Chapter 4 Features and Functions

ScanningScanning

The instrument allows you to combine a DMM (either internal or external) with multiplexer channels to create a scan. During a scan, the instrument connects the DMM to the configured multiplexer channels one at a time and makes a measurement on each channel.

Any channel that can be “read” by the instrument can also be included in a scan. This includes any combination of temperature, voltage, resistance, current, frequency, or period measurements on multiplexer channels. A scan can also include a read of a digital port or a read of the totalizer count on the multifunction module. Scanning is allowed with the following modules:

∙HP 34901A 20-Channel Multiplexer

∙HP 34902A 16-Channel Multiplexer

∙HP 34907A Multifunction Module (digital input and totalizer only)

∙HP 34908A 40-Channel Single-Ended Multiplexer

Automated scanning is not allowed with the actuator module, the matrix module, or the RF multiplexer modules. In addition, a scan cannot include a write to a digital port or a voltage output from a DAC channel. However, you can write your own program to manually create a “scan” to include these operations.

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. The instrument automatically scans the list of channels in ascending order from slot 100 through slot 300. Measurements are taken only during a scan and only on those channels which are included in the scan list. The “ ” (sample) annunciator turns on during each measurement.

∙You can store up to 50,000 readings in non-volatile memory during a scan. Readings are stored only during a scan and all readings are automatically time stamped. If memory overflows (the MEM annunciator will turn on), a status register bit is set and new readings will overwrite the first readings stored (the most recent readings are always preserved). You can read the contents of memory at any time, even during a scan. Reading memory is not cleared when you read it.

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