DC tachometer 1

[TheApprentice]

Hello All:
We are currently using a Tachometer (1000RPM = 100VDC) as a feedback signal into the DC drive package.
I was wondering if anyone has seen an application where people tab into this tach signal and feed
an undervoltage DC relay where it will tell us if the motor is up to speed.
There is an existing Zero Speed Switch, but the unit has failed for a long time, and we are looking for an alternative.
Thanks
George

 

[nbucska]

What is the nominal RPM and at "zero speed" ?

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

 

[aolalde]

I think your only problem should be the burden that the relay will impose to the tachometer. If the load is to large the voltage drop will generate a wrong reference.

 

[Skogsgurra]

Like aolalde says. Find an electronic relay with high enough input impedance (anything from 100 kohms and above will work with a standard DC tach).