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How do I get RMS values of AC voltages in Flexlogger?

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Running flexlogger with a Cdaq with high voltage and current modules.  Wondering if there is any features in flexlogger to display rms values?

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Hi cmoffitt,


I've been looking through a few different methods to try displaying RMS values for channels, and so far I haven't been able to find anything.


I tried calculated channels to see if I could only display a maximum, but it looks like calculated channels currently only support arithmetic and trigonometric functions. I also haven't seen anything in the physical channel setup that would allow you to configure RMS values.


I'll check with some other colleagues to see if I can find a more definitive answer, but so far I haven't been able to find a way to display RMS values. If anyone else knows otherwise, please post!

Andy F.
Applications Engineering
National Instruments
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Support for statistics calculations like RMS, min, max, average, and so on, is on our feature backlog but are not yet in the product.


Could you provide some details about your application (what you're testing, the hardware you're using, et cetera)? This information would be helpful to us as we prioritize future feature efforts.

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Devices that are being tested are commercial freezers and grills in all power configurations for regulatory approval (UL, IEC).  Voltage set points are set and maintained throughout these test phases via auto transformer.  These test are conducted for hours while the appliance is operated by the technician.  Due to the industrial infrastructure power fluctuates through out testing and must be adjusted by the technician.  Power fluctuation effect the thermal stability of components and can increase the length of the test.  RMS values of current are also important through out testing, so we have an indication of how components are behaving.


Not having these values during testing but after (post processing) could result in having to rerun the test again.


So we are reviewing FlexLogger in our lab.  We currently have two CDAQ chassis with two copies of PVI Chameleon data acquisition software (Which does give us RMS measurements).  I am in the process of releasing these test stands to the lab technicians and was undecided which Daq software to implement (Chameleon or FlexLogger).  I would prefer to go with FlexLogger because our corporation is in the volume license program with NI and would be the best option long term for us.  Future DAQ hardware is going to be CDAQ to replace our Agilent 34970A inventory (QTY: 16 which we currently have RMS capabilities via Ohio Semitronic transducers) throughout the coming years.

Equipment currently being used with FlexLogger.



NI 9220

NI 9214

NI 9227

NI 9246

NI 9247

NI 9244



Message 4 of 6
Accepted by topic author cmoffitt
05-09-2018 11:13 AM

Thanks cmoffitt. I really appreciate you taking the time to provide some additional context. I will make sure this information gets in front of the team. I know that you also have a service request open, so we can work with you via that support ticket to provide you with a recommendation on how to proceed.

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Accepted by topic author cmoffitt
03-13-2019 09:05 AM

Hi cmoffitt. I wanted to let you know that FlexLogger 2019 R1 just released with support for RMS and Mean channels. You can create these channels, map them to the source channel, and set the block size, which controls the amount of data in seconds used for the calculation. This allows you to balance accuracy, latency and update rate. These channels are available to visualize on screens, and they get logged to file like any other channel.


You can download the latest software from ni.com/flexlogger, or directly from NI Package Manager (provided you have the NI Package Manager 18.5 or later).



Jarrod S.
National Instruments
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