Measuring VFD frequency with 7i76e

Yes it is, in several ways if you have encoder inputs.
But I doubt it does output the frequency, although that is easy to implement.
I also think that you can use a normal input on the mesa board, but that would have to be confirmed by PCW.
Usually they do 400Hz so maybe that would be possible to count from a normal input, or you can put the 7i76 in mode 2 and have another 2 encoder inputs that are usually used for MPG encoders. That would still leave the existing spindle encoder input for what it is intended.

JetForMe wrote:

There's an encoder input on the 7i76e, but this isn't really that. Is there a way to use one of the inputs to measure frequency?

The encoders can count a single channel in "counter mode", this is true of the Mesa mpg and real encoders and the software encoder module.
For 400Hz the software counter would be fine, with 1kHz sampling rate.

at 800Hz I would probably suggest using a hardware rather than software counter.

There are spindles that can do 60000 RPM, seen and worked with two types of them, small but they chew through titanium and zirconium nicely. They do require 1000 Hz to work.