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speedometer won't go back to zero
The reasons why the automobile tachometer did not return to zero are as follows:
1.The speedometer in the total distance of the vehicle instrument failed, resulting in the tachometer pointer not rotating;
2.The mileage sensor of the vehicle has a fault. Check whether the flexible shaft connection is disconnected to see whether the mileage is beginning to increase. If the tachometer just doesn't work, you have to replace it with a new one;
3. There are foreign matters in the instrument that are stuck and cannot be moved. Open the instrument and remove the foreign matters inside. The tachometer is usually set in the instrument panel and placed symmetrically with the speedometer. The tachometer works according to the magnetic principle. It receives the pulse signal generated when the primary current in the ignition coil is interrupted and converts this signal into a displayable speed value. The faster the engine rotates, the more pulses generated by the ignition coil, and the larger the speed value displayed on the meter.
How to do:
If it doesn't return to zero after the ignition is off, it's an instrument problem. It's good to change the dial. However, if it doesn't return to zero when the car is on board, it's normal:
1. Tachometer is an instrument that can measure and display the speed of rotation. The measured objects can be shafts, discs, even motors or other machines;
2. Rotational speed is the physical quantity of the ratio of the number of revolutions of a rotating body to time. In engineering, it is usually expressed as rotational speed = number of revolutions \ / time, which is an important parameter to describe the rotational motion of an object;
3. Electricians often need to measure the speed of motors and their driving equipment, using portable tachometers;
4. Tachometer is an instrument used to measure motor speed and linear speed. There are many kinds of tachometers, including mechanical centrifugal tachometers and digital electronic tachometers.Cars are generally electronic tachometers, including pointer type and LCD digital display type. There is a digital integrated circuit in the meter, which drives the pointer to move or digital display after calculating the voltage pulse transmitted from the ignition coil. In addition, there is another tachometer that takes out the pulse signal from the generator and sends it to the tachometer circuit to explain and display the speed value. However, due to the influence of factors such as generator belt slipping, the value is not accurate.
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