I see that the Spartan Lite V3 requires two seperate earth connections. The installation instructions state one must be earthed on the engine. Is that really necessary given that the engine is earthed to the body through the mounts (and in my case an engine earth strap)? What is the reason that two seperate earth points are required? Could the earth wires be earthed to the body just a few cm’s (an inch) apart?
The black wire is the electronics ground, it carries ~100ma of current, you want to ground this close to where the device connected to the analog output is grounded to minimize ground offsets.
The white wire is the sensor heater ground, it carries 1-3 Amps of current, the quality of this connection does not matter much, you can ground it anywhere you want. Ideally you ground this far from where the black wire is grounded so the heater ground currents do not cause ground offset.
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That’s really helpful, thank you. That makes a bit more sense and helps with the routing of the wires etc.
Just a thought, instead of earthing to the engine, could the heater earth wire be run to the negative terminal of the battery?
battery is fine for ground