Pololu G2 current sense output for Spindle load meter?

Hello,

i am currently using a Pololu G2 PWM driver to control my Servos and it has a current sense output (approx. 20 millivolts per amp) could i use my 7i73 analog input for this? what resolution do the 7i73 analog inputs have? If not what would be suitable/easy to implement and fast enough? I already use 2 of the 4 analog inputs for spindle and feed override using Potentiometers but the voltage coming out of the Pololu driver will never be 3,3v (that would be 165 amps, maximum is 21 amps continuous/current chopping @50amps). I want to implement a Spindle Load meter and maybe also axis load meters as well. (if there is a board out there compatible with Mesa hardware which has a minimum of 7 analog inputs please let me know)

thanks

It sounds like a direct signal from the current sense resistor
(too small signal), plus theres probably quite a bit of common mode
noise (since the PWM power ground = current sense common)
and enough ground bumping that you might damage the 7I73
analog inputs if directly connected.

One solution is to add a differential amplifier (OpAmp+ 4 resistors) with a gain of 10 or so you can reject the common mode noise, and amplify the full scale signal, and protect the 7I73 analog inputs from voltages < -.6 and > +5V

i have a Arduino Mega 2560 laying around, would this work? It has 16 analog in pins. I once had a program on the Arduino which sent signals to linuxcnc via USB so i guess sending float values to Linuxcnc should be doable as well?

so basically you connect the current sensing output from the Pololu driver into the input from the opamp and the output of the opamp into the analogin from the Mesa card?

thanks

Quite sure it has to be a rail to rail opamp.

what about the Ti OPA 2350? www.ti.com/lit/ds/symlink/opa2350.pdf