Keithley 7708 User Manual page 23

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 verify the accuracy of temperature measurements. As long as the DC volts
and resistance functions meet or exceed specifications, temperature function accuracy is automatically verified. However, tem-
perature 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 7708 CH1 H and L INPUT termi-
nals using low-thermal shielded connections, as shown in
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.
Figure 13
Connections for thermocouple temperature verification
CH1
H L
H L H L H L
CH2 CH3 CH4
CH1
Notes: This setup and reading limits
table does not include errors
from ice point, thermocouple
wire, and connections.
HI and LO connections from
the calibrator and Model 7708
must be electrically isolated
from each other.
H L
H L
CH1 CH2
H L H L H L H L
H L H L H L H L H L
CH5 CH6 CH7 CH8 CH9 CH10 CH11 CH12 CH13
Model 7708
Thermocouple
Make HI and LO
Connections
in Ice Bath
Figure 13.
Output
HI
H L
CH14
Twisted
Wire
Ice Bath
Calibrator (Output DC Voltage)
Output
LO
Low Thermal
Copper Connection
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