Keithley 7708 User Manual page 24

4. Configure the Model 27xx for °C units, type K temperature sensor, and internal reference junction as follows:
a. Press SHIFT then SENSOR, and note the unit displays the temperature units: UNITS: C. (If necessary, use the cursor
and range keys to select °C units.)
b. Press ENTER. The unit then displays the sensor type: SENS: TCOUPLE.
c. Make sure that TCOUPLE is displayed, then press ENTER. The unit displays the thermocouple type: TYPE: J.
d. Select a type K temperature sensor, then press ENTER. The unit then displays the reference junction type: JUNC: SIM.
e. Select INT reference junction, then press ENTER.
5. Source each of the voltages summarized in
select the appropriate thermocouple type for each group of readings. (See step 3 above.) Open Channel 1 after the test is
completed.
Table 6
Thermocouple temperature verification reading limits
Thermocouple type Applied DC voltage*
J -7.659mV
0mV
42.280mV
K -5.730mV
0mV
54.138mV
*Voltages shown are based on ITS-90 standard.
RTD temperature
1. Connect the precision decade resistance box (listed in
four-wire connections. (See
2. Install the Model 7708 in Slot 1 of the Model 27xx, turn on the power, and allow the unit to warm up for two hours before
proceeding. Be sure the front panel INPUTS switch is set to the REAR position.
3. Select the temperature function by pressing the TEMP key. Close Channel 1 by pressing the CLOSE key and keying in
101.
4. Configure the Model 27xx temperature function for °C units and RTD temperature sensor (α=0.00385) as follows:
a. Press SHIFT then SENSOR, and note the unit displays the temperature units: UNITS: C.
b. Press ENTER, and note the unit displays the sensor type: SENS: TCOUPLE.
c. Using the cursor and range keys, set the display as follows: SENS: 4W-RTD.
d. Press ENTER, and note the unit displays: TYPE: PT100.
e. Using the cursor and range keys, set the unit for the following display: TYPE: PT385.
f. Press ENTER to complete the temperature configuration process.
5. Set the decade resistance box to each of the values shown in
the required limits. Open Channel 1when finished.
Table 7
Plug-in module four-wire RTD temperature verification reading limits
Applied resistance*
22.80Ω
100.00Ω
313.59Ω
*Based on α = 0.00385. See text.
20
Table 6
Reading limits (1 year, 18°C to 28°C)
-192.33 to -187.67°C
-1.0 to +1.0°C
749.0 to 751.0°C
-192.33 to -187.67°C
-1.0 to +1.0°C
1349.0 to 1351.0°C
Figure 11 for similar connecting scheme.)
Reading limits (1 year, 18°C to 28°C)
-190.06 to -189.94°C
-0.06 to +0.06°C
599.94 to 600.06°C
and verify that the temperature readings are within limits. Be sure to
Table 2) to the Model 7708 CH1 and CH21 H and L terminals using
Table 7, and verify that the temperature readings are within