ADLINK Technology NuPRO-935A User Manual download pdf (Page 29)

Operation Theorem • 23

is the default debounce time for a switch module, i.e. 5ms for PXI-7921. T

is the user specified scan delay time in the scanlist entry, indicating the time

between the relay being debounced and the exact moment that a measurement

device takes a new measurement. The actual delay time would be the greater

of the two times, to guarantee that measurement devices take measurements

after the signal path is fully settled, and the relays switch as close as possible to

their maximum operating speed.

As the scan delay time elapses, the switch module generates Scanner

Advanced signal to inform the measurement device to take a new

measurement.

After the measurement completes, the measurement device will generate

another Trigger In signal to have the switch module update the relay pattern to

that specified in the second entry of scanlist.

The handshaking process will continue, until it reaches the end of the scanlist

(if one-time scanning mode is selected), or when a software scan-abort

command is received.

Connecting, Trigger and Synchronize with External DMM

In this example, Agilent

33401A 6-1/2 Digital Multimeter (DMM) is used to

demonstrate signal connection for handshaking operation.

The DMM provides two terminals on the rear panel for the handshaking

operation process, Trig In and VM Comp. The Trig In connects to the Scanner

Advanced output on switch module, while the VM Comp to Trigger In. If the

terminal board is used, wire Trig In to TRG_IN on terminal board, and the VM

Comp to S_ADV.

Follow the instructions below to ensure the handshake functions properly:

1. Configure ADLINK PXI switch module’s Trigger In to rising-edge

triggered, Scanner Advanced output in active-low pulsating

mode with pulse width of at least 2us.

2. Configure the DMM to wait for external Trig In before a

measurement, and generate VM Comp after a measurement.

Arm the DMM to wait for the first trigger.

3. Setup the scanlist and auto-scan mode. The first entry in the

scanlist should be set disable wait for the Trigger In, but enable

Scanner Advanced output. Succeeding entries should enable

both Trigger In and Scanner Advanced output. Download the

scanlist to the switch module afterward.

4. Start auto-scan by sending scan start command to the switch

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ADLINK Technology NuPRO-935A User Manual Page 29