Measurement Computing TempScan/1100 - Manual (Page 63)

TempScan / MultiScan User's Manual 879596 System Configuration 4-5
Single-Channel High-Speed Burst Mode
In single-channel high-speed burst mode, the MultiScan/1200 unit can sample and store data from 38.5 Hz
to 20 kHz. When performing post-acquisition waveform analysis such as Fast Fourier Transforms (FFTs),
the unit can return the data points to your program in a waveform. As an alternative, the unit can provide a
true RMS (Root Mean Square) value of the equivalent AC voltage.
Due to the high sampling rates achievable in single-channel high-speed burst mode, the posting of the
High/Low/Last (HLL) Registers and the alarms is disabled. Also, for the same reason, the Trigger (trigger
start event) can only be set to the software Trigger On (
@ ) command, the Stop (trigger stop event) can only
be set to Count (validating the Set Counts ( Y ) command), and the following items are not permitted: Pre-
Trigger, Post-Stop count, scan time stamping, and scan alarm stamping. For more information, see
command Set Trigger Configuration (
T ) in Appendix A- API Command Reference.
In single-channel high-speed burst mode, the MultiScan/1200 internally collects the samples for the
selected channel in 256-sample blocks. However, this externally appears the same as 256-channel scans in
the line-cycle integration / high-speed multi-channel mode. That is, when you program the number of 256-
sample blocks in the Post-Trigger count parameter
post of the Set Counts ( Y ) command, you will retrieve
the data from the MultiScan/1200 unit as "Post-Trigger count" scans of 256 samples. For more
information, see command Set Counts (
Y ) in Appendix A- API Command Reference.
For AC voltage measurements in burst mode, the RMS value can be retrieved with the
U17 query
command upon completion of the acquisition.
Note: The single-channel high-speed burst mode is a one-shot operation, since it collects the
specified number of samples and stops. It is not continuous, and does not allow memory
overflow and wrap-around. The maximum amount of samples which can be taken is dictated
by the amount of memory available. See command Set Counts (
Y ) in Appendix A-
API Command Reference.
Note: The MultiScan/1200 unit only supports the measurement of AC voltages where the frequency
of the input signal is an integer multiple of the AC line cycle. Consequently, sampling
weights less than 32 can yield incorrect results. In order to compute an accurate Vrms value,
you must program a frequency which will yield a sufficient even integer number of samples
per line cycle.
To Enable the Burst Mode
To enable single-channel high-speed burst mode, issue the following commands:
•
M#mode : Select single-channel high-speed burst mode, where mode is 1 .
•
F#freq : Select the burst mode sampling frequency, where freq is a real number between 38.5 and
20000 Hz (default).
•
Y0,post,0 : Select the number post of 256-sample blocks to acquire, where post is limited by the
amount of memory available.
•
Cchans,type : Select the channel number and the scanning-card channel type.
•
Tstart,stop,0,0 : Set the Trigger (trigger start event) to the software Trigger On ( @ ) command,
where start is 1 ; and set the Stop (trigger stop event) to Count, where stop is 8 . The Set Counts ( Y )
command is made valid when the Stop is set to Count.
•
@ : Start the acquisition.
For more information on the above commands, see Appendix A- API Command Reference.