How do I measure RPM from a gear tooth sensor.

[KNB1080p]

Hi

I have a NPN type gear tooth Hall Effect speed sensor that produces a pulse (voltage drops to zero then back to the pull up voltage value V) with every passing gear tooth.

I want to measure the speed of that rotating gear at a rate of at least a 100 Hz (meaning a 100 readings per second for monitoring purposes).

How do I perform this measurement? What hardware would I need? I currently have the USB 6002 with 1 built in counter but no hardware clock so I can’t perforce frequency measurements with it😭.

I know the formulae for RPM from pulses is:

I can I reliably get the Pulse frequency?

Regards.

[santo_13]

You can still reuse 6008 by capturing your pulse signal using analog input, do N sample read, read 100ms worth of samples every time, count the number of transitions in 100ms worth of captured analog signal, and convert to RPM.

Please note, this method has a bunch of downsides compared to native counter-based frequency measurement.

[altenbach]

What kind of software environment are you using? (LabVIEW? Something else?). Done right, reading the counter at somewhat regular intervals should be able to give you the desired measurements.

[KNB1080p]

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@santo_13 wrote:

You can still reuse 6008 by capturing your pulse signal using analog input, do N sample read, read 100ms worth of samples every time, count the number of transitions in 100ms worth of captured analog signal, and convert to RPM.

Please note, this method has a bunch of downsides compared to native counter-based frequency measurement.

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Thank you, will try that out. N samples with every read is what I didn’t think of doing.  

[KNB1080p]

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@altenbach wrote:

What kind of software environment are you using? (LabVIEW? Something else?). Done right, reading the counter at somewhat regular intervals should be able to give you the desired measurements.

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LabView 2021.

Yes I tried exploring that avenue but discovered that I only had 1 counter in the 6002 USB device and I need to measure +3 speed sensors.

So I made my own edge counter VI using the digital input with Boolean data and an interval of 100 ms but it would often skip counts and cause the rpm reading to drop with every few readings.

Will link the VI as soon as my Power is back.