PXIe-4080 Simultaneous Waveform Acquisition

[JHall92]

Hi everyone!

I am attempting to use a PXIe-1073 chassis with 2 PXIe-4080 DMM/Digitizer cards to acquire voltage/current waveforms of a 60Hz signal then perform waveform analysis to obtain apparent power, real/reactive power, and power factor.

My issue is that I believe I am not acquiring both waveforms simultaneously.

I've attached a quick sample VI of what I have done. In the VI, I initialize both DMMs then configure one for voltage waveform acquisition and the other for current waveform acquisition. Both DMMs are set to a sampling rate of 20kS/s with 1000 samples.

After this I merge the errors and wire the output error into 2 read waveform VIs. This was my way of reading data "simultaneously".

Is there a way to configure both DMMs to begin acquisition at the same time? I've looked through the NI DMM palette and explored the property node as well, but nothing sticks out to me.

Any help is greatly appreciated.

Best regards,

Jeremy

[ZYOng · Accepted solution]

You need to configure triggers, preferably hardware triggers.

How Can I Trigger and Synchronize NI PXI(e) DMM Cards Using Software?

[JHall92]

Hi ZYOng,

Yes, I've looking into triggering this morning. I came across the link you sent earlier and was looking into the second example using the NI DMM Configure Measure Complete Dest VI.

To me, this example looks like the 2nd measurement (using TTL0 as trigger) won't take place until the 1st measurement is complete. Do you know if this is correct?

I actually have 3 PXIe-4080 devices. 1 which is not being used during this portion of measurements. So if the case above is true, I could just use the extra PXIe-4080 as the master, have it take a dummy measurement, which will trigger TTL0 for the other 2 DMMs to acquire at the same time.

[JHall92]

After looking into this matter a little more, I am beginning to wonder if I can trigger the DMMs by configuring both triggers to TTL0. I can then assert (PXI: Reserve?) TTL0 using VISA Assert Trigger VI with the PXI backplane resource name, wait until acquisition is complete, and fetch the waveforms. I would then de-assert (PXI: Unreserve?) using the VISA Assert Trigger VI.

Is this a reasonable approach?

Best regards,

Jeremy

[ZYOng]

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@JHall92 wrote:

Yes, I've looking into triggering this morning. I came across the link you sent earlier and was looking into the second example using the NI DMM Configure Measure Complete Dest VI.

To me, this example looks like the 2nd measurement (using TTL0 as trigger) won't take place until the 1st measurement is complete. Do you know if this is correct?

---

Your understanding is not correct.

When we call DMM Configure Trigger VI, we simply ask the device to get ready to process triggers. No acquisition has been started yet. The sending and receiving of triggers only happen when we call DMM Start VI.

In the example, the slave device (that has TTL0 trigger configured) is first started, to arm the device to wait for upcoming trigger. Then we start the master device by sending it a pre-configured software trigger, which will then be routed to TTL0 automatically.

[JHall92]

Thank you for the clarification on that. For some reason the naming and help context of "Configure Meas Complete Dest" threw me off.

Please disregard the post I made after this regarding "Assert Trigger".

Also as another reference this link provided me an explanation of Master-Slave Synchronization:

Synchronization Explained - NI

Best regards,

Jeremy