PXIe-1065 chassis external synchronization

[lab0]

I'm using a PXIe-1065 chassis with an external 10 MHz reference, and this works well. However, I would like to synchronize the output to the 50 Hz power line frequency during a particular time window in my application.

My application involves a 40 second cycle during which the chassis controls multiple analog cards (5x NI-7333 cards). At some specific time during these 40 s, I want to synchronize the outputs of these cards with the 50 Hz power line frequency. This means that I want to stop all the analog outputs until the rising edge of the external 10 MHz reference signal and the 50 Hz power line signal coincide (for the comparison between the 10 MHz and the 50 Hz signals I have external hardware which works fine).

What I've tried is to interrupt the external reference clock until it synchronizes with the 50 Hz signal, my hope was that the outputs would stop until the cards see the external reference clock again. But as soon as I removed the external 10 MHz reference, the chassis internal 10 MHz clock kicks in which resumes the cycle instantly. I have gone through the PXIe-165 chassis user manual for a solution but I haven't found anything useful for this situation.

My questions are:

1. Is there a way to disable the internal 10 MHz clock?

2. If not, is there a TTL/digital input that I can send to the PXIe chassis to halt the outputs?

3. Has anyone implemented something similar or have ideas on how to implement it?

Thanks!

[VA.KI]

Hello,

I before go dipper I wold like to know what NI-7333 module we are speaking about?

I hadn't find any product under these name.

Why you don't use power line (of through coarse isolated channel) as trigger for sampling?

[lab0]

Hi VA.KI,

The modules we use are the NI-6733 modules, not NI-7333 (it was a typo).

The way we use these modules is we write the samples on the module's buffer at the beginning of the sequence and the clock keeps the execution of the samples on time. As timing is important (we care about ~100 microseconds in a ~40 s sequence), we don't write/read data to/from the modules during the execution.

In the past, we have done this kind of synchronization with the power line using PCIe modules directly connected to a computer where it was easy to remove the external clock (and therefore stop and start all the outputs). However, in principle, if we could configure an input channel as a trigger to stop the output of all the NI-6733 modules in the PXIe rack during an 'arbitrary' time in our sequence, this could work too. Is there any resource you can point to?

Thanks!

[VA.KI]

Hello lab0,

I've checked possible solutions.

Basically, NI-6733 doesn't have Stop Trigger. This is not good. In general, DAQmx doesn't have Stop Trigger functionality.

Using chassis also is not possible. It will automatically synchronize.

One solution I see is to get synchronized with the power line at the beginning and count time accordingly.

40*50 = 2000

We can use the PFI ports of the module and make some galvanically isolated converter which will give pulses each time when power line sine wave crosses zero. Module has internal counters.

So, after counting 2000 outputs will be stoped, this will be programmatic "Stop Trigger".

We can check and see if it fits into our expectations.