Scanning with External Instruments
In this configuration, you can use the DAQ970A for signal routing or control applications. If you install a
multiplexer plug-in module, you can use the DAQ970A for scanning with an external instrument. You can
connect an external instrument (such as a DMM) to the multiplexer COM terminal.
To control scanning with an external instrument, two control lines are provided. When the DAQ970A and
the external instrument are properly configured, you can synchronize a scan sequence between the two.
In this configuration, you must set up a scan list to include all desired multiplexer or multifunction chan-
nels. Channels which are not in the scan list are skipped during the scan. The instrument automatically
scans the list of channels in ascending order from slot 100 through slot 300.
For an externally-controlled scan, you must disable the internal DMM by pressing [Home] > User Settings
>DMMOff. Since the internal DMM is disabled, readings from multiplexer channels are not stored in
internal reading memory.
External connections are required to synchronize the scan sequence between the DAQ970A and the
external instrument. The DAQ970A must notify the external instrument when a relay is closed and settled
(including channel delay). The DAQ970A outputs a Channel Closed pulse from pin 5 on the rear-panel con-
nector. In response, the external instrument must notify the DAQ970A when it has finished its meas-
urement and ready to advance to the next channel in the scan list. The DAQ970A accepts a Channel
Advance signal on the External Trigger input line (pin 6).
You can configure the event or action that controls the onset of each sweep through the scan list (a sweep
is one pass through the scan list). When the DMMis disabled, the default scan interval source is "Auto"
(Immediate). For more information, refer to Scan Interval. You can configure the event or action that noti-
fies the DAQ970A to advance to the next channel in the scan list. Note that the Channel Advance source
shares the same sources as the scan interval. However, an error is generated if you attempt to set the chan-
nel advance source to the same source used for the scan interval.
You can specify the number of times the instrument will sweep through the scan list. When the specified
number of sweeps have occurred, the scan stops.
An externally-controlled scan can also include a read of a digital port or a read of the totalizer count on the
multifunction module. When the channel advance reaches the first digit channel, the instrument scans
through all the digital channels in that slot and stores the readings in reading memory (only one channel
advance signal is required).
Keysight DAQ970A User's Guide 133
[Channel] Menu Overview
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