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golubovski
Posts: 210
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Proper IEPE Source Turn-OFF

Hello,

 

I plan to use 4 chassis in a synchronous DAQ - 1x PXI and 3x cDAQ configured on individual-channel basis. Some of them reading Voltage (conditioned transducers) and some of them ACC (IEPE accelerometers). Before the main DAQ.VI I configure the 4 tasks (1 per chassis) and have tor ead starting offsets of all channels in use. This is the "Save Nulls.VI", having a button to allow a 60 sec settling ICP time before the acquisition sessions. The ACC channels are for now on the PXI chassis (PXI-4472 modules). Since the PXI chassis IS NEVER SWITCHED OFF I know that after the 1st acquisition all IEPE channels will remain ON forever.

 

So I need a VI to turn the IEPE currents every day before we leave. I have read of more solutions and decided for a Voltage dummy reading of a single sample of all channels. Attached is its diagram.

 

Is this a correct solution?

 

Thanks in advance,

Member
KatieC
Posts: 103
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Re: Proper IEPE Source Turn-OFF

golubovski, 

 

I was taking a look at this article. One paragraph seemed particularly relevant:

 

"Enabling IEPE excitation closes a relay on the DSA device. Once turned on, either by using a microphone channel or by using a property node, IEPE excitation will stay on for that channel until explicitly turned off. The IEPE excitation will even persist after you clear your DAQmx task. To turn off the excitation, use a property node with an excitation value of 0."

 

I would try using the property node instead. 

 

Katie

 

Katie Collette
Product Marketing
National Instruments
Active Participant
golubovski
Posts: 210
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Re: Proper IEPE Source Turn-OFF

Katie,

 

Thank you for responding! So you suggest I rebuild the AI tasks and lower the IEPE currents down to 0, instead of a dummy voltage read?

 

Thanks in advance,

Member
KatieC
Posts: 103
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Re: Proper IEPE Source Turn-OFF

That is correct! :smileyhappy:

 

Katie

 

 

Katie Collette
Product Marketing
National Instruments
Active Participant
golubovski
Posts: 210
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Re: Proper IEPE Source Turn-OFF

Katie,

 

I have attached a working VI - is it the correct way?

 

Thanks in advance,

Member
KatieC
Posts: 103
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Re: Proper IEPE Source Turn-OFF

That looks great!

 

Katie

Katie Collette
Product Marketing
National Instruments
Active Participant
Brad_K
Posts: 624
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Re: Proper IEPE Source Turn-OFF

Hi golubovski,

 

DAQmx doesn't program the hardware until you commit or start the task. Add a DAQmx Control Task VI with the input set to "Commit" between the property node and the DAQmx Clear Task VI.

 

Brad

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Brad Keryan
NI R&D
Active Participant
golubovski
Posts: 210
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Re: Proper IEPE Source Turn-OFF

Thank you Brad!