# LM331 for low frequency F to V

I am trying to use the LM331 IC for linearly converting a input frequency 0-150 Hz to 0-10V.

Based on data sheet formula for calculating the adjusting potentiometer I think a fixed 100Ohm with a 220 Ohm pot should be able to provide what I want.

But then formula is one thing but reality may be different since the input frequency is pretty low ?

Any tips ...?

The LM331 is a voltage to frequency convertor - the reverse of what you need.

Devices such as the LM2917 might be better, or use an Arduino to count or measure pulses.

pulseIn() does this quite well.

Allan

Ardubit: Based on data sheet formula for calculating the adjusting potentiometer I think a fixed 100Ohm with a 220 Ohm pot should be able to provide what I want.

You'd have to give us a clue what circuit you are using the LM331 in. Since it's basically RC timing/filtering, just mentioning an R value makes no sense on its own.

Yours, TonyWilk

“The LM331 is a voltage to frequency convertor - the reverse of what you need.”

Page 1 lists “Applications”:
V-to-F
F-to-V
remote sensor mon
tachs

See Fig. 19, “Precision Frequency to Voltage Converter”

TonyWilk:
You’d have to give us a clue what circuit you are using the LM331 in. Since it’s basically RC timing/filtering, just mentioning an R value makes no sense on its own.

Yours,
TonyWilk

Being a very popular IC like the 741 or 555 I thought a circuit is superfluous. Sorry. I am talking about the Rs resistor in the attached circuit…

Ardubit:
Being a very popular IC like the 741 or 555 I thought a circuit is superfluous

Lol.
Really, I did laugh at that !

You will have to read the datasheet and select values for Rt and Ct for the timer section to match the frequency range of your input (0…150Hz ?), then you can look at RS and RL and maybe select a different C on pin 1.

I do realise this means changing the circuit for this very popular IC. (but that example circuit is for 10kHz full scale)

Yours,
TonyWilk