Trigger usage on cDAQ-9185 and NI-9401

[rusty21]

Hi all,

I have a cDAQ 9185 & NI-9401 to measure digital signals. ctr0 is used
for edge separation, ctr2 & ctr3 to measure frequencies, which works well.
I need to add one trigger condition for all 3 ctrs.
This trigger signal could be done with e.g. ctr1 (unused).
The Test.vi with trigger for ctr0 throws the error message -200077 for startTask ctr0,
after the VI has been terminated. A trigger signal on PFI5 shows no effect,
no more data is read.
Someone has an idea what is going wrong here?

Thanks for your kind help.

[Kevin_Price]

1. For whatever reason, counter *input* tasks don't support the use of a regular Start Trigger.  You need to configure for an "Arm Start" Trigger instead using a DAQmx Trigger property node. 

2. You'll need to do the same for the other counters if you want them to be started at the same time.  Make sure all tasks are started before the trigger can assert.

3. However, you'll still be left with some uncertainty.  You won't be able to know how much time passes between the trigger and the first active edge that starts your frequency measurement.  Whether or not you can know that for the semiperiod measurement is device-dependent.

-Kevin P

[rusty21]

Hi Kevin_P,

thank you very much for your explanation. The "arm trigger" thing is new to me, I'll have to deal with that first.
The hint about some uncertainty is valuable, but luckily not time critical in my application.

Thanks a lot

[Kevin_Price · Accepted solution]

Here's what it looks like to configure an "Arm Start" trigger:

-Kevin P