[Tom Bottiglieri]

You could build a test kit with the EDU-RC. Wire up green, yellow, and red LEDs in a line, and another special red "warning" LED. When the encoder is moved clockwise (forward) have the green light up. When at rest, have yellow light up. When revolving CCW, have red for reverse come up. If there is no signal, or an erratic signal have the warning LED come on. This may be an easy plug and play way to check quickly for dead encoders.

If you like this idea, or something similar, but are short staffed in the programming department, send me a PM and I could probably whip something up for you.