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Ground and Earth

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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You often hear people referencing ground and earth, with one side of the discussion saying that they are the same and the other saying they are fundamentally different. Can you clarify this please?

Hello yes this is confusing until it is explained

One of the major difference between the grounding and the earthing is that in grounding, the current carrying part is connected to the ground whereas in earthing the non-current carrying parts is connected to ground.

this gets even more confusing as most people just say whichever word comes to mind and mix up their earth and grounds

in the automotive world, we ground everything we have different grounds one is sensor ground which is a specific wire from a sensor to the ecu this can be shared between many senors like tps oil pressure fuel pressure and so on. then the sensor ground wiring is connected internally to the ecu ground which a wire from the ecu goes out and is bolted to the head or block or both. this can sometimes be called earthing wires, i may have just confused you more but i hope not

Very pertinent point!

'Old School' vehicles with carbies and Kettering ignition (points based) had simple electrical systems where minor differences of voltages across different components had negligible importance - except, maybe, in radio interference noise. So it was simpler, and cheaper, to just use a sigle wire and use the frame/body fot the other half of the circuit.

However, modern vehicles use electronics for almost everything and for them minor variations in voltage across devices and sensors/senders can be critical - milli- (thousandth) and even micro- (millionth) volt and amp variations are used by the electronic's logic, and if they were simply connected to the vehicle's chassis/body as the earth return, there can be small variations between different points of the chassis/frame voltage potentials, which can cause problems. Check out "ground loops" and you'll see why there is so much emphasis put on common ground (return) points for components on the same devices.

It doesn't help that many terms, and thought processes, derive from the older electrical practices, where - as Ross said - it was common practice to connect the neutral/ground to a physical earth which would be a metal stake driven into the ground, and sometimes these different electrical paths were used interchangeably. The reason for this 'earthing' of electrical devices was because it was other possible for a fault to make a metal part 'live' and for someone touching it to receive a shock by providing a path to ground - if the metal parts were connected to ground/earth, there would be an internal short (hopefully just blowing a fuse and not burning down the house) with that ground path reducing the chance of a shock or electrocution.

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