simple in line frequency counter? Need to measure 48hz variable resistor

[Djwerk]

Confused.

Been searching all day. Is there a simple way to measure if I've correctly adjusted a variable resistor from 50hz to 48hz?

Below is the email to me from Russia, explaining how to adjust the variable resistor.

This is variable resistor adjust a speed of motor.

But, you need frequency measuring device for check a value of speed.

You can connect measuring device to Pilot signal socket .

50 hz signal = 25 fps.

48 Hz signal = 24 fps.

Other idea, you can take frequency from resistor R6 on PCb.

25 fps = 500 Hz

24 fps = 480 Hz.

[Zachmx]

Hi Djwerk,

This question might be better answered in the specific hardware forums if you are using an NI Data Acquisition Device or in the LabVIEW forums if this is strictly a software question. Could you give me some more information about the harware you are using/want to use to make this measurement?

As a general solution, you could use a multimeter to simply measure the resistance as you change it. If you are applying a known current, you could measure the voltage across the resistor and calculate the resistance. If you want to directly measure the frequency, you could input an analog voltage signal into a DAQ card and use a Fast Fourier Transform in software to calculate the frequency of the signal.

[Djwerk]

Thanks.

The Russian Tech, said certain multimeters test frequency. It's for a motion picture camera motor and 50hz equals 25 frames per second operation which is standard for Europe and 48hz equals 24 frames per second which is the standard for US. It needs to be adjusted to 48hz so I need a multimeter that will tell me that it's at 48hz. I don't know which multimeter will do that.

[Zachmx]

Hi Djwerk,

Are you using any National Instruments hardware or software with this system? Many of the NI devices that support analog voltage input could be used with LabVIEW to find the frequency of your signal. A quick Google search should point you in the right direction for frequency multimeters. Also, I linked a basic DMM below for reference.

http://www.amazon.com/Velleman-Digital-Multimeter-Temperature-Capacitance-Frequency/dp/B0006HJQV6