This video should provide enough guidance to understand the PWM signal on the Mach3 USB controller:
The PWM signal is provided by the AVI terminal, and the 10V terminal is an input and provides the reference for the top voltage for the PWM signal. The ACM is the analog common (analog ground)
Additional Information:
Hello again, thank you for your help. Finally I was able to measure voltage between AVI and ACM, but another issue occurred.
In Mach3 I am able to control spindle speed - voltage output only from 50% to 100% in other words from 0% to 49,9% the voltage output is 0V, when the percetage exceed 50% I see immideately 5,2 V as an output which is linerly increasing up to 10V. I also tried to chage input voltage from 10 to 5V, but wirh the same effect, from 0%-49,9% 0V and from 50% I see cca 2,6V which then linearly increasing up to 5V.
It seems that my board is operating only in range of 5V. Thank you in advance for any advise. BR Vaclav
Click the link to add information to this solution:
[575] Hello, I'm wondering if you can provide advice how to wire this USB board where for spindle I would like to use chinese servo motor and driver (TD3) - speed control mode. Especially how to connect - AVI, ACM and 10V (24V is clear). I am still not sure how to power on and off spindle itself. Thank you in advance. Vaclav