Measuring Multiple channels at a time

[venkatgill]

Hello All,

I am new to Labview trying to measure voltages and currents from a synchronous generators using LabView7.1 abd PCI-MIO-16E-4. I want to measure all the three phase voltages all at a time so that I can see the phase difference between them. I modified an example for my purpose but it can measure only one channel at a time.

Anyone please look into my file and modify it for multiple channels.

Thanks in advance

Venkatgill

[Dennis_Knutson]

To measure multiple channels, change your physical channel control. For channels 0 thru 2, your control would be Dev1/ai0:2. When you click on the arrow on the right side of the physical channel control, you can select Browse and then highlight multiple channels by holding down the shift key. The control will then be automatically populated with the channel list. You should also not that your board does not support simultaneous sampling so the phase measurement is going to be off by the inter-channel delay.

[venkatgill]

Hello Dennis,

Thanks for the info. So, I cannot measure all the three phase voltages at a time with my DAQ Card right? But I see that many used the same card for simultaneous measurements. May be there is some other method to do this. Thanks once again

Venkatgill

[Dennis_Knutson]

Let me explain. Your board has a single A/D. There is a mux that rapidly switches between channels. It will take a sample from channel 0, then channel 1, then channel 2, and then start all over again. It will repeat until the total number of samples that you requested have been taken. The switching is very fast - on the order of usec, so you can take the 3 measurements but it is not truly simultaneous. Depending on the frequency and the accuracy of the phase difference you're looking for, this may not make a difference. You can also get the inter-channel delay and compensate for it.

[venkatgill]

Hello Dennis,

This time I got the concept from your message. It doesnt matter if there is some inter-channel delay. But the problem is I could not select 2 or more channels by holding the shift key. It is simply moving to another channel istead of holding to the previous one also. Is there any other way of selecting more channels at a time. I tried also with creating a task with 3 channels and made it global, but it didnt work. Please let me know if it is possible.

Thanks

[venkatgill]

Hello Dennis,

Sorry abt that. Thanks for your help and I got selected multiple channels