VXI VT1422A - Manual (Page 125)

Programming the VT1422A for Data Acquisition and Control 123 Chapter 4
Re-Execute
*CAL? When:
•
When channel gain and/or filter cut-off frequency on programmable
SCPs are changed (using INPut:GAIN or INPut:FILTer...).
•
When SCPs are re-configured to different locations. This is true even
if an SCP is replaced with an identical model SCP because the
calibration constants are specific to each SCP channel’s individual
performance.
•
When the ambient temperature within the mainframe changes
significantly. Temperature changes affect accuracy much more than
long-term component drift. See temperature coefficients in Appendix A
page 419 "Specifications."
NOTE
To save time when performing channel calibration on multiple VT1422As
in the same mainframe, use the CAL:SETup and CAL:SETup? queries (See
“CALibration:SETup” on page 268. for details).
Calibrating Remote
Signal Conditioning
Units
RSCUs have a local calibration source that the VT1422A can measure
directly. This source voltage along with a local short can be fed to each
channel on the RSCU. The VT1422A reads the output value of each remote
channel when connected to the short and then the calibration voltage source.
Using this method, the VT1422A can determine the offset and gain values
for each remote channel. Further, these values can be stored in non-volatile
memory in the RSCU. The commands used to perform the remote
calibration are: CALibration:REMote (@<ch_list>) where <ch_list> need
only contain the first channel on each RSCU to calibrate all channels on that
RSCU. The command to store the calibration constants into non-volatile
memory is: CALibration:REMote:STORe (@<ch_list>) where <ch_list>
need only contain the first channel on each RSCU to store the calibration
constants into non-volatile flash memory.
Defining an Analog Input Scan List (ROUT:SEQ:DEF)
In this programming step, the contents of the analog input Scan List will be
defined using the ROUTe:SEQuence:DEFine command. This allows
measurements to be made that will be stored to the Current Value Table
(CVT) and/or the FIFO buffer without programming or executing any
algorithms. While the VT1422A can be used exclusively in this way, these
modes of operation can also be combined (scanned analog input and
algorithmic acquisition-and-control). In fact, there is only a single analog
input scan list and it is defined as the sum of channels specified by
ROUT:SEQ:DEF and referenced in any algorithms downloaded with the
ALG:DEF SCPI command or the hpe1422_downloadAlg(...) plug&play
function. Duplicate channel references are discarded. No matter how many
times a channel is referenced, it is only measured once per trigger and the
same value is seen in storage and by algorithms.