frequency measuring

ertansuluagac · Joined: 13 Jul 2017 Posts: 135 Location: IZMIR

Hello there,
1- I want to something ask. I want to measure the frequency with the incoming pulse.
2- Can I measure frequency directly from an inside ?
I using microprocessor dsPIC33EP256MC502. I using crystal 16mhz with clock 120mhz.
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Es

gaugeguy · Joined: 05 Apr 2011 Posts: 303

What is the frequency range of the signal you want to measure?
Will the signal be conditioned to a square wave input 0-VDD?

ertansuluagac · Joined: 13 Jul 2017 Posts: 135 Location: IZMIR

I do not know that. It is flow meter. I will calculate according to the incoming pulse. I only get a pulse from a Vout. This is constantly changing. So I can't say anything clear.
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Es

temtronic · Posted: Wed Jun 26, 2019 8:57 am

'Flow meters' tend to be low frequency devices though the mfr of it will have charts/data of flow rate vs frequency (PPS). Even the cheap ones from China have data on the website. There will be a relationship of volume of water to pulse (1 revolution) so you could create an ISR to count pulses and calculate both flow and volume.

Jay

Mike Walne · Joined: 19 Feb 2004 Posts: 1785 Location: Boston Spa UK

Have a look at your input pulse with a 'scope. If it's not close to being a 0 to Vdd square wave then you will need to process it.

There are two general ways of measuring frequency:-

1) Count the No. of pulses in a fixed time (say 1s).
2) Measure the period of one (or several) pulse(s) and convert.

For a flow meter you will probably use the 2nd method.

Mike