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Oxygen sensor 

An oxygen sensor (or lambda sensor, where lambda refers to air-fuel equivalence ratio, usually denoted by λ) is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analyzed. The most common application is to measure the exhaust-gas concentration of oxygen for internal combustion engines in automobiles and other vehicles in order to calculate and, if required, dynamically adjust the air-fuel ratio so that catalytic converters can work optimally, and also determine whether the converter is performing properly or not


The narrowband oxygen sensor is generally based on a solid-state electrochemical fuel cell. It consists of two electrodes that provide a certain output voltage depending on the amount of oxygen in the exhaust system relative to that in the atmosphere.

Coolant temperature sensor

An engine coolant temperature sensor or ECT measures the temperature of the liquid coolant. A typical engine cooling temperature sensor is a Negative Temperature Coefficient (NTC) thermistor, which means its electrical resistance decreases when the temperature increases. The tip of the ECT sensor protrudes into one of the cooling system passages and is immersed in coolant. Many cars have more than one coolant temperature sensor. In most cars, the primary ECT sensor (ECT sensor 1) is installed near the thermostat in the cylinder head or block or on the thermostat housing. A second coolant temperature sensor could be installed in another part of the engine, or in the radiator. Some cars use a cylinder head temperature or CHT sensor instead of, or in addition to the ECT sensor. The CHT sensor (see the photo) works the same way, but it measures the temperature of the cylinder head metal and is not immersed in coolant. This allows the CHT sensor to measure the temperature of the engine correctly even with the loss of coolant. This can help prevent overheating.

Wheel Speed Sensor

A wheel speed sensor or vehicle speed sensor (VSS) is a type of tachometer. It is used for reading the speed of a vehicle's wheel rotation. The most common wheel speed sensor system consists of a ferromagnetic toothed reluctor ring (tone wheel) and a sensor (which can be passive or active). The tone wheel is typically made of steel and maybe an open-air design, or sealed (as in the case of unitized bearing assemblies). The number of teeth is chosen as a trade-off between low-speed sensing/accuracy and high-speed sensing/cost. Greater numbers of teeth will require more machining operations and (in the case of passive sensors) produce a higher frequency output signal which may not be as easily interpreted at the receiving end, but give a better resolution and higher signal update rate. In more advanced systems, the teeth can be asymmetrically shaped to allow the sensor to distinguish between forward and reverse rotation of the wheel.

Accelerator Pedal Sensor

This sensor comprises a stator (which includes an excitation coil, receiver coils, and an electronic evaluation unit) and a rotor (formed of one or more closed conductive loops with a certain geometry). The application of alternating voltage to the transmission coil produces a magnetic field which induces voltages in the receiver coils. A current is also induced in the rotor conductive loops which, in turn, influences the magnetic field of the receiver coils. Voltage amplitudes are produced depending on the position of the rotor relative to the receiver coils in the stator. These are processed in an electronic evaluation unit and then transmitted to the control unit in the form of direct-current voltage. This evaluates the signal and forwards on the relevant pulse, e.g. to the throttle valve actuator. The characteristics of the voltage signal depend on how the accelerator pedal has been pressed.

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