Strain Measurements - VXI VT1422A User Manual

Strain Measurements

164 Advanced Programming with the VT1529B
For example, the existing SCPI commands to measure thermocouples with
a VT1508A SCP and the VT1422A are:
SENS:REF THER,5000,(@108)
SENS:FUNC:TEMP TC,J,(@109:111)
SENS:REF:CHAN (@108),(@109:111)
ROUT:SEQ:DEF (@108:111)
INIT
To measure thermocouples using the VT1529B and VT1586A using the
new commands:
SENS:REF:POST THER,5000,(@10000),(@10001)
SENS:FUNC:TEMP:POST TC,J,(@10003:10005)
SENS:REF:CHAN:POST (@10001),(@10003:10005) Specifies channel 10001 as the
ROUT:SEQ:DEF (@10003:10005,10001,10000)
INIT
Similarly, the VXIplug&play call to read the FIFO data changes from:
hpe1422_readFifo_Q(vi, 1000)
to
hpe1422_readFifoPost_Q(vi, 2, 0, 65024, f64_array)
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.
Sense the reference temperature
on channel 108 using a 5k
thermistor
Indicates channels 109 through
111 are type J thermocouples
Specifies channel 108 as the
isothermal reference for
channels 109 through 111
Sets scan list to include the
reference and the thermocouples
Start scan
Specifies that the reference
thermistor voltage is on channel
10001 and its excitation voltage
is on channel 10000
Indicates channels 10003
through 10005 are type J
thermocouples
isothermal reference thermistor
for channels 10003 through
10005
Sets scan list to include the
thermocouples, the reference
thermistor and excitation voltage
Start scan
Read 1000 readings
Read 2 scans of data,
post-convert to EU, no extra
data in FIFO from algorithms
Chapter 5