This is what I started with - DS1054Z math to show the difference of two signals:
With the differential probe, I can get a better signal representation and get one input channel back.
Here's a sample screenshot that actually shows what the probe does:
- supply voltage to motor: 5V, duty cycle about 60%
- Ch1: 3-state PWM input to motor phase A
- Ch2: bemf from phase A, through a 10k/2k2 voltage divider
- Ch3: virtual center (all phase feedback signal tied to a common node through 2k2 resistors)
- Ch4: Ch2-Ch3, using the diff probe
It has been a very pleasant journey into the analog world for me. Thanks Bud!