IOtech MultiScan 1200, User Manual

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168 Chapter 12: System Configuration TempScan / MultiScan User's Manual
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 Default Mode
To enable line-cycle integration / high-speed multi-channel mode, issue the following commands:
•
M#mode
: Select line-cycle integration / high-speed multi-channel mode, where
mode
is
0
.
•
W#wt
: Select the number of samples over which to average, where
wt
is the one of the following
weights:
1
,
2
,
4
,
8
,
16
,
32
(default),
64
,
128
, and
256
.
•
Y0,post,0
: Select the number
post
of Post-Trigger scans.
•
Cchans,type
: Select the channel number or range, and the scanning-card channel type(s).
•
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 .
Common Mode Voltage Inaccuracies
Inaccuracies can result if common mode voltages on adjacent channels are widely dissimilar. This
inaccuracy is due to inadequate settling time at the instrumentation amplifier when the unit is scanning
between channels. To eliminate these inaccuracies, the settling time can be increased using the
Set
Relay Make Time (
D#
) command. For more information on this command, see chapter API Command
Reference .