VXI VT1422A - Manual (Page 117)

Programming the VT1422A for Data Acquisition and Control 115 Chapter 4
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The <sub_type> parameter must specify:
-- For RTDs; "85" or "92" (for 100 ohm RTDs with 0.00385 or
0.00392 ohms/ohm/°C temperature coefficients respectively)
-- For Thermistors; only "5000" (See previous note on page 113)
-- For CUSTom; only "1"
•
The optional <range> parameter can be used to choose a fixed A/D
range. When not specified (defaulted) or set to AUTO, the module
uses auto-range.
Reference Measurement Before Thermocouple Measurements
At this point, the concept of the VT1422A Scan List will be introduced. As
each algorithm is defined, the VT1422A places any reference to an analog
input channel into the Scan List (this is in addition to those channels
specified by the ROUT:SEQ:DEF command, see "Defining an Analog Input
Scan List" on page 123). When the algorithms are run, the scan list tells the
VT1422A which analog channels to scan during the Input Phase.
The [SENSe:]REFerence:CHANnels (@<ref_chan>),(@<meas_ch_list>)
is used to place the <ref_chan> channel in the scan list before the related
thermocouple measuring channels in <meas_chan>. Now when analog
channels are scanned, the VT1422A will include the reference channel in the
scan list and will scan it before the specified thermocouples are scanned.
The reference measurement will be stored in the Reference Temperature
Register. The reference temperature value is applied to the thermocouple EU
conversions for thermcouple channel measurements that follow.
A Complete Thermocouple Measurement Command Sequence
The command sequence performs these functions:
•
Configures reference temperature measurement on channel 15.
•
Configures thermocouple measurements on channels 16 through 23.
•
Instructs the VT1422A to add channel 15 to the Scan List and order
channels so channel 15 will be scanned before channels 16 through 23.
SENS:REF THER, 5000, (@115)
5k thermistor temperature for
channel 15
SENS:FUNC:TEMP TC,J,(@116:123)
Type J thermocouple
temperature for channels 16
through 23
SENS:REF:CHAN (@115),(@116:123)
reference channel scanned
before channels 16 - 23