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Analyzing rpm from a rotatory shaft

Good morning,


I am developing a vibration application, and I want to measure vibration and also angular velocity (in terms of rpm). I have some questions:


1- I have NI9232 and NI9234 cards (mounted on cDAQ9174 chassis). Exist any sensor which could be used with these cards in Flexlogger?

2- Additionally, I've got the NI9205, NI9219 and the NI9403 modules, if I could use any of them to measure the rpm.


Thank you very much.

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Message 1 of 9

Hi JJJ2020


There are a variety of IEPE vibration sensors available industry-wide that you could use to accomplish this with the 9232 and 9234. Some of them are listed here: https://www.ni.com/en-us/shop/select/vibration-sensor.


As far as the RPM measurement is concerned, depending on the type of sensor you have both the 9205 and the 9219 can help you accomplish this, while the 9403 being a digital input/output module cannot. If your RPM sensor is a voltage output one, the recommendation would be to go with the 9205 as it can support higher sample rates. The 9219 is slower but will let you use both a voltage and current output sensor. On the other hand, if your sensor is a quadrature encoder, you can use an NI counter input module to obtain the measurements.



Arunkumar Prabhashankar

Message 2 of 9

Hello Anunkumarp,


Thank you for your rapid response. Now I don't have a sensor, what do you recommend me? I need to do not only the measurement of rpm, but also to calculate phase of signals (as you know this is a part of vibration analysis, to evaluate problems such as misalignment, etc. Regards.

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Message 3 of 9

Hi JJJ2020


Could you clarify if you are looking for recommendations on what sensors to use or on how to set up the system?




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Message 4 of 9

Hello Arunkumar,


Both things. At this moment I have no sensor, but I want to accquire one and to define it on Flexlogger. My objective, as commented previously, is not only to measure rpm but also to analize phase difference between two accelerometers (it is very used on machinery vibration analysis).


Thank you very much.

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Message 5 of 9

I can't speak for the vibration, but I recently purchased the 9361 module and plan to use it to record RPM.  Based off my research this is going to be the simplest way and can be used with just about any RPM sensor out there.

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Message 6 of 9
Hello brethigh, Thank you for your response. How could you configure it in Flexlogger, to measure rpm? Is it possible to count in Flexlogger? ON the configuration of a sensor in Flexlogger there is an option called angular velocity. I understand that it is the way to measure rpm, but how it works? Thank you.
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Message 7 of 9

I don't physically have the module yet (I should have it in a few days) but it's my understanding from conversations and reading the manual for the NI-9361 module that it has an internal counter and time base that you can use to calculate the RPM by reading the pulses from your sensor.  Below is a link for the NI-9361 manual.



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Message 8 of 9

Hi JJJ2020

You can easily configure a channel on the 9361 in FlexLogger to be a frequency counter to measure RPM as can be seen on the screenshot below:


You have the option to select between a single ended configuration or a differential configuration for the terminals and what edge to count on. Alternatively you can use a quadrature encoder to achieve this.




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Message 9 of 9