VXI VT1422A - Manual (Page 116)

114 Programming the VT1422A for Data Acquisition and Control Chapter 4
Thermocouple Measurements
Thermocouple measurements are voltage measurements that the EU
conversion changes into temperature values based on the <sub_type>
parameter and latest reference temperature value.
•
For Thermocouples the <sub_type> parameter can specify CUSTom,
E, EEXT, J, K, N, R, S, T (CUSTom is pre-defined as Type K, no
reference junction compensation; EEXT is the type E for extended
temperatures of 800
° F or above).
To set channels 32 through 40 to measure temperature using type E
thermocouples:
SENS:FUNC:TEMP TC, E, (@132:140)
(see following section to configure a TC reference measurement)
Thermocouple Reference Temperature Compensation
The isothermal reference temperature is required for thermocouple
temperature EU conversions. The Reference Temperature Register must be
loaded with the current reference temperature before thermocouple channels
are scanned. The Reference Temperature Register can be loaded two ways:
1. By measuring the temperature of an isothermal reference junction
during an input scan.
2. By supplying a constant temperature value (that of a controlled
temperature reference junction) before a scan is started.
Setting up a Reference Temperature Measurement
This operation requires two commands, the [SENSe:]REFerence command
and the [SENSe:]REFerence:CHANnels command.
The [SENSe:]REFerence <type>, <sub_type>,[<range>,](@<ch_list>)
command links channels to the reference temperature EU conversion.
•
The <ch_list> parameter specifies the sense channel that are
connected to the reference temperature sensor.
•
The <type> parameter can specify THERmistor, RTD, or CUSTom.
THER and RTD, are resistance temperature measurements and use the
on-board 122 µA current source for excitation. CUSTom is
pre-defined as a Type E thermocouple which has a thermally
controlled ice point reference junction.