reset timing on PXI-6225

[DeOdderKeith]

I have a number of PXI-6225's in a PXI Chassis.

They are all configured and start collecting data at approx 1-sample per msec.

However, at one point, I would like to change a channel's data collection to 250kSamples per sec, collect some data,

and then change it back to the 1-sample per sec.

Is this possible?

What would be the easiest way? Do I have to stop the 6225 completely, then setup the channel, then collect the data, then stop the channel and re-setup the device to resume collecting?

DOK

[John_P1]

Hi DOK,

Do you need to sample at 1 kHz or at 1 Hz (you mentioned both "1-sample per msec" and "1-sample per sec").  Also, is there an external signal that is going to trigger the switch from 1 Hz to 1 kHz, or is the switch software-defined?

If software-defined, you might consider generating a sample clock signal from a counter and updating the rate on the fly.  You also might try something similar using the Analog Output sample clock instead.

There are also other solutions for what you need to do if you need a hardware-defined switch.  This would likely be more complex and might need the use of change detection;  I can elaborate more on this if you provide more specific requirements, but hopefully this at least gives you a good starting point.

-John 

[DeOdderKeith]

Hey John:

Sorry to be misleading.

I start off with the 6225 running at 1kHz collecting 100 samples every 100 msec. I'm collecting from a number of channels, usually between 1-12 channels. At some point I need to stop this, and collect samples at 250kHz (the fastest possible), but from experimentation I notice that I can only collect 1-ch at a time at this rate.

So I am guessing I need to stop all the channels, reset the device and configure to collect from 1-ch at the High Speed. Then when I'm done, re-configure the device to collect all 1-12 ch's at 1kHz, collecting 100 samples every 100 msec, like before, and continue?

[Steve_B]

Hi DOK,

You are correct, the PXI-6225 can sample up to 250kS/s for 1 channel and 250kS/s aggregate sampling rate for more than 1 channel. If you want to switch between 250kS/s and 1kS/s and change the number of channels in the acquisition, then you will not to stop and restart the task with the different configuration. This will result in a down time on the order of a few milliseconds to reconfigure the hardware.

Steve