Handshaking

NI Switches Help

Edition Date: April 2015

Part Number: 375472H-01

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Handshaking allows the DMM and switch to take measurements without controller interaction. The controller periodically acquires data from the DMM at a user-specified interval. Handshaking frees the controller for other tasks and takes measurements faster than immediate operations mode. The handshaking trigger is sent from both DMM to switch and switch to DMM. This differs from synchronous mode, in which only one trigger is sent from the DMM to switch. Scanning is faster in handshaking mode; therefore, handshaking is recommended over synchronous mode when using NI products.

With handshaking, the DMM is initiated and waiting for a trigger. The switch module is initiated, executes the first connection in the scan list, and generates a digital pulse—Scan Advanced (SA) signal. The DMM receives this signal from the switch, takes a measurement, and then generates a digital pulse—measurement complete (MC). When the switch receives the digital pulse, it advances to the next entry in its scan list. After the relays of the switch module have settled, the switch sends a digital pulse and triggers the DMM for a new measurement. Refer to the Multiple Point Acquisitions topic in the NI Digital Multimeters Help at ni.com/manuals to determine the triggering options. The following figure represents a handshaking process between a switch module and DMM (instrument).

Note Note  Some devices may not support scanning. Refer to your device book for more information about supported features.

The following figure shows a handshaking timing diagram.

where

M = measurement

WFT = wait for trigger

S&S = switch and settle

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