Export the trigger for Scope to DMM

[Pietro7]

Hi

I would like to export the trigger Signal, which I get on the Channel 0 of the Scope, to a DMM in a PXI System.

So far, the Scope does what I want it to do (Acquisition of 1 Record with a length of 550000 at a Sample Rate of 50kHz with a Pretrigger of 1s).

I would need to know the measurement value of the DMM at the Scope triggerevent. For this I inserted the "export signal.vi" to the scope and set it to reference trigger and as output terminal i choose "PXI Trigger Line 0/RTSI0". On the DMM I set the Trigger Source to "TTL0" which should correspond to the Line on which I'am exporting the Signal of the Scope.

But it doesn't work. The DMM sends out the value as soon as I start the vi (it doesn't wait for the Triggerevent). If I choose "none" as signal to export in the scope, the DMM waits until it goes into a Timeout. Do I have to set up something differently or do I have to use the TCIk vi's?

Thanks for your Inputs!

Pietro

[HoussamK]

Hi,

could you please post you code?

Are you using two separate VIs ? Did you initiate your Slave (DMM) before your Master (scope)  ?

[Pietro7]

Hi hsm78

Thank you for your reply and for the input.

Yes, I use separate Sub VI's for the Scope and the DMM. But it would be no problem to merge them if it makes the synchronization easier. In both VI's I' Initialize the Instruments separately. Does it depend when I initialize which device? Probably it is an easy question but I could not find an answer by searching the forum.

Greetings

Pietro

[Pietro7]

... and to complete the project the last two SubVI on which I am not sure if you need them.

[MelanieE]

Hi Pietro,

could you also mention, what hardware you use and version of LabVIEW?

Regards,

Melanie

[Pietro7]

Hello Melanie

Yes, I use a PXI-1036 Chassis with a PXI-4065 DMM and a PXI-5114 Scope Module. The installed Labview Version is 2012, 12.0.1f5 with Service Pack 1.

Regards,

Pietro

[MelanieE]

Hi Pietro,

the main problem in the code is, that you can not say, if the Scope or the DMM is started first and what is done when in your code. I would ask you to unite the Scope and the DMM code to one VI and

first initialize the Scope,

than the DMM,

configure the DMM to wait for the trigger signal on the scope,

start the DMM task,

start the Scope task

and then acquire the data.

Use the error line to sequence VIs.

There is a handshaking example for DMM and Switch in LabVIEW. Take a look into the example finder of LabVIEW to take a look at it.

Regards,

Melanie

[Pietro7]

Hi Melanie

Thanks a lot for your Answer. I will test it as soon as I get on the vehicle where the PXI System is measuring (until now it is just recording the data from the Scope channels). I'll keep you up to date!

Have a nice Weekend

Pietro

[Pietro7]

Hi Melanie and Forum Members

I tried to merge the Scope and DMM VI's to one VI and started the tasks in the order you told me. Unfortunately it is still not transmitting the trigger signal from the Scope to the DMM. The DMM starts the measurement without waiting for the trigger signal, so I get the value of the moment in which the Messung_v2.vi (Attachment) is called.

Do you have an other suggestion or idea what the fault could be?

Thanks for your support

Pietro

[Nathan-P]

In your code, you send the Digitizers "Start Trigger" using the niScope export triggers VI.  If you want the DMM to start taking measurements on the "Analog Edge Reference Trigger", then you need to change this to "Reference Trigger".  

Here is a diagram to explain the differences:

http://zone.ni.com/reference/en-XX/help/370592E-01/digitizers/5122_state_model/

Looking at this diagram, the start trigger occurs right before the first pre-trigger samples are acquired, or when niScope Initiate Acquisition is called.  This explains why it doesn't appear to be "waiting" for the same trigger the digitizer is.  The digitizer, after it starts, waits for a reference trigger, and the start trigger has already happened.

I hope this helps.

-Nathan