SuperPID Tach Sensor Cable is NOT Shielded

Hey y’all, it’s been awhile since I stopped by. I’ve been on a few-month hiatus what with work getting chaotic. I just wanted to stop by and drop a quick note for anyone that might be looking for an answer to a question that led me down a rabbit’s hole to resolve.

The tach sensor cable, the one that’s sold with the SuperPID as a kit, is not shielded. Does it have a shield? Yes. But it is not shielded. Actually, the shield is used as a current carrying conductor. Electrical noise that’s induced into the shield conductor could potentially cause jitter in your tach signal, such as lost or extra pulses.

The solution I’m going with is to splice the kit sensor cable into a shielded 3 conductor cable. The kit sensor conductors being +, -, and SHLD, I’m connecting those each to one of the new cable’s conductors and connecting the new cable shield to actual earth ground at one end.

It’s probably not that big a deal, and I doubt it’d affect SuperPID operation. I’m just a stickler for this sort of thing. And it bugs me that a shielded cable is used unnecessarily- a shield used as DC Common is worse than just using an unshielded 3 conductor cable.

That happened to me on my homemade tach. Very frustrating when it works reliably off the machine but not when the machine is running. I switched cable with Cat6 because it is what I had on hand, and grounded the shield on one end. It worked. If you can get to the resistor used on the powerline to your IR sensor, you might try different values so the power is increased and the potential differential between pulses is increased. But I think you would also need to modify the code. I think it uses an Atmel processor.