HP 34970A User Manual page 95

Chapter 4 Features and Functions
Scanning With External Instruments
In this configuration, you must set up a scan list to include all desired
multiplexer or digital channels. Channels which are not in the 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 either remove the internal
from the HP 34970A or disable it (see "Internal DMM Disable" on
DMM
page 145). Since the internal DMM is not used, readings from
multiplexer channels are not stored in internal reading memory.
External connections are required to synchronize the scan sequence
between the HP 34970A and the external instrument. The HP 34970A
must notify the external instrument when a relay is closed and settled
(including channel delay). The HP 34970A outputs a Channel Closed
pulse from pin 5 on the rear-panel connector (see previous page).
In response, the external instrument must notify the HP 34970A when
it has finished its measurement and is ready to advance to the next
channel in the scan list. The HP 34970A 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 internal DMM is removed (or disabled), the default scan
interval source is "timer". For more information, refer to "Scan Interval"
on page 80.
You can configure the event or action that notifies the HP 34970A 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 channel
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. For more information, refer to "Scan Count"
on page 86.
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