Low Freq Tachometer

[fode]

I'm designing a tachometer to measure a shafts rpm, using a freq-volt converter. the rpm can vary from 0-500. all the chips i have looked at have bottom end 10kHz pickup. can anyone suggest an alternative chip or method i could use?

these are the chips i have already looked at
AD537JH
AD650JH
AD602AQ
AD654JN
ADVFC32KN
LM231N
LM2917N-8
LM331N
MM74C922N
TC9400CPD
TC9401CPD
TC9402CPD
VFC32KP
VFC320BP

thanks

 

[john1]

Hi fode,

You could try an old mechanical speedometer.
That sounds like about the sort of rev range.

Quite easy to find, very reliable, no supply needed.

Regards, John

 

[Joel Rainville]

I'm designing a tachometer to measure a shafts rpm, using a freq-volt converter. the rpm can vary from 0-500. all the chips i have looked at have bottom end 10kHz pickup. can anyone suggest an alternative chip or method i could use?

these are the chips i have already looked at
AD537JH
AD650JH
AD602AQ
AD654JN
ADVFC32KN
LM231N
LM2917N-8
LM331N
MM74C922N
TC9400CPD
TC9401CPD
TC9402CPD
VFC32KP
VFC320BP

thanks

A simple magnet/reed switch perhaps? Just like a bicycle speedometer?...

 

[Styx]

yup if you dont need accurate position measurement then just count pulses

 

[williB]

yeah., it depends on how you want to register a shaft rotation??
your best options are optical or magnetic
using a hall effect switch (and a magnet )produces a nice clean signal to count..

 

[jbeng]

Don't forget about using a gear on the shaft with a magnetic coil-type sensor to sense the teeth on the gear. That way you get numerous pulses per revolution, instead of just a couple. Although, like williB said, a hall effect setup does give a nice clean signal ... but with a little bit of signal conditioning, the coil setup will too.
Here's a link to a thread where we discussed this previously ...
https://www.electro-tech-online.com/threads/how-to-measure-current-in-pic-pic-as-an-ammeter.10097/
Jeff

 

[Nigel Goodwin]

I'm designing a tachometer to measure a shafts rpm, using a freq-volt converter. the rpm can vary from 0-500. all the chips i have looked at have bottom end 10kHz pickup. can anyone suggest an alternative chip or method i could use?

A 555 timer in monostable mode would do the job, they are commonly used as rev counters.