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Operating and Programming 3
L4400 User’s Guide 69
The following command clears all user- defined channel labels on the
instrument and restores the factory- default labels.
ROUT:CHAN:LABEL:CLEAR:MOD 1
Scanning Applications
Usage:
• L4421A 40- Channel Armature Multiplexer
• L4450A 64- Bit Digital I/O (digital input, counter channels only)
• L4452A Multifunction Module (digital input, totalizer channels only)
Channels on selected L4400 series instruments can be “scanned” by separate
devices such as a DMM. During a scan, the instrument channels are
connected to the device and a measurement/reading is made one channel at
a time. Once the measurement is complete, the scan advances to the next
channel in the list until the end of the scan list is reached and the number of
passes (sweeps) through the scan list is complete.
For scanning applications involving the L4421A and a DMM, readings are
stored on the DMM. For applications involving scans of the digital input and
counter channels of the L4450A and the digital input and totalizer channels
of the L4452A, readings are stored in L4450A/L4452A memory.
Scanning is not allowed with the other (L4433A, L4437A, L4445A) switching
instruments. Also, scan lists cannot include digital output channels or DAC
voltage channels.
Rules for Scanning
• Before you can initiate a scan, you must set up a scan list to include all
desired multiplexer or digital channels. Channels which are not in the
scan list are skipped during the scan. By default, channels are scanned in
ascending order. If your application requires non- ordered scanning of the
channels in the present scan list, see “Non- Sequential Scanning" on
page 79.
• You can store at least 500,000 scan readings in instrument
(L4450A/L4452A) memory and all readings are automatically time
stamped. If memory overflows, a status register bit is set and new
readings will overwrite the first (oldest) readings stored. The most recent
readings are always preserved. Using the DATA:REMove? or R? command
to retrieve readings during a scan REMOVES the readings from memory.
Using FETCh? after the scan completes retrieves the readings and the
readings also remain in instrument memory.