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Issue: 1.04

10.3 Making Measurements using SCPI Commands

The microK’s measurement system is controlled by a microprocessor connected

to the rear panel RS232 interface and a GPIB port. The measurement system can

be controlled by SCPI commands from either of these. The firmware makes no

distinction between commands received on the RS232 interface and those from

the GPIB and will process these in the order in which they are detected. If a

response is expected, it will always be sent on the interface (RS232 or GPIB) on

which the corresponding command was sent.

There is no direct interference between measurements made using the front panel

operator interface and measurements requested using SCPI commands. However,

measurements take some time to complete so there may be a delay in responses

to SCPI commands if measurements are being made via the front panel operator

interface. To avoid unnecessary delays to responses to SCPI commands, you can

stop all measurements requested via the front panel operator interface. The

easiest way to do this is to restart the microK and then not press

Resume

in the

opening window. The main application that provides the user interface will then

not start and no measurements will be requested.

10.3.1

Measuring Resistance using SCPI Commands

In order to measure the resistance of a PRT, you need to:

set the microK to measure resistance

set the sense current

select the measurement range

select the measurement channel

select the reference channel

make the measurement

If you want to measure a 25.5

Ω

SPRT up to a maximum resistance of 30

Ω

against the internal 100

Ω

reference, the maximum resistance that the

measurement system sees is 100

Ω

. 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

Содержание micro-800

Страница 1: ...ual Applies to Software version 1 4 16 Firmware version 3 17 Isothermal Technology Limited Pine Grove Southport Merseyside PR9 9AG T 44 0 1704 543830 F 44 0 1701 544799 E info microk co uk W www micro...

Страница 2: ...21 3 4 The Single Tab 22 3 5 The Multi Tab 25 3 6 The Settings Tab 26 3 7 The Instrument Tab 31 3 7 1 Edit Thermometers 31 3 7 2 Edit Resistors 34 3 7 3 Calibration 35 3 7 4 Restart Software 35 3 7 5...

Страница 3: ...3 Minimising Thermal EMFs 55 6 4 Solid State Switching 56 6 5 Inherent Stability 56 6 6 Eliminating Self Heating Effects 57 7 CALIBRATION 58 7 1 Checking Calibration 58 7 1 1 Checking the Master Curr...

Страница 4: ...ng SCPI Commands 79 10 3 1 Measuring Resistance using SCPI Commands 79 10 3 2 Measuring Voltage using SCPI Commands 80 10 4 SCPI Commands 81 10 4 1 Command IDN 82 10 4 2 Command RST 82 10 4 3 Command...

Страница 5: ...4 27 Command CALibrate REFerence 90 10 4 28 Command CALibrate REFerence 90 10 4 29 Command CALibrate OFFSet 91 10 4 30 Command CALibrate OFFSet 91 10 4 31 Command CALibrate GAIN 91 10 4 32 Command CAL...

Страница 6: ...se 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...

Страница 7: ...re safe to use in laboratory or light industrial environments It is not intended for use outdoors or in extreme environments refer to specification in Section 11 The microK is likely to be connected t...

Страница 8: ...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 humid...

Страница 9: ...trical outlet The power switch is located at the rear of the instrument immediately below the IEC connector When you turn your microK on it will go through a standard Windows CE boot sequence and then...

Страница 10: ...old cathode fluorescent lamp backlight A touch panel is mounted in front of the display so that you can control the instrument by simply touching the buttons displayed on the LCD The touch panel is an...

Страница 11: ...onnector power switch fuse module plus the interface connectors that allow you to connect your instrument to a PC The RS232 and GPIB ports allow you to control the instrument and take measurements fro...

Страница 12: ...w 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 desc...

Страница 13: ...press Edit Thermometers 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 secu...

Страница 14: ...ndow 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 us...

Страница 15: ...ings tab select the channel to which the reference is connected in the Reference Channel box and the reference resistor entry in the Reference Resistor box Press the Single tab to see the measurements...

Страница 16: ...o 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 2 2 Measuring Temperature with a Thermocouple Fr...

Страница 17: ...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 In the Settings tab disable channels 2 and 3 thi...

Страница 18: ...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 Th...

Страница 19: ...Page 19 of 97 Issue 1 04 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...

Страница 20: ...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 sys...

Страница 21: ...e 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 val...

Страница 22: ...rm 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 measuremen...

Страница 23: ...asured 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...

Страница 24: ...ad 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...

Страница 25: ...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 ke...

Страница 26: ...e Instrument tab see section 3 7 9 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...

Страница 27: ...ether 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 Y...

Страница 28: ...utton in this window allows you to select one of the microK s three external channels or any expansion channel provided by a microsKanner Reference Resistor box PRTs and thermistors only If an interna...

Страница 29: ...ce 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 box PRTs and thermistors only Pr...

Страница 30: ...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 t...

Страница 31: ...date and passwords backup load instrument configurations or update the software 3 7 1 Edit Thermometers Press Edit Thermometers to create edit or delete a thermometer in the database You will be promp...

Страница 32: ...try 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...

Страница 33: ...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 fo...

Страница 34: ...ference 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...

Страница 35: ...nd 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 De...

Страница 36: ...the opportunity to update to the later version you will also be prompted to enter the password before proceeding If the flash drive does not contain a more recent version the software will simply rest...

Страница 37: ...e 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 7 Port Settings Press Port Settings to...

Страница 38: ...nsfer 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 facilit...

Страница 39: ...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 flas...

Страница 40: ...ates 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 wa...

Страница 41: ...the out of calibration issue is resolved Enter data on the reference resistors you use with your resistance thermometers into the microK s database see section 3 7 2 You can then use one of these ref...

Страница 42: ...ing procedures that meet the requirements of accreditation bodies and should alleviate some of the concerns that accreditation bodies have about the integrity of measurements You need to enter the pas...

Страница 43: ...clamping surface does not rotate as it clamps the wire in order to avoid damaging it The Cable Pod mechanism is made from a high strength polymer but nonetheless may be subject to mechanical damage i...

Страница 44: ...n connected to the single end of the 3 wire PRT as follows V I 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 resi...

Страница 45: ...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 gua...

Страница 46: ...Reference Junction Junction Measurement Thermocouple V I PRT The microK supports this arrangement by allowing you to use a temperature measured by another input channel as the reference junction temp...

Страница 47: ...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...

Страница 48: ...ts 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...

Страница 49: ...ur wire connection to the PRT or reference resistor using the voltage sense and current terminals marked V and I respectively it is better to use a screened cable and to connect the screen to the meas...

Страница 50: ...trical 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...

Страница 51: ...echnique but uses multi bit feedback to achieve performance that is not achievable with conventional ADCs In a conventional ADC the analog input signal is subtracted from the output of a 1 bit DAC bef...

Страница 52: ...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 frequen...

Страница 53: ...00 so that the performance of the microK is not limited by the ADC technique but by the electronic devices used in the ADC and the rest of the measurement system Another benefit of the new ADC is its...

Страница 54: ...he 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...

Страница 55: ...tance thermometers by reversing the current and averaging the measurements the offsets in the two measurements cancel each other out when the readings are averaged together However this technique cann...

Страница 56: ...erature gradient However the very small size of the die within the semiconductor devices means that there would be little opportunity for thermal gradients giving them a strong advantage over their me...

Страница 57: ...gned 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 measur...

Страница 58: ...l 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 contr...

Страница 59: ...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 u...

Страница 60: ...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 tempe...

Страница 61: ...t 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 10 reference on the 25 range on channel 1 7 1...

Страница 62: ...3 channels using a piece of un insulated copper wire use pure copper wire to avoid generating unwanted thermal EMFs for each channel V I Configure the microK to measure a Default Thermocouple on the...

Страница 63: ...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...

Страница 64: ...OT necessarily the same as the password used in the touch screen operator interface The password is initially set to 1234 but should be changed for security reasons see section 10 4 33 You can now use...

Страница 65: ...ecent 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 wit...

Страница 66: ...e 25 internal reference is CAL REF203 R25 Where R25 is the value calculated for the 25 internal reference 7 2 5 Calibrating the 10 Internal Reference Resistor Connect a stable external resistance stan...

Страница 67: ...wire use pure copper wire to avoid generating unwanted thermal EMFs for each channel V I Type in the following commands to remove the zero offset correction for all three channels CAL OFFS1 0 CAL OFF...

Страница 68: ...tellurium copper that has a high copper content and low thermal EMF to pure copper Brass connectors must NOT be used V I Voltage Source Configure the microK to measure a Default Thermocouple on the 0...

Страница 69: ...ed 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 entere...

Страница 70: ...ection 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 f...

Страница 71: ...usually located in the Accessories Communications folder If you have installed a minimum laptop or custom configuration without this component for your Windows operating system you may need to install...

Страница 72: ...e command by pressing the carriage return or Enter keys the microK should then respond with a string in the form Isothermal Technology microK 400 10 P190 firmware version 3 17 This confirms that you h...

Страница 73: ...th IFC 10 SRQ Service Request 22 GND Ground paired with SRQ 11 ATN Attention 23 GND Ground paired with ATN 12 GND Shield 24 GND Logic Ground Shell Frame Ground cable screen Unlike the RS232 interface...

Страница 74: ...g Port Settings in the Instrument tab see section 3 7 7 9 2 Establishing a GPIB Connection Connect your microK to a GPIB Controller using a standard straight through GPIB cable Send IDN to the GPIB ad...

Страница 75: ...ponses from the microK on the RS232 interface are always terminated by a Carriage Return character If commands are sent to the microK s GPIB port they can be terminated by a Line Feed character ASCII...

Страница 76: ...he first four letters or 3 if 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...

Страница 77: ...o measure the voltage on channel 3 the command used would be MEAS VOLT3 10 2 2 Parameters If a command requires parameter s these follow the command and are separated from it by a space If more than o...

Страница 78: ...Page 78 of 97 Issue 1 04 CURRENT 1000UA CURRENT 1 The following prefixes are available prefix name factor N or n nano 10 9 U or u micro 10 6 M or m milli 10 3 K or k kilo 10 3 MA or ma mega 10 6...

Страница 79: ...I commands if measurements are being made via the front panel operator interface To avoid unnecessary delays to responses to SCPI commands you can stop all measurements requested via the front panel o...

Страница 80: ...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...

Страница 81: ...UPPer resistance range current RANGe UPPer INITiate IMMediate ALL FETCh SCALar READ SCALar READ channel MEASure SCALar VOLTage DC channel voltage range FRESistance channel REFerence reference resistan...

Страница 82: ...Isothermal Technology microK 400 261067 1 firmware version 1 20 10 4 2 Command RST Format RST Performs a reset equivalent to a power on reset of the measurement system firmware 10 4 3 Command SENSe FU...

Страница 83: ...oK set to measure channel 1 on the next measurement will respond to SENS CHAN with 1 10 4 7 Command SENSe VOLTage RANGe Format SENSe DC VOLTage RANGe UPPER voltage range Sets the range for the next vo...

Страница 84: ...for the next resistance measurement use SENS FRES REF 204 10 4 10 Command SENSe FRESistance REFerence Format SENSe FRESistance REFerence Reports the channel selected as the reference channel for the n...

Страница 85: ...ing the CURRent command The current used to calculate the range may be different from that specified when the range was set using the SENSe FRESistance RANGe command The reported range is the actual r...

Страница 86: ...th 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 refe...

Страница 87: ...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 th...

Страница 88: ...Ratio R Ohms V Volts K Kelvin C Celsius F Fahrenheit If the requested channel does not exist or is not enabled the microK will respond with not enabled X 10 4 21 Command MEASure VOLTage Format MEASure...

Страница 89: ...ce reference resistance range current Initiates and reports a resistance ratio measurement on channel against a reference on channel reference using resistance range with sense current note that there...

Страница 90: ...e 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 10 4 27 Command CALibrate REFerence Format C...

Страница 91: ...refore be subject to some rounding less than 0 12ppm of value Example to subtract an offset of 0 123 V from voltages measured on channel 3 use CAL OFFS3 0 123 10 4 30 Command CALibrate OFFSet Format C...

Страница 92: ...meter 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...

Страница 93: ...by re powering the microK or using CAL LOCK see section 10 4 35 Example to unlock enable the calibration adjustment on a microK with the default password 1234 use CAL UNL 1234 10 4 35 Command CALibrat...

Страница 94: ...oltage uncertainty 250nV between 0 and 20mV equivalent to 0 01 C for Gold Platinum thermocouple at 1000 C Resolution Resistance 0 01ppm of range Voltage 2nV 125mV range Stability Resistance excluding...

Страница 95: ...tellurium copper Interfaces RS232 9 600 baud GPIB USB 1 1 host Display 163mm 6 4 VGA 640 x 480 colour TFT LCD Operating Conditions 15 30 C 50 85 F 10 90 RH for full specification 0 40 C 32 105 F 0 99...

Страница 96: ...12 2FCC Statement This equipment has been tested and found to comply with the limits for a Class A digital device pursuant to part 15 of the FCC Rules These limits are designed to provide reasonable...

Страница 97: ...onducted Emissions EN61326 1997 CFR47 2005 Radiated Emissions EN61326 1997 CFR47 2005 Conducted Immunity EN61326 1997 Radiated Immunity EN61326 1997 Electrical Fast Transients EN61326 1997 Electrostat...

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