This sensor is particularly suitable for use in small spaces, such as the petrol tank of a motorbike. It has the advantage of not having any moving parts, unlike a conventional sensor with a float and float arm that make it difficult to fit in a tank. The sensor circuit is made from standard, inexpensive components and can be put together for little money. Petrol/Diesel Level Sensor Circuit Diagram : The operating principle is based on measuring the forward volt-ages of two identical diodes (check this first by measuring them). The forward voltage of a diode decreases with increasing junction temperature. lf a resistor is placed close to one of the two diodes, it will be heated slightly if it extends above the surface of the petrol. For best results,the other diode (used for reference) should be located at the same level. lf the diodes are covered by the petrol in the tank, the heating resistor will not have any effect because it will be cooled by the petrol. An opamp comp...