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 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