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Vehicle Multi-Voltage Monitor

Want to monitor the battery voltage, the airflow meter signal or the oxygen sensor signal in your car? Here's the answer

By John Clarke

There are many voltages within a vehicle that can be monitored simply by attaching a meter to the source of the signal (or voltage) to be measured. This can give the driver information about the operation of various sensors and voltages within the engine bay.

When monitoring these voltages, it is not usually necessary to obtain a precise value of the voltage but the general trend of the voltage is sufficient.

Our Voltage Monitor provides for monitoring some of the most common voltages within a car. A 10-step bargraph lights LEDs in response to the measured voltage.

Click for larger image
Significantly larger than life size, this view of the SILICON CHIP Vehicle Voltage Monitor gives you a very good idea of how and where things go!

With low voltages applied to the Voltage Monitor, the low LEDs light and for high voltages, the upper LEDs light. Voltages in between are shown by the middle LEDs.

Some sensor voltages will alter simply due to the loading of a meter. Therefore, these require a meter that does not present any appreciable load on the sensor.

For example, the oxygen sensor that is used to monitor the correct burning of the fuel, typically has a voltage output between 0 and 1V, with the mid-way voltages indicating that the fuel is burnt correctly. A low voltage (near to 0V) indicates that the air-fuel mixture is too lean and a high value (approaching 1V) indicates a too-rich mixture. The voltage from these sensors also changes at a rapid rate as the engine management system continually monitors and changes the air-fuel mixture to ensure it is running at the correct (stoichiometric) mixture.

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