Agilent Technologies E1476A User Manual page 48

Chapter 2
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The procedure to make temperature measurements is:
1 Measure the resistance of the 5 KΩ thermistor on the terminal module
(7KUBRKPV). A 4-wire ohms measurement should be made to avoid
measurement errors by the 100Ω protection resistors (see "Example:
Four-Wire Resistance Measurements").
2 Compute the temperature of the terminal module (7UHI) from the
reading (7KUBRKPV). For values of resistance between 92.7 Ω to
3.685E6 Ω, use the following equation to calculate the temperature
of the terminal module, where 7UHI = temperature in degrees C and
7KUBRKPV = the resistance of the 5 KΩ thermistor, W = ln (7KUBRKPV),
$ = 1.28463E-3, % = 0.23625E-3, and & = 9.2697E-8.
7UHI ^  $  : %  & : : `  
3 Measure voltage on the thermocouple connected to a channel (9W).
4 Compute the effective temperature at the external thermocouple
junction by doing the following two steps:
•
Compute the actual voltage across the external thermocouple
junction using 9WF 7H[WHUQDO
actual voltmeter reading and 9WF 7UHI is the voltage across the
selected thermocouple type at the terminal module temperature
(7UHI). This voltage must be evaluated from tabular data for the
selected thermocouple.
•
Evaluate the actual thermocouple temperature using the
9WF 7H[WHUQDO value and the tabular data for the selected
thermocouple.
5 Compute the compensated voltage (V) by the formula: 9
6 Convert the compensated voltage (V) calculated in Step 4 to
temperature. This is the actual temperature measured by the
thermocouple.
9 PHWHU  9WF 7UHI where9 PHWHU is the
Switchbox Applications 47
9W9UHI .