UNIVERSAL CALIBRATOR M

Transcription

1 INTRODUCTION UNIVERSAL CALIBRATOR M Before going through the instruction manual for actual use of the instrument go through the specifications and take note of the following points carefully 1. No external voltage source should be imposed on the instruments voltage source output terminals. The voltage output is short circuit proof. 2. No current source should be forced through the current output terminals. An open circuit voltage of 27 volts exists on the current terminals. This voltage may be less with full 60mA load and in case when battery low indication is there in battery mode of operation. With mains voltage operation or with fully charged battery compliance voltage of current source will be 24 volts. The current source is open circuit protected. 3. For measurement of external voltage/current sources use the "sense" terminals only after selecting proper mode and range. The measurement circuit ( sense terminals ) is protected upto 30V only in any of the ranges. Applying any voltage above that may damage certain components within the instrument. 4. At the time of switch 'ON' of the instrument in Mains or Battery, display will first show the range selected for about 3 seconds. This time is required for internal reference reading and software initialization. After this the actual reading will be displayed. If the range selection is not proper instrument will display a message 'error' and stay in that mode only until a valid range is selected. 5. The instrument goes through an auto calibration cycle every 3 minutes. At which time the instrument reading will freeze to last reading for about 2 seconds. The same auto calibration cycle is executed when a new range is selected. This auto calibration cycle corrects for drifts in the instrument because of self heating. After changing range allow minimum 3 minutes time in the selected function for the instrument to stabilize at its rated accuracy. 6. Though every care has been taken to protect the instrument against voltage spikes, transients etc., should the instrument stop functioning, switch off the instrument and switch it on once again. The instrument is capable of operating on mains as well as battery operation depending upon mains supply presence. If mains supply fails instrument tries to start functioning in battery mode where the instrument may not be able to start properly. This happens because of series resistance of batteries and slow dropping of the mains supply. In such an event switch off and switch on once again to start with proper functioning. Operation Manual 1 of 19

2 7. While measuring RTD care is to be taken that proper mode is selected. If ma mode is wrongly selected with 60 ma range, the current of 60 ma can flow through the RTD, leading to its damage. It is always safer to select proper mode and type of RTD and then connect RTD. In case of no connection for RTD the instrument may read under or over range. After connecting RTD the reading will come, but it will be better to wait for 3 minutes for a stable accurate reading. ( This is because of open circuit voltage of the current source in the instrument. ) 8. If the 'NULL' switch is used in a particular range, make sure to release it before you change to new range. Keeping 'NULL' switch pressed may lead to wrong reading in other ranges. 9. The following ANSI symbols are used for various standard thermocouple types E Chromel - Constantan J Iron - Constantan K Chromel Alumel T Copper Constantan B Pt 30% Rh - Pt 6% Rh R Pt 13% Rh - Pt S Pt 10% Rh - Pt GENERAL DESCRIPTION MASIBUS' UNICAL 3001M is a micro-controller based instrument, capable of measuring and calibrating process signals (instrumentation), with the most stringent accuracy demanded by the industry. At the heart of the instrument is an 8 bit micro-controller, an 18-bit serial analog to digital convertor and indigenously developed dedicated software, that makes this unique calibrator highly reliable, versatile and precise. SALIENT FEATURES Capable of measuring the output of or simulating thermocouple types, B, E, J, K, R, S, T (ANSI standard). Capable of measuring output of Pt-100 and Cu-53 RTD and 2K resistance. Simulation of resistance and RTD by simulator module. Software controlled AUTO CALIBRATION and AUTO ZERO LOOP within measurement cycle ensures zero short term and negligible long term drifts. Automatic cold junction compensation by means of simulated electronic ice point reference and 100% digital linearization eliminates use of conversion tables and thermometers. High accuracy of linearization achieved by 10th order polynomials for multiple segments. Cold junction temperature adjustment provided on front for proper tracking. Simulation of temperature in C or F Operation Manual 2 of 19

3 Digital calibration, no trimpots used. Measures simulates mv, V and ma. Independent settings for zero and span, switch selectable. This is useful for calibration of systems which read zero for some offset voltage or current, e.g., 4 ma corresponding to ZERO and 20 ma for SPAN. All values adjusted by means of 10 turn coarse and fine potentiometers. Digital nulling facility for offset cancellation and differential measurement. Mains-Cum-rechargeable battery operated with built-in charger. Six standard 'C' size cells are used for forming a 7.2V battery. Facility to display ambient temperature at any time during measurement just by a key press. Optional facility to measure/simulate two unique user defined mv v/s parameter characteristic. For 20 ma simulation, full 24 volts compliance voltage provided even in battery mode operation. SPECIFICATIONS Power Supply : 230/110V ± 10%, 50 Hz/60 Hz, or Builtin rechargeable battery Battery : Rechargeable 7.2V, 2.2AH power pack Battery Operation : Approximately 5 Hours in measurement mode and 4 Hours with 20 ma output. Battery charging time : 14 Hours for full charge Dimension : 240(W) X 135(H) X 185(D) mm. Cold Junction Compensation : Automatic from 0 C to 50 C in both measurement and simulation. CJC switch off with 0 C reference provided. Display : 5 Digit 0.56" RED high efficiency LED Discrete Leds to indicate selected function, Battery low indication and battery charging status Reading time : 2.5 readings/sec. Input impedance : More than 10 Mohm(mV, V, T/C) 10 ohm in ma Operating temperature : 0 to 55 C Operation Manual 3 of 19

4 Humidity range : 0 to 80% R.H. non-condensing Temperature Coefficient : % rdg/ C Protection : Voltage source Short circuit Current source Open circuit Power consumption : 10 VA Enclosure : General Purpose Functions : Function Range Resolution Accuracy Ambient 0 to 50 C 0.1 C ± 0.2 C 20 mv -5mV to +25mV 1 µv ± 0.03 % F.S. 200 mv -50mV to +250mV 10 µv ± 0.03 % F.S. 2 V -0.5V to +2.5V 0.1 mv ± 0.03 % F.S. 10 V -2.5V to +10V 1 mv ± 0.03 % F.S. 20 ma 0 to +25mA 1 µa ± 0.03 % F.S. 60 ma 0 to +60mA 10 µa ± 0.03 % F.S. B type T/C 450 C to 1750 C 0.1 C ± 2.0 C E type T/C -100 C to 1000 C 0.1 C ± 0.5 C J type T/C 0 C to 760 C 0.1 C ± 0.5 C K type T/C 0 C to 1370 C 0.1 C ± 0.5 C R type T/C 200 C to 1750 C 0.1 C ± 1.0 C S type T/C 0 C to 1750 C 0.1 C ± 1.0 C T type T/C -160 C to 400 C 0.1 C ± 0.5 C PT- 100 RTD -200 C to 850 C 0.1 C ± 0.5 C CU C to 200 C 0.1 C ± 0.5 C 2K ohm 0 to 2Kohm 0.1 ohm ± 0.03 % F.S. Notes: (1) For all ranges, ± 1 count digital inaccuracy will be applicable. (2) For mv, V and thermocouple ranges, source loading capability will be maximum 10mA. (3) For current ranges compliance voltage will be 24V in mains mode. With battery it may get reduced if battery is not fully charged. (4) For Pt-100, Cu-53 and 2K ohm ranges injection current of 0.5mA is used. 1. POWER SUPPLY OPERATION Operation Manual 4 of 19

5 The instrument is having facility for both mains and battery mode of operation. Generally it is shipped with battery in discharged condition for safety purpose. The battery starts getting charged automatically when mains supply is applied even if front switch is in OFF position. When battery is getting charged, front panel LED of 'BAT CHG' will be ON. For applying mains power, a standard 3-pin mains inlet is provided on back side. The power supply of the unit is either 230V AC or 110V AC set from factory. Refer test report for power supply rating. The supply is protected by a 500 ma fuse provided in the socket itself. One spare fuse is also provided in the socket. For operating the unit just press PWR switch with mains applied or battery fully charged. If battery is not charged, unit will not turn on and if the battery is partially charged, unit will turn on with a 'BAT LO' indication on front. Select desired range of operation. It will display selected range, and then the value being measured or simulated. WARNING : Don't operate the instrument for longer time after BAT LO warning LED is ON. The time for battery supply cutting off will depend upon the range selected. In case of 60 ma the unit can be operated only for very short time while for mv or thermocouple ranges it can be operated for little longer time. 2. FRONT PLATE DESCRIPTION 2.1 DISPLAY On front there is a 0.56", five digit, seven segment numerical display for indicating the value being simulated or measured. The unit of measurement is indicated by 3 mm discrete LEDs below the display. By selection of range and unit switches, particular unit LED will glow. One LED for 'BAT LO' is provided when the internal battery voltage drops below 6.75 volts. This LED operates only in battery mode of operation. Other LED for 'BAT CHG' is for indicating charging of the battery. 2.2 ADJUSTMENTS AND SETTINGS There are three 10 turn potentiometers on front. Two of them are marked "COARSE" and "FINE" corresponding to SPAN output. One of these marked "ZERO" is for adjusting mv and ma for the zero adjustment of the instrument under test. All the three potentiometers are common for either mv, V, ma or thermocouple simulation. For RTD simulation separate RTD simulator module is to be used. There is one more single turn potentiometer provided for ambient temperature adjustment. The ambient sensor is located just between the sense terminals for Operation Manual 5 of 19

6 proper tracking of ambient temperature for thermocouples. If any tracking error is observed, the ambient temperature can be adjusted by a screw driver. 2.3 TERMINALS There are six terminals provided on the front panel. These are standard terminals accepting 4 mm jacks directly. The "SOURCE" terminals are for mv or V output as well as mv output corresponding to the thermocouple types. For ma output there are two extra terminals marked "ma O/P" with current direction arrows. "SENSE" terminals are common for all measurements. RED terminals are for positive and BLACK terminals are for negative. For RTD and resistance measurement there are three combinations possible. For two wire measurements short ma O/P+ to SENSE+ and short ma O/P- to SENSE- terminal. Connect the RTD or resistance across SENSE terminals. For four wire measurement connect two wires of one end to ma O/P+ and SENSE+ and two wires of other end to ma O/P- and SENSE-. For three wire measurement, leave ma O/P- terminal open and connect other three terminals as per four wire connection. There is a built in circuit to detect 3W or 4W mode of operation. 2.4 PUSH BUTTON SWITCHES There are three groups of six push button switches each. One group is at bottom left corner which has push to ON, push to OFF type switches. The two groups in center are having inter linked switches in each group i.e. user can select only one of them at a time. Now we will see function of each of them BOTTOM SWITCHES PWR This switch is turning ON or OFF the instrument. In pressed condition instrument remains ON. UNIT This is the second switch in lower bank. It is not labeled, but the units for temperature measurement are selectable either as C or F. In OFF position deg.c is selected and in ON position deg.f is selected. Corresponding unit LED will glow in temperature display. DISP This switch is used to display ambient temperature with any range selected. The ambient will be displayed till the switch is in ON condition. When the switch is turned OFF the display will fall back to normal mode selected by other switches. The unit of ambient temperature is selected by UNIT switch. The ambient Operation Manual 6 of 19

7 temperature sensor is located just between the two "sense" terminals but due to self heating if any deviation in ambient is found facility for adjusting ambient is provided on front plate itself by a single turn potentiometer marked "AMB ADJ". CJC This switch is used for introducing cold junction compensation for thermocouple measurements. When the switch is ON means the mv output across the "SOURCE" terminals corresponding to the thermocouple type selected is ambient compensated, i.e. this is referred to the ambient temperature prevailing. When the switch is "OUT", the mv output corresponding to the thermocouple type is referred to 0 C. This switch eliminates need to refer thermocouple charts for ambient compensation. NUL This is provided for offset cancellation and differential measurement. For example, in case there is a zero drift in 20 mv range, and the unit reads few counts with the input shorted, one can NULL the same by pressing the NUL switch in. In all subsequent measurements, the initial count which was NULLED, will be subtracted. Make sure to turn OFF NUL switch after measurement is over, otherwise it will lead to erroneous readings in other ranges. The effect of NULLING is different in Pt-100 and Cu-53 ranges. In case of other ranges, it subtracts basic raw reading (before linearization in case of thermocouples), so if CJC switch is on, the reading will show ambient when NUL switch is pressed. For thermocouple types it subtracts mv at the time of NULL instead of temperature. In case of Pt-100 and Cu-53 ranges it subtracts actual temperature after linearization and calibration. O/P This switch is used to select between ZERO and SPAN settings. When this switch is pressed in, the output which is available across the "source" terminal will be corresponding to one set by 10 turn potentiometer marked 'ZERO'.With the switch in OUT position, the output available at the 'SOURCE' terminals will be COARSE and FINE potentiometers settable 'SPAN' settting. This facility is extremely useful for calibrations wherein quick simulation of zero and span is desired like 4 ma and 20 ma. Operation Manual 7 of 19

8 2.4.2 TYPE SELECTOR SWITCHES Two switch banks in the center of the instrument are used for selecting required input/output type. The left hand side group of six switches selects the basic input group type and the right hand side group of six switches selects range or type in the group selected by left hand side switch. The switches in right hand side group (now onwards referred as second group) have multiple functions. This functions are coded by different color legends matching with the switches in left hand side group (now onwards referred as first group). For selecting any type, one switch in either group has to be pressed. If the switch selection is invalid display will show "error" until a valid switch selection is made. TCB This is the first switch in RED color in first group. This switch is used for selecting BASE METAL type thermocouples. Exact thermocouple type is decided be the switch pressed in second group. These switches in second group are also marked in RED color for convenience. With TCB pressed in pushing any of the type switch will select the particular type and output will be available across "source" terminals. One can set E, J, K, T, SP1 and SP2 type thermocouples in this mode. SP1 and SP2 are default configured as K type from factory. If user has specially ordered for any other type of thermocouple, it will be programmed for that type and display will correspond to characteristic for that type. The output available across "source" terminals will be in mv and display will be in actual temperature. The source mv range will be from -50 mv to 250 mv in this type. TCN This is second switch in first group marked in BLUE color. When this switch is selected, mode will be corresponding to noble metal thermocouples B, R, and S types (selected by corresponding switches in second group in blue color). When TCN is pressed and in second group B, R or S is selected particular range will get selected and output will be available across the "source" terminals. The output available across "source" terminals will be in mv and display will be in actual temperature. The source mv range will be from -5 mv to 25 mv in this type. RTD This is third switch in first group marked in BLACK color. There are two standard RTD types Pt-100 and Cu-53 supported and resistance measurement upto 2K ohms with a resolution of 0.1 ohms is provided. For Pt-100 and Cu-53 the unit LED of deg.c or deg.f will glow according to range selection but for 2K range no unit LED will glow. For RTD there is automatic 3W/4W detection circuit provided within the unit itself. For 3W measurements just don't use the fourth terminal of current source negative. For RTD measurements a current source of 0.5 ma is used. Operation Manual 8 of 19

9 For simulation of RTD there is no provision within the instrument. It can only measure RTD temperature or resistance. For sourcing resistance one external RTD simulator module is supplied along with instrument. mv This fourth switch in first group marked in green color. There are two ranges 20 mv and 200 mv. 20 mv range is having a resolution of 1 micro volt and 200 mv range is having a resolution of 10 micro volts. Press the corresponding switch in second group for selecting either range. For 20 mv, source range is from -5 mv to 25 mv and for 200 mv, source range is from -50 mv to 250 mv. VOLTS This is fifth switch in first group marked as 'V' in green color. There are two ranges 2V and 10V. 2V range is having a resolution of 0.1 mv and 10V range is having resolution of 1 mv. Press the corresponding switch in second group for selecting either range. For 2V, source range is -0.5V to 2.5V and for 10V, source range is -2.5V to 12.5V. In case of 10V range, the stabilization time for reading will be few seconds because of input filter. CURRENT This is last switch in first group marked as 'ma' in green color. There are two ranges 20 ma and 60 ma. 20 ma range is having a resolution of 1 micro amp and 60 ma range is having a resolution of 10 micro amp. Press the corresponding switch in second group for selecting either range. For 20 ma source range is 0 ma to 25 ma. For 60 ma range the source is 0mA to 60 ma. In 60 ma range there is no over range. The instrument may show erroneous reading in 60 ma range, if you try to switch on with full current source. So, it will be advisable to switch on the instrument with low current and then increase the current gradually to full scale. This type of problem may come specially when battery voltage is low. While using 60 ma range be careful while making connections be cause excessive current may some time damage the unit under calibration. Compliance voltage of current source is specified as 24V and is valid for 20 ma range with mains operation or fully charged battery. If the battery voltage is low the voltage may be low. In case of 60 ma range the maximum compliance voltage at full scale may be about 20V. 2.5 EXAMPLES FOR USE Operation of any instrument can be best explained by examples. Few examples are given for various ranges. The schematic drawings for connections for this are also enclosed mv simulation Operation Manual 9 of 19

10 Select the switch marked mv in first group and 20 mv marked in second group. For 20 mv range due to thermal EMF in the instrument and the lead wire resistance of the internal wiring there can be a zero error in measurement. For using this range, first short the two sense terminals. The instrument may be reading a few microvolts. Press the null switch to make the reading zero at this point. Now, the zero error of instrument is compensated in this range. Now, remove the short across sense terminals and short source positive with sense positive and source negative with sense negative. Now the instrument is in simulation mode and you can set for required value by using COARSE and FINE pots V simulation Select the switch marked 'V' in first group and 10V marked in second group. Short the source and sense positive terminals and source and sense negative terminals. The output voltage will be displayed and will be available across the positive and negative terminals Setting 4 ma corresponding to ZERO and 20 ma corresponding to SPAN. Select the ma switch in first group and 20 ma range switch in second group. Short the two terminals marked 1 & 2 together and 3 & 4 together. Use COARSE and FINE pots to set the display to read ma. Now, press the ZERO/SPAN switch IN. Using the pot corresponding to ZERO, make the display to read ma. Now with the ZERO/SPAN switch in IN position instrument will source ma and with switch in OUT position it will source ma. For feeding this current to instrument under test, break the link between 1 & 2 and connect the instrument across these two terminals. The current path will get completed if the instrument is having a load resistance and the current will remain the same if it is not exceeding the compliance voltage range. If the reading shows zero, check the connections of the instrument, either the input terminals on instrument will be open or connection may be reverse. For feeding the current, user can connect the load across terminals 3 & 4 also with terminals 1 & 2 shorted by a link. The instrument will give same performance in both the methods of connections. After connecting the load calibrate the instrument under test by iterative switching of the ZERO/SPAN switch until both zero and span calibrations on the instrument under test are matching K type thermocouple simulation with ambient compensation. Let us try to set 1000 C for K type thermocouple with ambient compensation. Operation Manual 10 of 19

11 First press TCB and K switches to select the K type thermocouple. Also keep the CJC switch pressed. Short the two positive terminals of SOURCE and SENSE and two negative terminals of SOURCE and SENSE. Using the COARSE and FINE pots set the instrument to read 1000 C. Output mv available across source terminals will now be corresponding to 1000 C with mv subtracted for ambient temperature prevailing R type thermocouple simulation with ambient compensation. Let us try to set 1500 C for R type thermocouple with ambient compensation. First press TCN and R switches to select R type thermocouple. First short the sense terminals to see if there is any zero error in this range. If instrument is showing some reading with the terminals shorted, press NUL switch to cancel this. Now the instrument will read 0.0 temperature. Make sure, CJC switch is in out position. Now Press CJC switch IN and short the source and sense terminals. With the help of COARSE and FINE pots set the instrument to read C. Output mv available across source terminals will be corresponding to 1500C with mv for prevailing ambient subtracted PT-100 RTD measurement For this just press RTD and Pt-100 switches and connect the RTD across the terminals. Connection will depend upon whether the measurement is 3W or 4W. For 4W measurement connect all four leads and for 3W connect only first three terminals leaving fourth terminal open. The display will directly show the temperature in C or F depending upon the selection of unit Resistance simulation For simulation of resistance, select the 2K resistance range by pressing RTD and 2K switched. short terminals 1 & 2 and terminals 3 & 4. Connect terminals 2 & 3 to measure terminals of RTD simulator. With the RTD simulator switch in measure position, set the required resistance value by coarse and fine pots on the RTD simulator. The calibrator will read the resistance value. Now the switch can be turned to source position where the instrument under measurement can be connected. At this time a fixed resistance of 100 ohms is place across measure terminals so that the calibrator current source will not get open circuit. 3. CALIBRATION The instrument is calibrated at the factory for all the ranges with the help of a 6-1/2 digit or better multimeter. As a standard practice all calibrating instruments have to Operation Manual 11 of 19

12 be checked for deviation in calibration every year. This is necessary to compensate the effect of long term drift of the components used within the instrument. All the calibration parameters are stored in EEPROM inside the instrument. All necessary protections are made for protection of EEPROM data. Also there is a software algorithm included to give one level of protection against such disturbance. In spite of all these, due to heavy transients on the power supply or due to power fluctuations or noise in power line, if the calibration data gets disturbed, a warning is given. This warning is given by displaying a message "CALoF" for two seconds whenever a new range is switched. If this message is displayed, the instrument calibration is off and the reading accuracy is not guaranteed. In such a case it is better to recalibrate that particular range. The calibration procedure for the instrument is made very simple. The calibration is done at pre-defined points by just DIP switches. Before altering the calibration make sure to have proper instruments to calibrate this instrument. The multimeter to be used for cross checking it should be at least 5-1/2 digit with accuracy specifications better then this calibrator. For RTD/resistance calibration use decade BOX or resistance BOX with an accuracy of 0.01% or better. For calibration, first open the top cover by unscrewing the four screws on top. There is one horizontal card on the instrument called CPU card. On this card on the rear end, towards right there is one 4-way DIP switch. This switch is used for calibration purposes. For every range calibration point is fixed at a particular value listed in the table given in section CALIBRATION OF RANGES EXCEPT RTD Connect the output of the calibrator to a accurate multimeter and set it to the required value( Except for RTD types). If there is any deviation from the required value, turn ON the first two switches of the DIP switch. The instrument reading will match the reading indicated on standard multimeter within one/two seconds. If it is not matching, there can be something wrong with the instrument. If the difference between standard meter and calibrator is more than 5 % it will be unable to calibrate. Once the reading matches, put the switches back to OFF position. All the ranges can be calibrated one by one using this method. For 20 mv range and Noble metal thermocouple ranges ( B, R and S ), it is necessary to NULL the zero error before calibrating. Prior to calibrating first NULL the reading displayed with sense terminals shorted. Then remove the short and perform the same procedure like other types. 3.2 CALIBRATION OF RTD RANGES Operation Manual 12 of 19

13 In case of RTD types user has to feed the resistance from a standard resistance box or set it with the help of RTD simulator supplied and measure it on a standard multimeter. 3.3 AMBIENT CALIBRATION For ambient calibration, there is no need to open the instrument. It can be adjusted any time by means of a single turn pot marked "AMB ADJ" on front plate. 3.4 CALIBRATION POINTS RANGE MULTIMETER UNICAL READING READING 20 mv mv mv 200 mv mv mv 2 V V V 10V V V 20 ma ma ma 60 ma ma ma E t/c mv C * J t/c mv C * K t/c mv C * T t/c mv C * B t/c mv C * R t/c mv C * S t/c mv C * Pt ohm C Cu ohm C 2K ohm kohm kohm * CJC switch should be in off position. Note : For SP1 and SP2 calibration points are decided by the curve supplied by the user. Temperature calibration Standards as per IPTS COMMON CALIBRATION POINTS For some of the ranges calibration parameters are same. While calibrating, when one of the ranges is calibrated all the ranges in same group get calibrated. The grouping of ranges is as below a. 20 mv, B t/c, R t/c and S t/c b. E t/c, J t/c, K t/c and T t/c Operation Manual 13 of 19

14 c. Pt-100 and Cu BATTERIES The instrument is having six Ni-Cd batteries soldered on the power supply card at bottom. The batteries are automatically charged when mains supply is applied irrespective of the position of PWR switch. The charging indication is given by 'BAT CHG' LED on front plate. If the battery is fully discharged, keep it in charging for 14 to 16 hours before starting instrument on battery. The instrument is having built-in undervoltage cut-off circuit for battery operation. After BAT LO condition if the user continues to use the instrument for long period at one point of time instrument will stop functioning. In this condition still the unit draws few ma current from battery to keep the cut-off circuit active. So, PWR switch should be immediately switched off in this condition and the battery should be charged before reusing the unit. If the battery gets deep discharged, it may not be possible to charge it again and may get permanently damaged. When Ni-Cd cells get charged, there is a rise in internal temperature of the battery because of the energy pumped in the battery. So, the battery manufacturers recommend charging of the batteries to be performed at an ambient temperature below 40C. As such the instrument storage temperature specified is high, but it is advisable to store the instrument at a temperature below 40C for longer self life of the battery. 5. RTD SIMULATOR While Masibus UNICAL 3001M simulates and measures mv, Volts, ma and thermocouples, it only measures in RTD and resistance ranges. For simulating RTD and resistance a compact passive RTD simulator is provided which can be used with the UNICAL to calibrate RTD type of instruments. The procedure to check/calibrate RTD type of instruments is as follows 1. Connect the instrument under calibration as shown in drawing. 2. Switch on UNICAL and the instrument under test and allow some time for stabilization. 3. Select UNICAL for RTD mode by pressing RTD switch and the respective range. 4. Keep the RTD simulator MEASURE/SOURCE switch in 'MEASURE' position and adjust the desired reading by means of 'coarse' and 'fine' pots, reading the value on unical. Operation Manual 14 of 19

15 5. Once having set the potentiometer to the desired value, without disturbing the pot position throw the MEASURE/SOURCE switch in 'SOURCE' position. The resistance value adjusted on UNICAL will now be fed to the instrument under calibration. The RTD simulator can simulate resistance upto 2.1 k ohms. The COARSE potentiometer is of 2K and fine potentiometer is 100ohms. Both potentiometers are 10 turn for better resolution. FIGURE 1: mv, T/C OR Volt simulation mode SOURCE M + - Instrument under test Operation Manual 15 of 19

16 FIGURE 2: mv, T/C OR Volt measurement mode SOURCE SENSE M + - Signal to be measured FIGURE 3: Current measurement mode SOURCE ma o/p SENSE ma o/p M + - Current Signal to be measured Operation Manual 16 of 19

17 FIGURE 4: Current Simulation mode SOURCE ma o/p SENSE ma o/p M OR + - Instrument Under test SOURCE ma o/p SENSE ma o/p M + - Instrument under test Operation Manual 17 of 19

18 FIGURE 5: RTD 3 wire measurement mode SOURCE ma o/p SENSE ma o/p M RTD to be measured FIGURE 6: RTD 4 wire measurement mode SOURCE ma o/p SENSE ma o/p M FIGURE 7: RTD Simulation with RTD simulator RTD to be measured Operation Manual 18 of 19

19 SOURCE ma o/p SENSE ma o/p M INSTRUMENT UNDER CALIBRATION SOURCE MEASURE FINE COARSE RTD SIMULATOR Operation Manual 19 of 19