Tachometer display when connected to a PWM controller

Hi, I am looking at doing a small project with work. They would like a Tachometer display when a Pot is turned connected to a M171PWM contoller (M171 PWM Power control 9 - 28 V/DC, max. 10 A)
Basically, when the pot is turned, it will range from 700RPM (low idle) to 2300RPM (high idle).

What would I require to achieve this ? Thanks so much in advance. Ian.

Tap off the PWM through an Optocoupler and send the tapped signal to a MCU that will count the pulses and display the frequency on a display.