Shielded wiring for sensors

71dsp
Posts: 19
Joined: Sat Apr 19, 2008 4:07 pm

Shielded wiring for sensors

Postby 71dsp » Thu Nov 12, 2009 10:39 pm

When wiring up a 3 wire sensor (reference voltage, signal ground, and sensor signal) and using shielded wire, is it best to have all 3 wires in a single shield, only the signal wire shielded, only the reference voltage and signal shielded, or some other combination?

Would the same apply to two wire sensors?
Billy
98 Prelude - #27 NASA TX PT

osborni
Posts: 497
Joined: Fri Dec 07, 2007 9:08 pm
Location: USA, Michigan

Postby osborni » Fri Nov 13, 2009 1:25 pm

Sensors draw so little current that there typically isn't an issue with shielding all three wires.

Just make sure that you ground the shield on one end only.
BMW 2000 M Coupe

71dsp
Posts: 19
Joined: Sat Apr 19, 2008 4:07 pm

Postby 71dsp » Fri Nov 13, 2009 4:53 pm

Thanks. A few other questions, if you don't mind.

Currently I'm using 3 datalogged sensors for the engine: water temp, oil temp, and oil pressure. I may add a fuel pressure sensor as well, and eventually I want to add suspension pots. All of the wiring will be run together to a bulkhead connector on the firewall. Shound I ground the shields at the firewall connector or at the opposite ends, at the sensors?

If shielded wire is used on both sides of the connector, should the shields be connected by using a pin in the connector, or should they be grounded separately?

I assume 22 Gauge MS27500 will be more than sufficient, correct?

Also, during this process, I plan to rewire my current engine harness, as I want to remove quite a few unnecessary items, and I have access to all the OEM pins, so I can completely build the harness from scratch. The OEM EFI system uses two wire (VR, most likely?) sensors on the crank and cams. The OEM setup shields only the sensor wire, not the ground. The sensors do not share a common ground, as each has its own ground at the ECU (same for the sensor signal, obviously). Is it ok to use a two wire shielded cable, or should I wire up exactly like OEM? I figure the OEM setup is best, but I wasn't sure if I could get a better "quality" signal by shielding both the signal and the ground (or perhaps if both are contained in the same shield, the signal will be degraded?).

Same question applies to the ABS sensors as they are two wire sensors.

Thanks a ton! I can't believe how little information there is on the internet regarding these questions.
Billy
98 Prelude - #27 NASA TX PT


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