VXI VT1422A - Manual (Page 166)

164 Advanced Programming with the VT1529B Chapter 5
For example, the existing SCPI commands to measure thermocouples with
a VT1508A SCP and the VT1422A are:
SENS:REF THER,5000,(@108)
Sense the reference temperature
on channel 108 using a 5k
thermistor
SENS:FUNC:TEMP TC,J,(@109:111)
Indicates channels 109 through
111 are type J thermocouples
SENS:REF:CHAN (@108),(@109:111)
Specifies channel 108 as the
isothermal reference for
channels 109 through 111
ROUT:SEQ:DEF (@108:111)
Sets scan list to include the
reference and the thermocouples
INIT
Start scan
To measure thermocouples using the VT1529B and VT1586A using the
new commands:
SENS:REF:POST THER,5000,(@10000),(@10001)
Specifies that the reference
thermistor voltage is on channel
10001 and its excitation voltage
is on channel 10000
SENS:FUNC:TEMP:POST TC,J,(@10003:10005)
Indicates channels 10003
through 10005 are type J
thermocouples
SENS:REF:CHAN:POST (@10001),(@10003:10005) Specifies channel 10001 as the
isothermal reference thermistor
for channels 10003 through
10005
ROUT:SEQ:DEF (@10003:10005,10001,10000)
Sets scan list to include the
thermocouples, the reference
thermistor and excitation voltage
INIT
Start scan
Similarly, the VXIplug&play call to read the FIFO data changes from:
hpe1422_readFifo_Q(vi, 1000)
Read 1000 readings
to
hpe1422_readFifoPost_Q(vi, 2, 0, 65024, f64_array)
Read 2 scans of data,
post-convert to EU, no extra
data in FIFO from algorithms
Strain Measurements
With the VT1529A, the excitation voltages are measured once prior to the
start of scanning (INITiate:IMMediate command). The measured value is
then sent to the DSP for use in the on-the-fly EU conversions. Therefore, for
long tests, for the best possible accuracy, the excitation supply must be both
long-term and short-term stable.
With the VT1529B, the excitation voltage can be measured during each scan
and the VXIplug&play driver can use updated measurements for the
conversions. This provides better accuracy and uses a less expensive
excitation supply.