Export the trigger for Scope to DMM

[Pietro7]

Hi Nathan and NI Community

First of all thank you for the help and a happy new year!

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@Nathan-P wrote:

If you want the DMM to start taking measurements on the "Analog Edge Reference Trigger"...

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Yes, this is exactly what I want the software to do.

I see the differences between the timing of the exported signals, the diagram helped me to understand. So I changed the input on the "niScope export triggers VI" to "reference trigger" but it changed anything in the behavior of the program. Neither when I select "end of record event" or an other of the options...

Here is an example: In the moment when the Measurement VI (which includes the Scope and the DMM, see the attachment of my previous post) is called, a current of 20V lays on the pins of the DMM. After it has been called and it runs, it waits for the trigger on the Scope. Then I change the current to 5V. As soon as the trigger occurs, the Scope makes the record as configured but the DMM gives me the "old" value of 20V (initialization of the Measurement VI) instead of the now correct 5V.

Does it still have something to do with the initialization of the tasks? I also tried to insert sequence structures... Or do you see an other error or a way to solve the problem?

Regards

Pietro

[cheggers · Accepted solution]

Hi all,

the PXI-4065 has a minimum trigger input pulse width of 200ns (see specification). The PXI-5114 has a (output) trigger pulse width ranging from about 40...90ns depending on the sample rate (for exact values export the trigger and measure it with a scope). So this value is under the specification of the 4065 (it can still be that the 4065 can catch the trigger but we can only guarantee what is specified).

There are the folllowing possibilities:

1. Measure continously with the DMM (instead of one triggered single-point). The scope will give you the timestamp of the trigger. Find the DMM data at this timestamp

- Precision is only in the ms range (for example 100ms)

- The software needs changes

+ No additional HW costs

+ No external wiring needed

2. Use an additional DAQ device. Send the trigger from the scope to a DAQ card that could then output an appropriately sized pulse to the DMM

- Additional HW costs

- Adding additional counter task to the SW

+ Precision is in the ns range

+ High chance that DAQ dev. will be reused in another application

+ No external wiring needed

3. Build a custom trigger electronic board (for example schmidt-trigger...) which outputs a pulse >200ns when the analog threshold is crossed.

- External wiring needed

- Custom board needs to be designed

+ Precision is in the ns range

Greetings,

Sascha Egger

Applications Engineer Group Leader Switzerland