Frequency Measurement of a voltage signal

soxso2011 · 2016-01-12 07:18:47

Please suggest a method to measure frequency of input signal, which block will be used and how to integrate with raspberry pi.

jaroslav_sobota · 2016-01-12 11:33:01

Please specify the amplitude and frequency ranges of the voltage signal. How often does the frequency change? What is the source of the signal? If you have some screenshot or sample data, upload it here.

soxso2011 · 2016-01-12 13:42:35

Amplitude Range 0 to 3.5 V Square wave
Frequency range 2Hz to 250 Hz
This is the output of Flame scanner used for flame detection in Thermal Boilers.

jaroslav_sobota · 2016-01-14 18:32:03

Find the enclosed example on processing the pulses. It consists of one quick task for counting the pulses (sampling rate 2ms = 500Hz) and another task at sampling rate of 100ms for converting the counter value to frequency and providing real-time data trend. It works nice on my Raspberry Pi2.

The main idea is counting pulses and comparing it to a delayed signal. The more the signal is delayed, the smoother values you get. On the other hand, the signals get delayed... Set the delay to fit your application.

Remember to use e.g. voltage divider, the GPIOs of the Raspberry Pi can handle only 3.3V!

Download all 3 files and put them in one folder. The freq_exec.mdl file is the project main file.

soxso2011 · 2016-03-01 07:50:13

It works very well !
Thanks

jaroslav_sobota · 2016-03-01 08:34:53

Glad I could help. Thanks for your feedback!

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#1 2016-01-12 07:18:47