Analog trigger with PXI 6281

[christophe.A]

Hi everyone,

I have received from NI France a PXI 6281 with SCB 68 connector. My objective is to realize an analog triggering on tension levels (which are in fact Amps).

I have linked tension measurement device to ai1 (+) and ai/gnd (-).

Ai1 (+) is linked by another cable to APFI0 on the SCB connector.

I use an example program (Daqmx analog comparison attached) to export Analog Comparison Event to a PFI line.

I recorded the tension level and the output of the PFI line below (see graph) and I have 2 questions :

-why is the tension level at 5V by default and how can I put it to 0V ?

-why does the PFI line outputs 2.5V only and not 5V ? Randomly, it outputs 5V though.

Thanks in advance,

Christophe Baud

[Romain_Duval]

hello Christophe,

The reason why the PFI line is outputting 5V by default is explained in this document: opencollector, push pull configuration

Thus I think you can use the channel property node to specify the default voltage level.

For the 2.5 voltage level, you say it output 5V randomly. Did you check the wiring of your cable?