFerence lt reference channel gt Selects the reference channel for the next resistance measurement made The channel is not actually selected until a measurement is started using with either the INITiate or READ commands Example to select channel 204 internal 100 ohm resistor as the reference channel for the next resistance measurement use SENS FRES REF 204 Page 73 of 85 OSE LES Issue 1 01 _ISOT CH 10 4 10 Command SENSe FRESistance REFerence Format SENSe FRESistance REFerence Reports the channel selected as the reference channel for the next resistance measurement Example a microK set to use channel 204 as the reference in the next resistance measurement will respond to the command SENS FRES REF with 204 10 4 11 Command SENSe FRESistance RANGe Format SENSe FRESistance RANGe UPPer resistance range current Sets the range for the next resistance measurement The range is determined by the voltage range of the measurement system 0 125 0 5 or 2 5V and depends on the sense current used The current parameter is the current you intend to use in the measurement this may not be the same as the present value of sense current that is set with the CURRent command The 3 resistance ranges available with the microK are resistance range 0 125V current resistance ran
82. protected settings A window will then open to allow you to change the password Old Password m New Password AT Confirm New Password OK Cancel You will need to enter the old password and the new one twice to ensure that it has been correctly entered Press the ellipses buttons by each of the password boxes to open an Alpha Numeric Keyboard window and enter the relevant password Your microK is shipped with the password set to 1234 This should be changed for security reasons before using your instrument in earnest 3 7 8 Port Settings Press Port Settings to view and change the microK s GPIB address RS232 Baud Rate 9600 GPIB Address ol 10 al OK Cancel Press the ellipses button to open a numeric entry window and change the GPIB address valid range to 30 inclusive The Baud Rate box reports the baud rate for the RS232 port but this cannot be changed Page 35 of 85 GRIES Issue 1 01 _ISOT CH 3 7 9 Set Date and Time Press Set Date and Time to change the date and or time This opens a window to allow you to enter the current date and time and to select the date format dd mm yyyy or mm dd yyyy Year 2011 Date Format dd mm yyyy lonth 11 S O mm dd yyyy Day 15 E Hour 15 m inute 47 n Second 56 ge OK Cancel Press the ellipses buttons by each box to open
83. ration adjustment The microK always powers up in the locked state Calibration can be re locked by re powering the microK or using CAL LOCK see section 10 4 35 Example to unlock enable the calibration adjustment on a microK with the default password 1234 use CAL UNL 1234 10 4 35 Command CALibrate LOCK Format CALibrate LOCK Locks the microK to prevent calibration adjustment Example to lock the calibration of a microK after adjustment use CAL LOCK Page 81 of 85 GRIES Issue 1 01 _ISOT CH I Specification Ranges Accuracy PRTs Accuracy Thermocouples Resolution Stability Measurement Time Temperature Conversions ISUT CH Resistance Thermometers OO to 500k Q Thermocouples 125mV uK250 0 06ppm maximum ratios 0 95 to 1 05 for SPRT with Rz 2 50 equivalent to 0 06mK 0 25ppm maximum over whole range for SPRT with R 2 2 50 equivalent to 0 25mK I ppm maximum over whole range for SPRT with R 0 25Q uK500 0 125ppm maximum ratios 0 95 to 1 05 for SPRT with R z 2 5O equivalent to 0 125mK 0 5ppm maximum over whole range for SPRT with R 2 2 50 equivalent to 0 5mK 2ppm maximum over whole range for SPRT with R0250 Voltage uncertainty 50nV between 0 and 20mV equivalent to 0 01 C for Gold Platinum thermocouple at 1000 C Resistance 0 01 ppm of range 0 01 mK for an SPRT Voltage OnV 125mV range Resistance excluding resistance s
84. red can be read back using CAL GAIN X40 POS Repeat the procedure with the voltage source set to 5OmV Apply the new negative polarity gain by typing in the command CAL GAIN X40 NEG gain The value entered can be read back using CAL GAIN X40 NEG Page 61 of 85 GRIES Issue 1 01 _ISOT CH 8 RS232 Interface The microK is equipped with an RS232 interface This can be used to control the microK and perform calibration and diagnostic functions The command set uses the SCPI Standard Commands for Programmable Instruments protocol see section 10 for details 8 1 Establishing an RS232 Connection The RS232 connector is located on the rear of your microK see section 1 4 The connector is a 9 way male D type configured as a standard DTE device Pin Name Function CD carrier detect not connected 2 RD receive data 3 TD transmit data 4 DTR data terminal ready fixed high 5 SG signal ground 6 DSR data set ready not connected 7 RTS request to send 8 CTS clear to send 9 not used not connected Shell FG frame ground screen Connect your microK to a PC using a standard null modem cable i OO JO Om Po OO OO JO Oo KON Shell n 2 2 Null Modem Cable The format for the RS232 interface is as follows Baud Rate 9 600 Start Bits Stop Bits Parity Bit none The microK has a 256 byte circular receive buffer If the buffer becomes full it de asserts RTS connected to CTS on your
85. resistance range gt current voltage range gt resistance range gt current resistance range gt current current gt current gt actual current gt actual resistance gt offset gain polarity gt adjustment gain polarity gt old password lt password lt password password A detailed description of each command follows 10 4 1 Command IDN Format IDN Reports information on the microK in 4 comma separated fields manufacturer model serial number firmware version EE S Gs EE ISUT CH Page 71 of 85 Issue 1 01 _ISOT CH Example for a microK 250 with serial number 261067 1 using firmware version 1 24 the microK responds to IDN with Isothermal Technology microK 250 261067 firmware version 1 24 10 4 2Command RST Format RST Performs a reset equivalent to a power on reset of the measurement system firmware 10 4 3Command SENSe FUNCtion Format SENSe FUNCtion function Selects the measurement function The parameter function must be one of the following valid SCH parameters VOLTage DC FRESistance RATio Example to set the microK to measure ratio use SENS FUNC RAT 10 4 4Command SENSe FUNCtion Format SENSe FUNCtion Reports the current measurement function Example a microK set to measure voltage will respond to SENS FUNC with VOLTAGE 10 4 5Command SENSe CHANnel Format SE
86. se one of the measurement channels if you want to measure the temperature of the reference junction with a thermometer sensor on that channel The software will not allow you to use a thermocouple channel as the reference junction sensor to avoid circular dependencies You must specify a thermometer sensor for the reference junction channel that includes temperature conversion otherwise it will not appear in the Reference Junction box Units box Use the up down buttons to select the required units The base units resistance ratio Rt Rs for PRTs or thermistors and Volts for thermocouples are always available Ohms will also be available for PRTs and thermistors if the value of the reference resistor is available Reference Resistor not set to Uncalibrated If the thermometer sensor chosen has a temperature conversion specified then temperature units C F and K are also available Page 27 of 85 OSE LES Issue 1 01 e Current box PRTs and thermistors only Press the ellipses button to change the sense current Use the buttons in the window that then opens to select the required sense current 1 0000 mA O 1mA 2mA Custom 0 5mA 5mA 2 imA 10mA x v2 OK Cancel The standard PRT sense currents are available directly through the buttons provided Press the Custom button to specify a different value range 0 to 10mA this will then open a Numeric Keypad window
87. ses button to open a Numeric Keypad window and enter the required number directly The number of samples may be between and 100 inclusive Page 28 of 85 GRIES Issue 1 01 _ISOT CH Increasing the number of samples will slow down the rate at which readings are made but will also reduce the uncertainty associated with these readings as shown by the standard deviations reported in the Single and Multi tabs This uncertainty reduction is proportional to the square root of the number of samples for example selecting 9 samples per reading will reduce the uncertainty associated with each reading by a factor of 3 Readings in Rolling Statistics box Use the up down buttons to select the number of samples in the rolling statistics Alternatively press the ellipses button to open a Numeric Keypad window and enter the value directly Values between and 1000 inclusive may be used 3 7 The Instrument Tab Select this tab to enter information into the microK s database for thermometers and reference resistors adjust instrument settings GPIB address time date and passwords backup load instrument configurations or update the software Single Multi Settings Instrument System Calibration Edit thermometers Port Settings e c Edit Resistors Set Date and Time Calibration Backup Data Restart Software Clear Data Files Update Software Bac
88. sies ere RR rh EE ER ee ee Ede ER CEST ERE RD EET Ee GEGEE 78 10 4 25 Command TEST CURReNt ees ee ee ee ee ee ee ee ee ee ee ee ee Re ee ee 79 10 4 26 Command CALibrate CURRent see ee ee ee ee ee ee ee de ee ee RR ee ee ee 79 10 4 27 Command CALibrate REFerence iese ee N ee ee ee Re ee ee 79 10 4 28 Command CALibrate REFerence iese dee ee ee ee ee ee ee ee ee ee ee ee 79 10 4 29 Command CALibrate OFFSet eese de ee ee ee ee ee ee ee ee ee 80 10 4 30 Command CALibrate OFFSet ee ee ee ee ee ee ee ee ee ee ee ee Re ee ee 80 10 4 31 Command CALibrate GAIN ee ee ee ee ee ee ee ee ee ee ee ee RR ee ee ee 80 10 4 32 Command CALibrate GAIN ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee ee 8l 10 4 33 Command CALibrate PASSword ees dee ee ee eene eene Ee ee ee nene ee esed enean 8l 10 4 34 Command CALibrate UNLOCK ee ee ee ee ee ee nne nnn ee ee nnn nentes sse enean 8l 10 4 35 Command CALibrate LOCK eese eene nennen hehe essen n RR ee ee ee 8l NN zelljlewiiemumm M e 12 1 CE Declaration itte eoo e o ree A re epos eene eo sv Pune eode voe EA EAE E T EA due tec eoo donee esee ves esos bae eso Ee any 84 12 2 dei e E EE 84 12 3 Standards Applied ionntas 84 13 REVISION HISTORY e eeeee eene eee eee eee e eee eese ee iarere riara D Page 5 of 85 GRIES Issue 1
89. sistor into the microK s database see section 3 7 2 then in the Settings tab select the channel to which the reference is connected in the Reference Channel box and the reference resistor entry in the Reference Resistor box Press the Single tab to see the measurements in numeric and graphical form Set the graph scales manually by making a note of the current Mean value and pressing Set Scales This opens the graph scales window Ensure that autoscaling is turned off press Autoscale to toggle autoscaling on off the status of autoscaling is shown by the adjacent indicator Use the ellipses buttons to set the y axis limits to be 0 005 C above and below the current mean value Use the radio and up down buttons to set the x axis to 5 minutes Page I5 of 85 GRIES Issue 1 01 Y Axis Channel ek Minimum e 4 259 Maximum 4 249 B A X Axis Scale Minutes ck Time Units Autoscale O Seconds Minutes JE OK Cancel Press OK to return to the main window The measurement system will now accumulate data and after 5 minutes the graph will begin to scroll to show the last 5 minutes of data Single Multi Settings Instrument Channel skis Clear Graph 4 2490000e0 4 2500000e0 4 2510000e0 4 2520000e0 4 2530000e0 4 2540000e0 4 2550000e0 4 2560000e0 4 2570000e0 4 2580000e0 Start S
90. ssseccccsceeeeceseseeeccssseceueeseseeeccssseeeuuensnseeecess 54 7 1 3 Voltage MEAS HEUTEN 55 RESA Zero Voltage EE 55 71 3 2 Voltage Span Chieek E 55 7 2 Adjusting Calibration sesse sees sesse ss se ee GE EE SR AG GE EA AG GE RA Ge Ge EE SS RA Ge Ge EE EE RA Ge Ge oesi soos ee Ge ee 56 7 2 1 Calibrate Master Current Source 57 7 2 2 Calibrating the 400 Q Internal Reference Resistor cesssecssseecesseecesseeeesseeeesseeeessneeenanees 57 Page 3 of 85 GRIES Issue 1 01 _ISOT CH 7 2 3 7 2 4 7 2 5 7 2 6 7 2 7 7 2 8 Calibrating the 100 Q Internal Reference Resistor A 58 Calibrating the 25 Q Internal Reference Resistor sesse esse ee ee ee ee ee 58 Calibrating the 10 Q Internal Reference Resistor A 58 Calibrating the Q Internal Reference Resistor iese esse esse ee ee ee 59 Calibrating Voltage Zeros inrer err erp EE N EE ER ON 59 Calibrating Voltage Spasie esse ke SeSe ERENS EN EKS Ge Ge Ge Ge SN gee ENDER Eg be SG ER RS RD by ep Ek eg ee eg ei 60 8 R 232 INTERFACE iss sesess giese e ed e 8 1 Establishing an RS232 Connection scccccscccscccsescsccccesesecesesesesesesesesesesesecesesesesesesesesesesesesesessscssssscseseees 62 9 GPIB TDI AC OS RE Imc PELO IU eae a ma IEE Tia ee ee POS NERONE ie 6 9 1 GPIB Address ord ieee ee soie or esos eto Saa ora o oro ree rose oe eoo eosdebet SE s obe oos seo Eee esso EE e bee eol osa s OE e os Us 65 9 2 Establishing a GPIB Connection
91. sult the microK achieves voltage offsets significantly less that 250nV 6 5 Inherent Stability The current reversals used to eliminate thermal EMFs from resistance measurements together with true 4 wire resistance measurement have the effect of ensuring an intrinsically stable zero with time and temperature The voltage at the amplifier input when measuring a short circuit will be the same whichever current direction is used The process of averaging the measurements therefore yields zero with uncertainty determined by the system noise In a similar way the substitution technique means that the measurement system is also inherently stable at unity ratio since the voltages measured for a reference resistor and thermometer of the same value will be identical There is after all no difference between these two measurements apart from the fact that they are taken at slight different times The system noise will again determine the uncertainty of this unity ratio measurement Page 50 of 85 GRIES Issue 1 01 _ISOT CH 6 6 Eliminating Self Heating Effects Although the sense currents used with SPRTs are small they can still generate self heating errors of several mK The most accurate SPRTs typically have very lightly supported elements so the self heating effect is ironically worst in those SPRTs designed for the most accurate measurements The microK includes individual keep warm current sources for each of the three input
92. t signal is subtracted from the output of a bit DAC before being filtered by a series of cascaded integrators The signal then passes to a bit ADC that drives the DAC and forms a feedback loop Integrators OUTPUT VALUE mee p pe j 1 Bit ADC 1 Bit DAC Conventional S A ADC Digital Filter The extremely high low frequency loop gain of the cascaded integrators ensures that the input signal is balanced against the output of the DAC so that the average value of the bit data stream from the DAC equals the input signal A low pass digital filter is then used to extract the converted value from the bit data stream Another way of viewing the operation of a X A ADC is to consider what is happening in the frequency domain The over sampling used in X A converters means that the quantisation noise caused by the bit ADC is spread over a wide bandwidth whereas the signal we are looking for is unaffected by this over sampling The digital filter selects the narrow bandwidth of the required signal The amount of quantisation noise in this bandwidth is relatively small because the over sampling spreads the noise power over such a large bandwidth Page 46 of 85 GRIES Issue 1 01 _ISOT CH The quantisation noise on the converted signal can be reduced by increasing the sampling rate but it becomes increasingly difficult to maintain performance as the clock rate of the system increases Another way to reduce the noise wou
93. tage from a thermocouple you should always use the most sensitive voltage range 0 125V since this provides the lowest uncertainty and no thermocouple output will exceed this range You can use the following command sequence SENS FUNC VOLT SENS VOLT RANG O I SENS CHAN READ The microK will then report the measured voltage for example 1 12999999E 007 The following command performs the same measurement MEAS VOLT I 0 1 10 4 SCPI Commands The microK supports the following commands IDN RST SENSe FUNCtion ON FUNCtion ON CHANnel CHANnel NOLTage DC RANGe UPPer RANGe UPPer FRESistance REFerence REFerence fj ISUT CH lt function gt lt channel gt voltage range gt reference channel Page 70 of 85 Issue 1 01 _ISOT CH RANGe UPPer RANGe UPPer RATio REFerence REFerence RANGe UPPer RANGe UPPer INITiate IMMediate ALL FETCh SCALar READ SCALar READ lt channel gt MEASure SCALar VOLTage DC lt channel gt FRESistance lt channel gt REFerence lt reference gt RATio lt channel gt REFerence lt reference gt SOURce CURRent TEST CURRent CALibrate CURRent REFerence lt reference gt REFerence lt reference gt OFFSet lt channel gt OFFSet lt channel gt GAIN GAIN PASSword UNLock LOCK resistance range gt current lt denominator channel
94. tandard 0 note Voltage 3ppm year Resistance lt 2s Is using the RS232 or GPIB interfaces Voltage lt Is 0 5s using the RS232 or GPIB interfaces PRTs ITS 90 Callendar van Dusen Thermocouples IEC584 1 1995 B E J K N R S T L and gold platinum Thermistors Steinhart Hart Page 82 of 85 Issue 1 01 _ISOT CH Sensor Current Keep Warm Current Cable Length Internal Standard Resistors Input Connectors Interfaces Display Operating Conditions Power Size Weight Notes 0 10mA in 3 ranges O IlmA 0 4 of value 70nA resolution 28nA ImA 0 4 of value 40 7ZUA resolution 280nA I0mA 0 4 of value 7UA resolution 2 8uA O 1OmA 20 496 of value 7UA resolution 2 8uA 30m maximum 10Q per core or OnF shunt capacitance IO 40 1 TCR lt 0 6ppm C typical stability lt 5ppm year 10Q 0 1 TCR lt 0 6ppm C typical stability lt 5ppm year 25 100 400 O 0 1 TCR lt 0 3ppm C typical stability lt 5ppm year Cable Pod connectors for 4mm plugs spades or bare wires Contact material gold plated tellurium copper RS232 9 600 baud GPIB USB 1 1 host 163mm 6 4 VGA 640 x 480 colour TFT LCD 15 30 C 50 85 F 10 80 RH for full specification 0 40 C 32 105 F 0 95 RH operational 88 264V RMS 47 63Hz Universal 20W maximum 5A RMS maximum 520mm x 166mm x 300mm 20 5 x 6 6 x 11 9 WxDxH 12 4kg 27Ib The
95. thermometer Max Temperature box This box contains the maximum operating temperature for the selected thermometer If you are creating a new thermometer entry the ellipses button by the box becomes active Press this button to open a Numeric Keypad window and enter the maximum operating temperature for the thermometer Conversion box This box contains the conversion to temperature units used for the selected thermometer If you are creating a new thermometer entry use the up down buttons to select the required conversion Coefficients button This button opens a window that allows you to enter the coefficients required for the temperature conversion In the case of ITS 90 or thermocouples these are the coefficients for the deviation function the base conversion coefficients are fixed Conversion Name Conversion Type ITS90 is ITS 90 Lal R 0 01 25 5 i Coefficients for T O 019C Coefficients for T 0 019C a D a 0 p 0 p l0 CEET OK ween 222 0 New button Press this button to make a new thermometer entry into the microK s database ellipses and up down buttons by the boxes then become active Page 31 of 85 GRIES Issue 1 01 _ISOT CH Delete button Press this button to delete the selected thermometer or the current entry for a new thermometer from the database OK button Press this button to confirm
96. to eliminate the thermal EMFs The limitation is then the thermal EMFs generated by the devices used to implement this reversal 6 4 Solid State Switching One of the most common sources of failure in instruments of this complexity is the contacts in switches relays connectors and potentiometers For this reason the microK was designed to have no switches apart from the on off switch mechanical relays or potentiometers The switches normally used for the operator interface have been replaced with a combination of an industrial grade touch screen over a full colour VGA LCD making the instrument both reliable and easy to use The internal connectors are limited to three ribbon cables with gold plated contacts for signal interconnections plus a small number of connectors for the AC power and internal DC supply Conventional instruments of this type use mechanical relays for some or all of the signal routing The microK uses only solid state switching The thermal EMFs from the metal silicon junctions in solid state switching devices are potentially higher than for mechanical relays under the same temperature gradient However the very small size of the die within the semiconductor devices means that there would be little opportunity for thermal gradients giving them a strong advantage over their mechanical counterparts In practice the thermal EMFs from solid state switching are significantly less than even the best mechanical relays As a re
97. to filter your electrical supply into the laboratory especially if other heavy electrical machinery is being used nearby on the same supply the microK has very good immunity to electrical noise conducted along the electrical supply but other equipment in your laboratory may be more sensitive It is worth avoiding using sources of electrical signals or noise in your laboratory Examples include furnaces with triac controls especially those that chop the electrical supply part way through a cycle better controllers switch only at the zero crossing point to chop whole cycles only mobile phones the microK is not significantly affected by mobile phones but other equipment may be more sensitive Page 45 of 85 GRIES Issue 1 01 _ISOT CH 6 The microK Technology The microK uses a number of new technologies and measurement techniques to achieve performance that has not previously been available with potentiometric measurement systems 6 1 The ADC The ADC Analogue to Digital Converter in a precision instrument is the measurement engine Its performance is the starting point for achieving low measurement uncertainty The microK uses a completely new type of ADC which was designed specifically for this product It is based on the well established X A sigma delta technique but uses multi bit feedback to achieve performance that is not achievable with conventional A ADCs In a conventional X A ADC the analog inpu
98. to the amplifier changes between the two measurements and will lead to an error at the input to the ADC In order to eliminate this source of error the microK uses a substitution topology in which there is a single point of measurement in the system into which the SPRT and Reference Resistor are switched alternately Resistor Reference Amplifier Substitution Measurement Topology This adds complexity and cost to the design but ensures that there is no change to the common mode signal between the measurement of the reference resistor and the thermometer This approach would normally however increase the demands on the current source In the conventional topology the current Page 48 of 85 OSE LES Issue 1 01 _ISOT CH is common to both the reference resistor and the thermometer In the substitution topology the voltage at the output of the current source changes between the measurement on the SPRT and the Reference Resistor and the current source must accommodate this change without any significant change to the sense current The current source in the microK has a very high output impedance such that the sense current will not change significantly between the measurement of the reference resistor and the thermometer In addition the whole measurement system is actively guarded so that both the voltage at the output of the current source and the common mode voltage across the device being measured do not change
99. ton to open an Alpha Numeric Keyboard window and enter a name The Shift key toggles the alpha keys between upper and lower case Serial Number box This box contains the serial number of the selected thermometer If you are creating a new thermometer entry the ellipses button by the box becomes active Press this button to open an Alpha Numeric Keyboard window and enter a serial number The Shift key toggles the alpha keys between upper and lower case Calibration Due box This box contains the date when calibration is due for the selected thermometer If you are creating a new thermometer entry the ellipses button by the box becomes active Press this button to open a Date Entry window and enter a date The ellipses buttons by the Day Month and Year boxes in the Date Entry window open a Numeric Keypad window Dates are checked for validity including leap years for dates up to 31 December 2099 Page 30 of 85 GRIES Issue 1 01 _ISOT CH Thermometer Type box This box contains the type of thermometer PRT Thermocouple or Thermistor If you are creating a new thermometer entry use the up down buttons to select the thermometer type Min Temperature box This box contains the minimum operating temperature for the selected thermometer If you are creating a new thermometer entry the ellipses button by the box becomes active Press this button to open a Numeric Keypad window and enter the minimum operating temperature for the
100. ure failure The USB Connector The USB connector is primarily intended to allow you to connect a USB flash drive store measurement results and transfer these to a PC The flash drive may also be used to backup the databases of thermometers reference resistors and instrument configurations for your microK Other USB devices such as a mouse keyboard keypad or USB hub may be connected to the USB port and used provided they utilise the standard class drivers provided with the Windows CE operating system incorporated in your microK On the rear panel of your microK you will find the electrical supply connector power switch fuse module plus the interface connectors that allow you to connect your instrument to a PC The RS232 and GPIB ports allow you to control the instrument and take measurements from a PC with your own software see section 8 The command protocol employs the widely used SCPI format see section 9 for details The USB connector is provided for future expansion and should not be used on this model Page 10 of 85 GRIES Issue 1 01 IEC 60320 1 Power Supply Fuse Connector USB B En Connector GPIB Switch unused Connector RS232 Connector Page of 85 mE Issue 1 01 _ISOT CH 2 Making a Measurement Tutorials The operator interface is powered by the Windows CE operating system With the widespread use of Windows applications on PCs driving your microK should be fairly intuitive As with most Windo
101. ws applications it is possible to navigate your way through a process using a number of different paths so rather than describe each window and the function of each button and then leaving you to work out how to operate the instrument we provide you with a number of tutorials that illustrate common applications Even if these do not describe your application it is worth working through one of them since it will provide you with a broad understanding of the wide range of features available on your microK A traditional description of the function of all the features provided by the operator interface is given in section 3 2 1 Measuring Temperature with a Calibrated SPRT From startup press Resume to restart your microK Isothermal Technology microK 250 S N 14 P702 Firmware v3 21 Loader v1 9 5 Software v1 4 29 Language v1 4 34 microsKanners detected none Resume Measurement system initialised Before making any measurement you will have to enter information about the thermometer into the microK s database When the main window opens press the Instrument tab Page 12 of 85 GRIES Issue 1 01 Single Multi Channel We IL iiy Clear Graph Start Save Set Scales m o Dr Hu bk OO 4 OD o Iz 0 0 Times In the Instrument tab press Edit Thermometers Single Multi Settings Instrument System Cali

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