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1. 50 000000 8 2 6 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 1 SENS FUNC volt and SENS VOLT RANG 0 1 use INIT 8 2 6 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 1 using the commands shown in the example in section 8 2 6 17 will respond to FETC with something similar to 1 70000000E 008 8 2 6 19 Command 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 Example a microK that is connected to a short circuit on channel 1 and has been configured to make a voltage measurement using SENSe commands such as Page 82 of 90 Issue 1 01 SENS CHAN 1 SENS FUNC volt and SENS VOLT RANG 0 1 will respond to READ with something similar to 1 70000000E 008 8 2 6 20 Command MEASure VOLTage Format MEASure SCALar VOLTage DC lt 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 comma
2. 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 microK Data 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 37 of 90 Issue 1 01 3 7 8 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 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 7 before using this feature 3 7 9 Backup 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 sto
3. User Manual Applies to Software version 1 2 94 Firmware version 2 004 ISUT CH Isotech North America 158 Brentwood Drive Unit 4 Colchester VT 05446 Phone 802 863 8050 Fax 802 863 8125 sales isotechna com www isotechna com CONTENTS 1 INTHODUGTIONL is nui ad oae rcs tate rano niea deua uu eus us Vu cer Esa uds 6 1 1 UBDACEKIBP 5 seite eei eei ien IE IE utu E ere EUR Mose teu Ue UE eT A 7 1 2 BS AGC Y can sever cle non dii etude cda ao nice tp a accra cde eee 7 1 3 Powermpg Up Your BilCFOK c oet cece eres ceca aE EXE UE ENS SAA A SEREEN 9 1 4 A Quick Four of Your miCEOK iiis rete deese a eve voa d ep ao auge ao de e edet et eue cs doa eade esse saos TaN 9 2 MAKING A MEASUREMENT TUTORIALS 12 2 1 Measuring Temperature with a Calibrated SPRT eee eee eee eene 12 2 2 Measuring Temperature with a Thermocouple ccce ee eee ee ee eee eee ee 16 3 DRIVING YOUR MICRON hix racu renun amp nS Eua Yen ah uen due as i naa eaa 20 3 1 PEP OG UCLON M 20 3 2 The Startup W Ui OW e 20 3 3 The Main Wind OW a 21 3 4 The Sin Gl Wa o 22 3 5 The Multi e e 25 3 6 The Settings ICT ee idisse didai aaaea aai ii anaana aaia 27 3 7 The Instrument Gab rc P 30 3 7
4. 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 87 of 90 Issue 1 01 9 Specification Ranges Resistance Thermometers Accuracy PRTs Accuracy Thermocouples Resolution Stability Measurement Time Temperature Conversions Sensor Current 0C to 500k Q Thermocouples 125mV uUK400 0 4ppm maximum over whole range for SPRT with Ro 2 2 50 equivalent to 0 1mK at 0 C or 0 4mK over full range 1ppm maximum over whole range for SPRT with Ro 0 250 UK800 0 8ppm maximum over whole range for SPRT with Ro 2 2 50 equivalent to 0 2mK at 0 C or 0 8mK over full range 2ppm maximum over whole range for SPRT with Ro 0 250 250nV at 20mV equivalent to 0 01 C for Gold Platinum thermocouple at 1000 C Voltage uncertainty Resistance 0 01ppm of range Voltage 2nV 125mV range Resistance excluding resistance standard O note1 Voltage 3ppm year Resistance lt 2s 1s using the RS232 interface Voltage lt 1s 0 5s using the RS232 interface 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 0 10mA in 3 ranges 0 1mA 0 4 of value 70nA resolution 28nA 1mA 0 4 of value 0 7uA resolution 280nA 10mA 0 4 of value 7uA resolution 2 8uA Page 88 of 90 Issue 1 01 Keep War
5. M orm milli 10 K ork kilo 10 MA orma mega 10 Page 73 of 90 Issue 1 01 8 2 5 Making Measurements using SCPI Commands The microK includes a measurement system controlled by a microprocessor and a touch screen user interface controlled by an Intel PXA processor The measurement system has 2 RS232 connections one 1s the RS232 connector on the rear of the microK and the other 1s to the PXA processor The measurement system is controlled by SCPI commands from either of these ports It makes no distinction between commands received on the user RS232 interface and those from the PXA processor If you want to make measurements using the SCPI commands on the RS232 interface you first need to prevent commands being sent from the internal PXA otherwise these commands may interfere with your measurements by changing the measurement settings The easiest way to do this is to repower 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 commands will be sent to the measurement system 8 2 5 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 Go S HE Gs GE If you want to measure a 25 5 SPRT up to a maximum resistance of 3
6. Page 4 of 90 Issue 1 01 8 2 6 33 Command CALibrate UNLOock eene 87 8 2 6 34 Command CALibrate LOCK eee 87 Q SPECIFICATION Q ccccceccececeecececeeeececeeneeeseceseececeseeeeseeeeeeeuseeeeeaes 88 10 APPROVALS deren ctii isse nisus a ered beaten 90 10 1 CE Declaratio xo nune ii ace vetere to Leder Nee oes ovis deiuia edocs ime pasados potus 90 10 2 Standards AP DUNC E Im 90 Page 5 of 90 Issue 1 01 1 Introduction The microK 400 and micro 800 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 re
7. 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 reference resistor If you are creating a new reference resistor entry the Page 34 of 90 Issue 1 01 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 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
8. 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 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 Choose one of the measurement channels if you want to measure the temperature of the reference junction with a Page 28 of 90 Issue 1 01 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 1s 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 Current b
9. 2 2 but configure the microK to measure a Default PRT at ImA against the internal 100Q reference on the 125Q range on channel 1 7 1 2 4 25 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 1mA against the internal 25Q reference on the 125Q range on channel 1 7 1 2 5 10 O Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 10 to channel 1 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 400 internal reference see section 7 1 2 2 but configure the microK to measure a Default PRT at 5mA against the internal 10Q reference on the 25Q range on channel 1 7 1 2 6 1 QO Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 1Q to channel 1 Ideally this should be a Wilkins resistor with a recent traceable calibration certificate Configure the microK to measure a Default PRT at 1OmA against the internal 1Q reference on the 13 range on channel 1 other channels disabled Use 1 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 Sin
10. 80 for temperatures up to 31 C decreasing linearly to 50 RH at 40 C Equipment is for operation at installation category II transient voltages and pollution degree Il 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 rating marked on the rear panel Ifareplacement 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 13kg 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 tripp
11. Edit Thermomete Seieren si etin mte Ctm Ute erecta eitis vedo 3 3 422 Echt Re SISCOLS A catches pa eset autores nM i I CM DEED 33 3 7 3 CAMO PATON ioira aean Coen each scasienes neti a osa Doc boe REESE 35 3 7 4 Update SOPGAte duo Deddoa o ah in eben Ab te o dodi 35 3 7 5 Chango PASC WONG ota eaestasdesetedi ine Sind acude edt use uude veau 36 3 7 6 SEU Date and TIME quisa once ius epe Mel Soa Ses oett do dpa ut iso ded 36 3 7 1 Backup Dalipi a ea dahl e one saape Lf cM 37 3 7 8 Clear Data File Sos o b De Derim Dt rcm tV UR 38 3 7 0 Back p COMM UtatEOD saciid eewoeh evi sus N Dese Su ba Po aie 38 ARIO Load onPIoutdtlolvo secu sence to torni adeo e horn ume 38 3 8 Using the Thermometer Database eere tee ee tee erae bao eben enu e EURO SER SEES Nx Ha eHe e eua Io eae n e S Nee e 39 3 9 Using the Reference Resistors Database ecce ecce eee ee eee eee e e ee eee ee e teet ee 39 3 10 Saving Instrument Configurations ccce eee e eee e ee eee e ee eee ee eee eee etes tees esee esse sssssssaae 40 3 11 Password Protection of Key Settings ccccssssssssssssssssssssssssssssssssssssssssssssssssssssseees 41 4 CONNECTING THERMOMETER SENSORS 42 Page 2 of 90 Issue 1 01 4 1 The Cable Pod Connectors cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccsccecs 42 4 2 Connecting ER Ts d WI aiii er Dr EC n HEY CU E PE de ESTERNI NOE I
12. Valid forms of this command include MEAS VOLT MEASURE SCALAR VOLTAGE DC 8 2 2 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 Page 72 of 90 Issue 1 01 In addition to the 3 input channels on the front panel which are assigned the suffices 1 2 and 3 the internal reference resistors are specified using numeric suffices as follows channel Internal reference resistor 201 1Q 202 10 Q 203 25 QO 204 100 Q 205 400 Q In order to measure the voltage on channel 3 the command used would be MEAS VOLT3 8 2 3 Parameters 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 on channel 2 using the 100 ohm range and a sense current of ImA would be MEAS FRESI REF2 100 1 8 2 4 Units 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 1 The following prefixes are available prefix name factor Norn nano 10 Uoru micro 10
13. 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 38 400 Baud for further details of how to connect a PC to your microK see section 8 1 Page 62 of 90 Issue 1 01 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 respond with a string in the form Isothermal Technology microK 400 06 PP006 firmware version 1 2 The calibration of your microK is password protected Unlocked the calibration to allow calibration adjustment using the command CAL UNL password where password 1s the calibration system password NOT necessarily the same as the password used in the touch screen operator interface The password 1s initially set to 1234 but should be changed for security reasons see section 8 2 6 32 You can now use the SCPI commands see section 8 2 6 detailed below to adjust the microK s calibration 7 2 1 Calibrate Master Current Source The microK s current source has 3 ranges 0 0 1mA 0 I1mA and 0 10mA The tolerance between the ranges is sufficiently
14. 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 Startup Window contains the Resume button Page 20 of 90 Issue 1 01 Isothermal Technology microK 21 253 S N O6 PPOO7 firmware version 2 00 Resume Measurement system initialised 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 1s 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 1s presented with the Main Window Page 21 of 90 Issue 1 01 Single Multi Settings Instrument B Channel DD oem mou Mean of last 100 47 77900 47 77800 47 77700 47 77600 47 77500 47 77400 47 77300 47 77200 47 77100 47 77000 1 800 1 850 1 900 1 950 2 000 2 050 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
15. certificate Conversion Name Conversion Type mw Jj m Roo Bs Eor beooc woo B 96962868 eooc oor D Jagsoote w001 J 10846807 wecoscs 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 1 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 1 Use the up down buttons by each box to select the required settings Page 14 of 90 Issue 1 01 Single Multi Settings Instrument Channel Units Thermometer Current mA e SPRT 1 o 1 0000 ad Conversion Samples per Reading s no 8 2 1e Range Ohms Readings in Rolling Statistics js 1s she 15 Reference Channel Reference Resistor Interna 100R o i 100 0000 The sense current is assumed to be 1 mA 1n 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 1 see section 4 2 for details on how to connect 4 wire PRTs The tutorial assumes you are using the internal 100 reference resistor To use an external reference resistor first enter information on the resistor into the microK s database see section 3 7 2 then i
16. 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 1s therefore even more important to use a screened cable and connect this to the screen terminal on the microK than when using PRTs Page 46 of 90 Issue 1 01 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 1s 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 have 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
17. 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 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 1s intended for use in temperature metrology its base measurements are electrical resistance or voltage The limited sensitivity of Page 47 of 90 Issue 1 01 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 25Q SPRT a ImK temperature uncertainty corresponds t
18. 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 8 2 6 11 but has its sense current set to 10mA would respond to the command SENS FRES RANG with 50 000000 8 2 6 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 INITiate or READ commands Example to select channel 2 as the reference channel for the next resistance ratio measurement use SENS RAT REF 2 Page 80 of 90 Issue 1 01 8 2 6 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 8 2 6 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 5 V and depends on the s
19. small that it 1s only necessary to calibrate the ImA range in order to achieve the full performance specification Connect a calibrated ammeter or DMM across the current terminals of channel 1 and connect both the sense inputs to the red current terminal Send the command TEST CURR 1 to your microK from Hyperterminal this forces the microK to source 1mA on channel 1 Measure the current and then type in the command CAL CURR current where current is the measured value Page 63 of 90 Issue 1 01 Now type in TEST CURR 1 again to update the current source The ammeter should now read 1mA 0 0003mA Check the other current ranges by typing in the following commands and checking that the current is within the given limits command current limits TEST CURR 0 1 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 1 0 9975 to 1 0025 mA TEST CURR 10 0 975 to 10 025 mA 7 2 1 1 Calibrating the 400 Q Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 100 to channel 1 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 ImA against the internal 400Q reference on the 500Q range with channel 1 other channels disabled Set the units to ratio Rt Rs with 1 sample per reading and 100 readi
20. 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 5us so Page 51 of 90 Issue 1 01 the 0 2ppm linearity achieved with the A ADC corresponds to a timing accuracy of Ips or about the time it takes for the electrical signals in the control system to travel 0 3mm 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 DAC 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 1s its speed The implementation used in the microK provides conversions to full accuracy in 100ms This together with the use of solid state switching allows for a very
21. 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 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 1n 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 the reference resistor used in the resistance measurement either one of the internal reference resistors or the channel to which an external resistance standard 1s connected 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
22. 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 COM14 Properties ax Bits per second 3600 Mi Data bits 8 Y Parity None vi Stop bits 1 v Flow control None v 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 this icon to open an RS232 connection with your microK Page 70 of 90 Issue 1 01 Type IDN into Hypertemrinal 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 400 06 PP006 firmware version 1 2 This confirms that you have successfully established an RS232 connection with your microK 8 2 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 8 2
23. 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 10 rather than having to enter all the setting for that particular measurement configuration individually Page 40 of 90 Issue 1 01 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 alleviated some of the concerns that accreditation bodies have about the integrity of measurements You need to enter the password to perform the following tasks 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 G5 G5 G5 G5 G5 Go Page 41 of 90 Issue 1 01 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 grad
24. 0 against the internal 100 reference the maximum resistance that the measurement system sees is 100Q To make this measurement using a 1mA sense current you can use the following command sequence SENS FUNC FRES CURR 1 SENS FRES RANG 100 1 SENS CHAN 1 SENS FRES REF 204 READ Page 74 of 90 Issue 1 01 The microK will then report the measured resistance for example 42 5250637862E001 The following command performs the same measurement MEAS FRESI REF204 100 1 8 2 5 2 Measuring 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 make the measurement If you want to measure the voltage 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 0 1 SENS CHAN 1 READ The microK will then report the measured voltage for example 1 12999999E 007 The following command performs the same measurement MEAS VOLTI 0 1 Page 75 of 90 Issue 1 01 8 2 6 SCPI Commands The microK supports the following commands IDN RST SENSe FUNCtion ON FUNCtOon ON CHANnel CHANnel VOLTage DC RANGe UPPer RANGe UPPer FRESistance REFerence REFeren
25. 1 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 71 of 90 Issue 1 01 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 1f the last letter is a vowel To indicate this the notation 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
26. 5V 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 125mV range Page 78 of 90 Issue 1 01 8 2 6 8 Command 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 8 2 6 7 would respond to the command SENS VOLT RANG with 0 125 8 2 6 9 Command SENSe FRESistance REFerence Format SENSe FRESistance REFerence reference channel 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 2 as the reference channel for the next resistance measurement use SENS FRES REF 2 8 2 6 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 2 as the reference i
27. E 42 4 3 Connectie PR TS 5 IEG oes eed exea exte ua NEN EIE het ev un vu NE VS VR RR E RU LESEN E NEUE UE 43 4 4 Connecting PRTS 2 WIEe iie eee eere eene deoa naa 6o nn nonae erae ee aen u ea ee ua epe o ene Nene eee uana ne socis aeos epe e een 43 4 5 Connecting Thermocouples external Ice Point or WTP e ee eere 44 4 6 Connecting Thermocouples using RJ compensation eee ee eere 45 4 7 Connectie Thermistorls 28 ore erri E Ee PEN OE D Rea va E eU un O REVUE ERE MERE RAE 45 5 GOOD PRACTICE GUIDELINES eere 47 5 1 Looking After VY Our MICrok soci os ccctvssscccsctsvssvscectssecswaceenscessvebesseceudasstaccceessendbusssietecsoeys 47 5 2 Making a Good Electrical Measurement ccce eee eee eee ee eee eee e eee eee eate e ee eee 47 6 THE MICROK TECHNOLOQY eren nnne nnns 50 6 1 PG ADD sasaki cask a 50 6 2 PUDSECU ION Ene M 52 6 3 Minimising Therma EMES sisccisssscccesessdesntesvesesacvesendasacuscaueseseeveessiesseeconsastsaneecsesseusteeues 54 6 4 Solid State SWC D 55 6 5 Inherent Stability d 55 6 6 Eliminating Self Heating Effects eee eee Lecce eee eee ee ee eee ee teet ette esee 56 CALIBRATION saoscc dices eset a ec
28. EF203 R25 Where R25 is the value calculated for the 25 internal reference 7 2 1 4 Calibrating the 10 Q Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 10 to channel 1 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 400 internal reference see section 7 2 1 1 but configure the microK to measure a Default PRT at 5mA against the internal 10Q reference on the 25 range with channel 1 The command to adjust the value assigned to the 10Q internal reference 1s CAL REF202 R10 Where R O is the value calculated for the 10Q internal reference Page 65 of 90 Issue 1 01 7 2 1 5 Calibrating the 1 Q Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 1Q to channel 1 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 1 1 but configure the microK to measure a Default PRT at 10mA against the internal 1Q reference on the 13Q range on channel 1 The command to adjust the value assigned to the 1Q internal reference is CAL REF202 R Where R is the value calculated for the 1Q internal reference 7 2 2 Calibrating Voltage Zeros Short out the 4 measurement terminals on all 3 channel
29. FACE cccececsccececnececenneescncneneeecncnseecncnsnseesnensensens 69 Establishing an RS232 Connection sssescsosssssessceceececococssssssssesecccecococsssssssseseeceeoesssssso 69 SCPI C mtmalid Seba eoe eee eet o eiriaa o ee oa Ra sevo ae aa Yu Vr oa aoa enano a PES VEN ToU EEEE FPE tia 71 8 2 1 SCPLComiudid SUNCU ss 4i e sien cacbosda met see eso f reb ooa 71 8 2 2 SCPI Numeric Suffices eese eene eene ense eser ene 12 8 2 3 PO aa nM EL EL de DM AN 73 8 2 4 BU SUL E E E RE TO teat at sce oan laser EE A mason ea 73 8 2 5 Making Measurements using SCPI Commands 74 8 2 5 1 Measuring Resistance using SCPI Commands 74 8 2 5 2 Measuring Voltage using SCPI Commands 75 8 2 6 SC PEC OrFnmdtdsaeseieee een ase Sueton OU o uahon Wer dieta eer dbtee sends 76 S280 Commands IDN sie octets repente itta tede Dativo dmado 77 9 220 2 Command RS T oues else a a 77 8 2 6 3 Command SENSe FUNCOION 20 cece eene 77 8 2 6 4 Command SENSe FUNCION 0 cece ecceeceseeseeen eee 77 8 2 6 5 Command SENSe CHANncel eee eene 78 8 2 6 6 Command SENSe CHANnel eee eee 78 8 2 6 7 Command SENSe VOLTage RANGe s eeeeeeeee 78 8 2 6 8 Command SENSe VOLTage RANQGe eere 79 8 2 6 9 Command SENSe FRESistance REFerence 79 8 2 6 10 Command SENSe FRESistance REFere
30. PPOO7 firmware version 2 00 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 Settings Instrument Char e 19 ccon un e O r e ih to Ul a t0 X e 0 0 Time j s In the Settings tab disable channels 2 and 3 this will speed up measurements on channel 1 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 1 Use the up down buttons by each box to select the required settings Page 17 of 90 Issue 1 01 Single Multi Settings Instrument Channel Units Thermometer e Default Thermocouple o Conversion Samples per Reading meeNTememwe 12 ola ell Range V Readings in Rolling Statistics sm is sje 1o Reference Junction The reference junction is assumed to be an ice point in this tutorial It can be set to the water triple point or to use a temperature measured by one of the other channels see sections 3 6 and 4 6 if using r
31. an cause high common mode voltages on any thermometer in the furnace Whilst the microK is deigned to reject common mode DC and AC signals at both 50 and 60Hz it 1s Page 48 of 90 Issue 1 01 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 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 only whole cycles mobile phones the microK is not significantly affect
32. 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 except for the 1 ohm standard which is not available in an hermetic pack 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 The 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 1 mA 0 ImA and 0 10mA Check these by connecting a calibrated ammeter or DMM across the current terminals of channel 1 and connecting both the sense inputs to the red current terminal Checking the master current source involves connecting a PC to your microK using a null modem RS232 cable and sending commands to it from Page 57 of 90 Issue 1 01 Hyperterminal part of the standard Windows operating system installation or another terminal emulator For furth
33. 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 l X2 X10 X40 Page 86 of 90 Issue 1 01 The parameter polarity 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 8 2 6 32 Command CALibrate PASSword Format CALibrate PASS word old password password 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 1234 ABCD ABCD 8 2 6 33 Command CALibrate UNLock Format CALibrate UNLock password Unlocks the microK to allow calibration 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 8 2 6 34 Example to unlock enable the calibration adjustment on a microK with the default password 1234 use CAL UNL 1234 8 2 6 34 Command
34. atibility 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 10 2Standards Applied The following standard have been applied in assessing compatibility with the requirements for CE marking and for FCC compliance Conducted Emissions EN61326 1997 amp CFR47 2005 Radiated Emissions EN61326 1997 amp CFR47 2005 Conducted Immunity EN61326 1997 Radiated Immunity EN61326 1997 Electrical Fast Transients EN61326 1997 Electrostatic Discharge EN61326 1997 Surge EN61326 1997 Voltage Dips amp Interruptions EN61326 1997 Harmonic Currents EN61000 3 2 2000 Flicker EN61000 3 3 1995 Electrical Safety EN61010 1 2001 Page 90 of 90 Issue 1 01
35. 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 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 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 90 Issue 1 01 Input Touch Screen USB Terminals amp Display Connector Input Terminals The input terminals accept 4mm plugs spades or bare wires The current I and voltage sense V terminals are spaced on 97 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 mount
36. 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 To import the data into Microsoft Excel simply click open within Excel select All Files under File Types browse to the required file on the USB flash drive and then click Finish in the Text Import Wizard that appears 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 or readings in the statistics 1s set in the Settings tab for each of the channels that are enabled Page 25 of 90 Issue 1 01 Single Multi Settings Instrument e se 92 9963 _ Om 99 996291 Mean of last 100 0 000047 Sp Channel 2 Volts 0 000000122 Mean of last 100 0 000000025 5D Mean sd Clear buttons Press the Clear button to clear reset the statistics for each channel The displayed values are updated as new 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 1s The reading rate for three PRTs with one sample p
37. ce RANGe UPPer RANGe UPPer RATio REFerence REFerence RANGe UPPer RANGe UPPer INITiate IMMediate ALL FETCh SCALar READ SCALar MEASure SCALar VOLTage DC lt channel gt FRESistance lt channel gt lt function gt lt channel gt lt voltage range gt lt reference channel gt lt resistance range gt lt current gt lt denominator channel gt lt resistance range gt lt current gt lt voltage range gt REFerence lt reference gt lt resistance range gt lt current gt RATio channelz REFerence SOURce CURRent TEST CURRent CALibrate CURRent REFerence lt reference gt REFerence lt reference gt gt OFFSet lt channel gt gt OFFSet lt channel gt GAIN GAIN PASS word UNLock LOCK resistance range gt lt current gt lt current gt lt current gt lt actual current gt lt actual resistance gt lt offset gt gain polarity adjustment ain polarity old password password password password A detailed description of each command follows Page 76 of 90 Issue 1 01 8 2 6 1 Command IDN Format IDN Reports information on the microK in 4 comma separated fields manufacturer model serial number firmware version G5 SH Example for a microK 400 with serial number 261067 1 using firmware version 1 20 the microK responds to IDN with Isothe
38. ce resistors adjust instrument settings time date and passwords or update the software Page 30 of 90 Issue 1 01 Single Multi Settings Instrument System Calibration o9 x Edit Thermometers Edit Resistors Set Date and Time Calibration Backup Data Update Software Clear Data Files Backup Configuration Change Password Load Configuration 3 7 1 Edit Thermometers Press the Edit Thermometers button to create edit or delete a thermometer in the database You will be prompted to enter the password in order to proceed e SPRT 3 o Thermometer Thermometer Name Thermometer Type errs 5 ee le Manufacturer s Name Min Temperature Boen FR e Serial Number Max Temperature 061130 m 1000 m Conversion Calibration Due supo ojmm 8 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 Page 31 of 90 Issue 1 01 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 ma
39. d 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 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
40. dy 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 T d T d OOnNDAFRWDND OOnNDOAFRWDND Shel O QO Shell Null Modem Cable The format for the RS232 interface is as follows Baud Rate 9 600 Start Bits 1 Stop Bits Parity Bit none Page 69 of 90 The microK has a 256 byte circular receive buffer If the buffer becomes full it de asserts RTS connected to CTS on your PC through the null modem cable to prevent further data being sent If the PC continues 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 AccessorieslCommunications folder If you have installed a minimum laptop or custom configuration without this component for your Windows operating system you may need to install Hypertermianl 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
41. e thermocouples The connectors accept 4mm plugs bare wires or spade terminations Additionally they are spaced on 19mm 34 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 The Cable Pod M 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 ght level in order to ensure that they are not subject to undue wear or premature failure This is all that 1s required electrically do not try to use the connector to provide strain relief or tension 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 Page 42 of 90 Issue 1 01 The top terminal should be connected to the screen of the SPRT s lead to minimise electrical noise picked up by the wires 4 3 Connecting PHTs 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
42. ed by mobile phones but other equipment may be more sensitive Page 49 of 90 Issue 1 01 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 amp A sigma delta technique but uses multi bit feedback to achieve performance that is not achievable with conventional X A ADCs In a conventional X A ADC the analog input signal is subtracted from the output of a I bit DAC before being filtered by a series of cascaded integrators The signal then passes to a 1 bit ADC that drives the DAC and forms a feedback loop Integrators Conventional X A ADC 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 1 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 1 bit data stream Page 50 of 90 Issue 1 01 Another way of viewing the operation of a 2 A ADC is to consider wha
43. ed in front of the display so that you can control the instrument by simply touching the buttons displayed on the LCD The touch panel 1s 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 premature 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 Page 10 of 90 Issue 1 01 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 port allows 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 8 2 for details The USB and GPIB connectors are provided for future expansion and should not be used on this model IEC 60320 1 supply Power Connect
44. ee eee 57 7 1 Checking Calibration 57 7 1 1 Checking the Master Current Source eeeeeesseees 57 TAZ Resistance Measure ment aso aec AETA 58 7 1 2 1 Zero Ohms CHECK aieo debe oet acie ra ro too Eres eka TRe dor ade 58 7 1 2 2 400 Q Internal Reference Resistor eeeeeeeee 59 7 1 2 3 100 Q Internal Reference Resistor 60 7 1 2 4 25 Q Internal Reference Resistor eeeeeee 60 7 1 2 5 10 Q Internal Reference Resistor eeennn 60 7 1 2 6 1 Q Internal Reference Resistor eeeeen 60 dal Voltage Measure melts oc cedet del edet doctus feo e Eth edd Men 61 Paleo Aero NV OWASe OSEE tcsanrasss E m DT 61 T0292 Volse Spat Che keruoneness dota doesnt ee psu 61 7 2 Xii Lo EE C 62 7 2 1 Calibrate Master Current Source eeeseseeeen 63 7 2 1 1 Calibrating the 400 Q Internal Reference Resistor 64 7 2 1 2 Calibrating the 100 Q Internal Reference Resistor 65 7 2 1 3 Calibrating the 25 Q Internal Reference Resistor 65 Page 3 of 90 Issue 1 01 8 1 82 7 2 1 4 Calibrating the 10 Q Internal Reference Resistor 65 7 2 1 5 Calibrating the 1 Q Internal Reference Resistor 66 VEA Calibrate Voltage Zeros ose etu E bk toco Mte eios 66 7 2 3 Calibrating Voltage Span ise e tree AA 67 RS232 INTER
45. eference junction compensation Connect the N type thermocouple to channel 1 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 1s 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 Page 18 of 90 Issue 1 01 Y Axis X Axis Channel Scale Minutes eje 1e 8 19 L Minimum Time Units 0 058 Seconds lind Minutes 0 038 ed oa 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 Em E ERE 046428575 Mean of last 100 3 80000e 2 4 00000e 2 4 20000e 2 4 40000e 2 4 60000e 2 4 80000e 2 5 00000e 2 5 20000e 2 5 40000e 2 5 60000e 2 5 80000e 2 950 1 000 1 050 1 100 aale m 1 200 Time j s Page 19 of 90 Issue 1 01 3 Driving Your microK 3 1 Introduction The operator interface for the microK is provided through the touch screen an
46. ense 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 1s 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 100Q reference resistor with a ImA sense current use SENS RAT RANG 130 1 This will set the microK to the middle range 8 2 6 16 Command SENSe RATio RANGe Format SENSe RATi0 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 Page 81 of 90 Issue 1 01 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 8 2 6 15 but has its sense current set to 10mA would respond to the command SENS RAT RANG with
47. entical There is after all no difference between these two measurements apart from the fact that they are Page 55 of 90 Issue 1 01 taken at slight different times The system noise will again determine the uncertainty of this unity ratio measurement 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 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 56 of 90 Issue 1 01 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
48. er details of how to connect a PC to your microK see section Once you have established communication with your microK type in the following commands and check that the measured current is within the given limits command current limits TEST CURR 0 1 0 0996 to 0 1004 mA TEST CURR 1 0 996 to 1 004 mA TEST CURR 10 9 96 to 10 04 mA TEST CURR 0 1 0 09966 to 0 1004 mA TEST CURR 1 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 correct 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 1 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 Page 58 of 90 Issue 1 01 V 4 Terminal Short Circuit Configure the microK to measure a Default PRT at 1mA against the internal 100Q reference on the 125Q range on channel 1 other chan
49. er reading will therefore be lt 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 nstrument tab see section 3 7 7 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 based on the last filename used 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 Page 26 of 90 Issue 1 01 section 3 11 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 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 To import the data into Micr
50. erefore 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 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 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 So GE GE S gt GE GE gt Information in the database is password protected to help you comply with the requirements 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 ass
51. fast reversal 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 1 f noise 6 2 Substitution Topology In conventional potentiometric instruments a common DC current is passed through a thermometer Rx and reference resistor Rs A voltmeter is switched between reading the voltage across Rx and Rs and the ratio of the two readings n 1s calculated Amplifier Conventional Potentiometric Resistance Measurement Page 52 of 90 Issue 1 01 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 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 is common to both the reference
52. gle tab check that the Mean agrees with the calibrated value of the resistance standard to within I3ppm half of the specification limit of the calibrated value and that the standard deviation S D 1s less than 0 000005 Page 60 of 90 Issue 1 01 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 channels 7 1 3 1 Zero Voltage Offsets Short out the 4 measurement terminals on all 3 channels using a piece of un insulated wire for each channel Configure the microK to measure a Default Thermocouple on the 0 125 V range with units of Volts Use 1 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 1s less than 0 000000250 0 25u V and that the standard deviation S D 1s less than 0 000000050 0 05p V 7 1 3 2 Voltage Span Check Connect a stable low noise voltage source wit
53. h a nominal value of 50mV to channel 1 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 61 of 90 Issue 1 01 Voltage V Source w Configure the microK to measure a Default Thermocouple on the 0 125V range with units of Volts Use 1 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 1n the Single tab check that the Mean value agrees with the applied voltage to within 0 000000250V 0 25u V and that the standard deviation S D is less than 0 000000050V 0 05u V 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 01 ppm We therefore recommend that you return your microK to Isothermal Technology or one of its appointed service centres annually for
54. h 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 Page 44 of 90 Issue 1 01 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 of thermistor connected to another measurement channel Thermocouple Measurement Reference Junction Junction PRT The microK supports thus 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 Page 45 of 90 Issue 1 01 THERMISTOR Because the resistance of thermistors used
55. han this will be ignored The offset is stored as a floating point number and will therefore be subject to some rounding less than 0 12ppm of value Example to subtract an offset of 0 123u V from voltages measured on channel 3 use CAL OFFS3 0 123 Page 85 of 90 Issue 1 01 8 2 6 20 Command CALibrate OFFSet Format CALibrate OFFSet lt channel gt Reports the offset subtracted from voltage measurements on channel 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 23E 07 8 2 6 30 Command CALibrate GAIN Format CALibrate GAIN gain polarity adjustment Adjusts the value of gain for polarity by the factor adjustment The parameter gain must be one of three strings defining the nominal gain of the microK pre amplifier l X2 X10 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 12ppm of value Example for a microK that has been found to have a voltage gain for positive readings on its x40 range that is low by a factor of 1 000123 see section 7 2 3 the gain can be corrected using CAL GAIN X40 POS 1 000123 8 2 6 31 Command CALibrate GAIN Format CALibrate GAIN lt gain gt lt polarity gt Reports the total calibration adjustment
56. hannel 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 1s The reading rate for three PRTs with one sample per reading will therefore be 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 nternal DiskOnChip solid state drive memory or an External USB flash Page 24 of 90 Issue 1 01 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 7 The internal memory used has a capacity of 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 based on the last filename used 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 11 for details on password protection The Shift key toggles the alpha keys between upper and lower case The indicator by the Start Save
57. he 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 Page 33 of 90 Issue 1 01 n WILKINS 25 o Resistor Resistor Name Value WILKINS 25 L 24 999875 d Manufacturer s Name n Serial Number W151256 m Calibration Due 30 10 2007 m 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 number of the selected reference resistor If you are creating a new reference resistor entry the ellipses button by the box becomes active
58. his button to open a Numeric Keypad window and enter the minimum operating temperature for the 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 Page 32 of 90 Issue 1 01 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 mw J m 01 e beooao cono _ keo xoono P _ soc ono _ wss 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 thermometer or the current entry for a new thermometer from the database OK button Press this button to confirm the changes and close the Window 3 2 Edit Resistors Press t
59. ing 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 1s suggested Verify that the supply cordset is undamaged and that the enclosure is bonded to protective earth Do not apply earth test currents to any front panel terminal nor to the shrouds of the USB RS232 or GPIB connectors Page 8 of 90 Issue 1 01 The product is designed to comply with EN 61010 1 and can be flash tested It 1s 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
60. m Current Cable Length Internal Standard Resistors Input Connectors Interfaces Display Operating Conditions Power Size Weight Notes 0 10mA 0 4 of value 7uA resolution 2 8uA lt 30m maximum 10Q per core or 10nF shunt capacitance 10 0 1 TCR 10ppm C typical stability x25ppm year 100 0 1 TCR 0 6ppm C typical stability 5ppm year 25 100 400 Q 0 1 TCR 0 3ppm C typical stability 5ppm year Cable Pod connectors for 4mm plugs spades or bare wires Contact material gold plated tellurium copper RS232 9 600 baud USB 1 1 host 163mm 6 4 VGA 640 x 480 colour TFT LCD 15 30 C 50 85 F 10 90 RH for full specification 0 40 C 32 105 F 0 99 RH operational 88 264V RMS 47 63Hz Universal 20W maximum 1 5A RMS maximum 520mm x 166mm x 300mm 20 5 x 6 6 x 11 9 W x D x H 12 4kg 271b 1 The 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 Page 89 of 90 Issue 1 01 10 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 10 1 CE Declaration European Community Electromagnetic Comp
61. n the Settings tab select the channel to which the reference 1s 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 1s 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 15 of 90 Issue 1 01 Y Axis X Axis Channel Scale Minutes eg 1o eeel Minimum Time Units 47 77 m Seconds Maximum 8 Minutes wx I e m 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 E Channel peu SS ee Mean of last 100 Du CN 47 77900 47 77800 47 77700 47 77600 47 77500 47 77400 47 77300 47 77200 47 77100 47 7 7000 1 800 1 850 1 900 1 950 2 000 2 050 Time s 2 2 Measuring Temperature with a Thermocouple From startup press Resume to restart your microK Page 16 of 90 Issue 1 01 Isothermal Technology microK v1 2 3 S N O6
62. n the next resistance measurement will respond to the command SENS FRES REF with 2 8 2 6 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 5 V 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 Page 79 of 90 Issue 1 01 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 the resistance of the device under test Example to set the microK to measure a PRT that has a maximum resistance of 130Q using a 100Q reference resistor with a ImA sense current use SENS FRES RANG 130 1 This will set the microK to the middle range 8 2 6 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
63. nce 79 8 2 6 11 Command SENSe FRESistance RANGe se 79 8 2 6 12 Command SENSe FRESistance RANGe eee 80 8 2 6 13 Command SENSe RATio REPFerence se 80 8 2 6 14 Command SENSe RATi0 REFerence ees 81 8 2 6 15 Command SENSe RATI0 RANGE erm 81 8 2 6 16 Command SENSe RATIo RANGe eee 81 8 2 6 17 Command UNI Mate iot doro petto fate ate eoa ovt oibus 82 8 2 6 18 Command FETEI cce erts ue od niece ia dr ceo ee Ens 82 8 2 6 19 Command EAD etii Ces 82 8 2 6 20 Command MEASure VOLTage essere 83 8 2 6 2 1 Command MEASure FRES REF eere 83 6 2 6 22 Command MEASure RAT REF eene 83 8 2 6 23 Command C URReHt eere teesamcseteaptertnctedsictsacees 84 6 2 6 24 Command TEST CURRent eee 84 8 2 6 25 Command CALibrate CURREent een 84 8 2 6 26 Command CALibrate REFerence eene 85 8 2 6 27 Command CALibrate REFerence eere 85 8 2 6 28 Command CALibrate OFFSet eene 85 8 2 6 29 Command CALAibrate OFFSet eene 86 8 2 6 30 Command CALibrate GAIN eee 86 8 2 6 3 1 Command CALibrate GAIN 0 0 eee mne 86 8 2 6 32 Command CALibrate PASSWotd eene 87
64. nd and the channel number as this command makes use of the numeric suffices feature of SCPI described in section 8 2 2 This command 1s equivalent to SENS FUNC volt SENS CHAN channel SENS VOLT RANG voltage range and READ The voltage range specified 1s 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 8 2 6 21 Command MEASure FRES REF Format MEASure SCALar FRESistance lt channel gt REFerence lt reference gt resistance range current Initiates and reports a resistance measurement on lt channel gt against a reference on channel lt 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 8 2 2 This command is equivalent to SENS FUNC fres SENS FRES REF lt reference gt SENS FRES RANG resistance range current SENS CHAN channel and READ Example to set the microK to measure a PRT on channel 1 that has a maximum resistance of 130 using a 100 reference resistor on channel 2 with a ImA sense current use MEAS FRESI REF2 130 1 8 2 6 22 Command MEASure RAT REF Format MEASure SCALar RATio lt channel gt REFerence lt reference gt lt resistance range gt lt current gt Page 83 of 90 Issue 1 01 Initiates and report
65. nels 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 1 e 0 08ppm of the 125 range and that the standard deviation S D is less than 0 00005 7 1 2 2 400 O Internal Reference Resistor Connect a stable external resistance standard with a nominal value of 100Q to channel 1 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 1mA against the internal 400 reference on the 500 range on channel other channels disabled Set the units to Ohms and use 1 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 Page 59 of 90 Issue 1 01 7 1 2 3 100 O Internal Reference Resistor Repeat the procedure for checking the 400 internal reference see section 7 1
66. ngs 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 1s less that 0 000000100 Calculate the value of the internal resistor from exernal reference 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 Page 64 of 90 Issue 1 01 7 2 1 2 Calibrating the 100 Q Internal Reference Resistor Repeat the procedure for calibrating the 400 internal reference see section 7 2 1 1 but configure the microK to measure a Default PRT at ImA against the internal 100Q reference on the 125Q range with channel 1 The command to adjust the value assigned to the 100Q internal reference is CAL REF204 R100 Where R 00 is the value calculated for the 100 2 internal reference 7 2 1 3 Calibrating the 25 Q Internal Reference Resistor Repeat the procedure for calibrating the 400 internal reference see section 7 2 1 1 but configure the microK to measure a Default PRT at ImA against the internal 25Q reference on the 125Q range with channel 1 The command to adjust the value assigned to the 25Q internal reference 1s CAL R
67. nufacturer 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 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 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 t
68. numeric form Settings allows you to configure the channels 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 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 Page 22 of 90 Issue 1 01 Single Multi Settings Instrument Channel pau a Mean of last 100 47 77900 47 77800 47 77700 47 77600 47 77500 47 77400 47 77300 47 77200 47 77100 47 77000 1 800 1 850 1 900 1 950 2 000 2 050 Channel box Use the up down buttons by the Channel box to select the channel you wish to view You can only view channels that are enabled so if a channel is disabled in the Settings tab 1t will not appear in the sequence and will not be measured This means that the up down buttons have no effect if only one channel is enabled The numeric display shows the last reading together with the mean and standard deviation of the most recent of readings the number or 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
69. ny measurement you will have to enter information about the thermometer into the microK s database When the main window opens press the nstrument tab Single Multi Channel Hmn Clear Graph cess O RESIS Se E m O e nm og A Ol c wo wi O oo 0 0 Time s In the Instrument tab press Edit Thermometers Single Multi Settings Instrument System Calibration o9 c Edit Thermometers Edit Resistors Set Date and Time Calibration Backup Data Update Software Clear Data Files Backup Configuration Change Password Load 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 3 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 90 Issue 1 01 e SPRT 1 o Thermometer Thermometer Name Thermometer Type Ew ee le Manufacturer s Name Min Temperature Isothermal Tecchnology m DOES m Serial Number Max Temperature som so Calibration Due Conversion 15 12 2007 m m o Press Coefficients to open the coefficients window Press the ellipses buttons to enter the calibration data for the thermometer from its calibration
70. o 100uQ resistance uncertainty With a I mA sense current this corresponds to a voltage uncertainty of 0 1u V The microK has been optimised for electromagnetic compatibility minimising emissions and maximising immunity However since the microK is capable to measuring to such low signal levels it is worthwhile adopting good electrical measurement practices Here are a few guidelines The most sensitive points are the inputs to the microK measuring to better than O 1u V 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 T respectively it is better to use a screened cable and to connect the screen to the measurement ground terminal above the input terminals Screen Measurement Ground Terminal 1 1X SPRT or BEEN E LL 7 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 c
71. ociated with it will be Page 39 of 90 Issue 1 01 loaded and used by the measurement system This means that you do not need to enter information 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 1s 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 using the Reference Resistor box in the Settings tab see section 3 6 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 G5 G5 SD Information in the database is password protected to help you comply with the requirements 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 9 This 1s useful if
72. or Fuse USB B On Off Connector GPIB Switch unused Connector RS232 unused Connector Page 11 of 90 Issue 1 01 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 Windows applications it 1s 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 Further tutorials will be added to the website we have set up for microK users see www microk co uk You may wish to share your experience of using your microK by adding your own tutorial to the website 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 1 2 3 S N O6 PPOO7 firmware version 2 00 Resume Measurement system initialised Page 12 of 90 Issue 1 01 Before making a
73. osoft Excel M simply click open within Excel select AII Files under File Types browse to the required file on the USB flash drive and then click Finish in the Text Import Wizard that appears 3 6 The Settings Tab Select this tab to configure each channel for the required measurements Single Multi Settings Instrument Channel Units PES ope eem 1 Thermometer Current mA Cx pecie G Eme Conversion Samples per Reading tee 12 fede Range Ohms Readings in Rolling Statistics Bo B Lo jn s J Reference Channel Reference Resistor Interna 100R o i 1100 0000 L Channel box Use the up down buttons to select the channel you wish to configure 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 buttons 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 Page 27 of 90 Issue 1 01 thermometers to the microK s Thermometer Database see section 3 7 1 these will also appear in the list within this box Conversion box If the selected thermometer is one of the default types you can
74. ox 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 0 imA 2mA Custom 0 5mA 5mA x je SIBES OQ ZN imA iO0mA 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 Buttons for V2 and xvV2 are included to make extrapolation to zero power easier since changing the voltage on 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 1s most Page 29 of 90 Issue 1 01 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 N2 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 1s 0 4
75. r 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 EMEs from the metal silicon junctions in solid state switching devices are potentially higher than for mechanical relays under the same temperature eradient 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 result 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 1s 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 id
76. red 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 10 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 nternal DiskOnChip solid state drive memory or an External USB 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 Page 38 of 90 Issue 1 01 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 th
77. 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 Page 53 of 90 Issue 1 01 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
78. rmal Technology microK 400 261067 1 firmware version 1 20 8 2 6 2 Command RST Format RST Performs a reset equivalent to a power on reset of the measurement system firmware 8 2 6 5 Command SENSe FUNCtion Format SENSe FUNCtion function Selects the measurement function The parameter function must be one of the following valid SCPI parameters VOLTage DC l FRESistance i RATio Example to set the microK to measure ratio use SENS FUNC RAT 8 2 6 4 Command SENSe FUNCtion Format SENSe FUNCtion Reports the current measurement function Page 777 of 90 Issue 1 01 Example a microK set to measure voltage will respond to SENS FUNC with VOLTAGE 8 2 6 5 Command SENSe CHA Nnel Format SENSe 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 8 2 6 6 Command SENSe CHANnel Format SENSe CHANnel Reports the channel selected for the next measurement Example a microK set to measure channel 1 on the next measurement will respond to SENS CHAN with 1 8 2 6 7 Command 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 0 0 12
79. s a resistance ratio measurement on lt channel gt against a reference on channel lt 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 8 2 2 This command is equivalent SENS FUNC rat SENS RAT REF reference SENS RAT RANG resistance range current SENS CHAN channel and READ Example to set the microK to measure the resistance ratio of a PRT on channel 1 that has a maximum resistance of 130 against a 100 2 reference resistor on channel 2 with a 1mA sense current use MEAS RATI REF2 130 1 8 2 6 23 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 8 2 6 24 Command TEST CURRent Format TEST CURRent current Immediately sets the sense current on channel 1 to current Example to set the sense current on channel 1 to 5mA use TEST CURR 5 8 2 6 25 Command CALibrate CURRent Format CALibrate CURRent actual current This command is used after using the TEST CURR 1 command and measuring the current from channel 1 see section 7 2 1 It uses
80. s using a piece of un insulated wire for each channel 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 66 of 90 Issue 1 01 shown as 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 05u V Now adjust the zero offsets using the commands CAL OFFS1 offset CAL OFFS2 offset2 CAL OFFS3 offsets 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 3 Calibrating Voltage Span Connect a stable low noise voltage source with a nominal value of 50mV to channel 1 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 Source w Configure the microK to measure a Default Thermocouple on the 0 125V range with
81. 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 Page 43 of 90 Issue 1 01 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 capability of the microK 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 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 eac
82. sistance ratio ohms volts or temperature units C F or K Algorithms for conversion to temperature include PRTs ITS 90 Callendar Van Dusen IEC751 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 at this time so suggest you read the safety section below take one of the tutorials in section 2 Page 6 of 90 Issue 1 01 and then refer back to the manual using the list of contents to find additional information as required 1 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 e
83. so the uncertainty associated with this extrapolation back to zero power is only 0 8 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 ellipses button to open a Numeric Keypad window and enter the required number directly The number of samples may be between 1 and 100 inclusive 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 referen
84. sword dC 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 6 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 Page 36 of 90 Issue 1 01 Year 2006 m Date Format dd mm yyyy Month m O mm dd yyyy oy fd or B 1 Minute m Second m Press the ellipses buttons by each box to open 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 7 Backup 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
85. t is happening in the frequency domain The over sampling used in A converters means that the quantisation noise caused by the 1 bit ADC is spread over a wide bandwidth whereas the signal we are looking for 1s 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 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 would 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 nuoc input HE ej m roci pe ala 5 bit igre ea 5 bit Mud data Digital output Filter Decimator Multi Bit Z A ADC The
86. the actual current entered to adjust the master current source the correct current Page 84 of 90 Issue 1 01 Example the current from channel 1 after using the command TEST CURR 1 was measured as 1 00123 To adjust the master current source correctly use CAL CURR 1 00123 8 2 6 26 Command CALibrate REFerence Format CALibrate REFerence lt reference gt actual resistance Used to calibrate the internal reference standard by assigning a new actual resistance to it The channel numbers numeric suffices used for the internal resistor are given in section 8 2 2 The calibrated value is stored as a floating point number and will therefore be subject to some rounding less than 0 12ppm of value Example if the value of the internal 100 reference has been measured as 100 00123 the new value can be assigned to it using CAL REF204 100 00123 8 2 6 27 Command CALibrate REFerence Format CALibrate REFerence lt reference gt 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 25Q reference having a calibrated value of 25 01234 will respond to CAL REF203 with 25 01234 8 2 6 28 Command CALibrate OFFSet Format CALibrate OFFSet lt channel gt offset Adjusts the voltage offset for channel used when making voltage measurements The offset range is 2uV attempts to apply an offset greater t
87. 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 Update Software Press the Update Software button to update the software on your microK The new application microk exe should be located in the root directory of a USB flash drive connected to the front panel USB connector 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 version on the flash drive you will be advised of the version levels and offered the opportunity to update to the later version You will be prompted to enter the password before proceeding If the Page 35 of 90 Issue 1 01 flash drive does not contain a more recent version the software will simply restart 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 5 Change Password Press the Change Password button to change the security password see section 3 11 for details of password protected settings A window will then open to allow you to change the password confirm NewPas
88. 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 Page 23 of 90 Issue 1 01 Y Axis X Axis Channel Scale Seconds eg 1o ee ejl Minimum Time Units b B Seconds Maximum O Minutes fo o e 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 1 second and 1000 minutes 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 The numeric and graphical outputs are updated as new readings are made The time between readings depends on the settings for that c
89. 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 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 to eliminate the thermal EMFs The limitation 1s then the thermal EMFs generated by the devices used to implement this reversal Page 54 of 90 Issue 1 01 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 numbe
90. units of Volts Use 1 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 1s less than 0 000000050V 0 05u V Calculate the require gain from Page 67 of 90 Issue 1 01 actual value gain measured value Now apply the new gain by typing the command CAL GAIN X40 POS gain The value entered can be read back using CAL GAIN X40 POS Repeat the procedure with the voltage source set to 50mV 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 68 of 90 Issue 1 01 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 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 1 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 rea
91. xtreme environments refer to specification in Section 9 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 terminals 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 Page 7 of 90 Issue 1 01 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 1 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 temperature range of 5 C to 40 C with maximum relative humidity of

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