IOtech MultiScan 1200, Руководство пользователя

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TempScan / MultiScan User's Manual Chapter 12: System Configuration 169
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 the chapter 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 the chapter 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 the chapter 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 chapter API Command Reference .