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Shaft Speed & Vibration Phase Measnt. from Trigger?

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Shaft Speed & Vibration Phase Measnt. from Trigger?

Postby musicman » Thu Sep 01, 2016 8:32 pm

I intend to purchase a 4ch scope (2405A) which would be used to measure vibration from rotating machinery. My question is regarding triggering the data collection. I need to make a decision regarding how I measure the speed of a rotating shaft and also obtain a phase relationship between the measured vibrations.

I would plan to use channels 2,3 & 4 to measure vibration using accelerometers. The decision I have to make is regarding what signal I can use in CH 1 to trigger the data collection. I can provide a once-per-revolution pulse signal using a displacement probe close to a shaft protrusion such as a screw. I assume this would work but the problem is the cost of this setup is high for a 'hobby'. An alternative is to use an inductive switch sensor which apparently produces a TTL signal.

My first question is very specific and is - "could the TTL signal be used to obtain shaft speed and to provide a phase reference between the vibration signals?"

My second question is more general and is - "how easy would it be to obtain a shaft speed measurement and relative phase measurement between the signals in channels 2, 3 & 4 if a suitable trigger signal could be supplied to channel 1?"
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Re: Shaft Speed & Vibration Phase Measnt. from Trigger?

Postby Martyn » Fri Sep 16, 2016 10:15 am

If you download the software and run it in demo mode you can see the basic features.

In the bottom right of the display are the phase rulers, green circle, which can be pulled onto the trace to indicate the start and end of a full cycle. In the bottom left are the time rulers, white square, which can be pulled on to the trace to see the phase relationship between any point on the screen and the phase rulers.

You can set set up a maths channel to calculate the frequency of a signal and convert this into revolutions per second/minute etc drawing the resultant trace on the screen.

If you require assistance in setting this up please email support@picotech.com
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