Keithley 2700, Service Manual

Page: 43 / 174

Performance Verification 1-27
Verifying temperature
Thermocouple, thermistor, and RTD temperature readings are derived from DC volts and
resistance measurements respectively. For that reason, it is not necessary to independently ver-
ify the accuracy of temperature measurements. As long as the DC volts and resistance functions
meet or exceed specifications, temperature function accuracy is automatically verified. How-
ever, temperature verification procedures are provided below for those who wish to separately
verify temperature accuracy.
Thermocouple temperature
1. Connect the DC voltage calibrator output terminals and ice point reference to the
Model 7700 CH1 H and L INPUT terminals using low-thermal shielded connections, as
shown in
Figure 1-14 .
2. Install the Model 7700 in Slot 1 of the Model 2700, then 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 press-
ing the CLOSE key and keying in 101.
4. Configure the Model 2700 for °C units, type K temperature sensor, and internal refer-
ence 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.
Table 1-13
Limits for plug-in module resistance verification
Ω
Range
Nominal resis-
tance Nominal reading limits
(1 year, 18°C to 28°C)
Recalculated limits**
100
Ω∗
1k
Ω
10k
Ω
100k
Ω
1M
Ω
10M
Ω
100M
Ω
100
Ω
1k
Ω
10k
Ω
100k
Ω
1M
Ω
10M
Ω
100M
Ω
99.9884 to 100.0116
Ω
0.999894 to 1.000106k
Ω
9.99894 to 10.00106k
Ω
99.9890 to 100.0110k
Ω
0.999890 to 1.000110M
Ω
9.99590 to 10.00410M
Ω
99.5770 to 100.4230M
Ω
__________ to __________
Ω
__________ to __________ k
Ω
__________ to __________ k
Ω
__________ to __________ k
Ω
__________ to __________ M
Ω
__________ to __________ M
Ω
__________ to __________ M
Ω
* Enable OCOMP for 100
Ω
range.
** Calculate limits based on actual calibration resistance values and Model 2700 one-year resistance accuracy specifications. See
Verification limits .