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Wiring Fundamentals: Analogue Voltage

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Analogue Voltage

01.45

00:00 - Sensors that output an analog voltage are possibly the most common you will come across, as they are on almost every EFI system with an aftermarket ECU in the form of throttle position and manifold pressure sensors.
00:12 The majority of additional data sensors you find will also fall into this category.
00:17 Fuel and oil pressure, pedal position, and suspension displacement to name just a few.
00:21 Analog voltage sensors will typically have three wires, sensor supply, sensor ground, and sensor signal.
00:28 It's critical that these sensors are powered by regulated sensor supply and grounded to the sensor ground of the ECU.
00:35 Their output is proportional to their supply voltage and ground.
00:38 For this reason the ECU needs to be in control of the supply voltage and they need to share the same ground as the ECU for us to be able to rely on their signal.
00:47 However as with everything in the automotive world, there are some exceptions to this.
00:52 You will also come across external sensor interfaces that output a voltage signal to the ECU but are powered by the 12 volt charging system of the vehicle.
01:01 Wideband oxygen sensors and exhaust temperature thermocouples generate signals that most ECUs cannot read directly, and require interface boxes to convert these signals into an analog voltage the ECU can accept.
01:14 It's common for these interface boxes to be powered by the 12 volt power system of the car and grounded to the EFI system power ground.
01:22 The voltage they output will be referenced to this power ground point and not the sensor ground level within the ECU.