System express diagnostics of quality fuels and lubricants

Abstract

Humidity of fuels and lubricants is one of the determining indicators of their quality. The presence of moisture in the material affects their physicochemical and electrical properties. Water is characterized by high dielectric constant and the ability to easily interact with other substances.

The development of a humidity control system for fuels and lubricants during the operation of the machine is an integral part of the information-measuring and control systems of modern mobile equipment, and in particular special purpose vehicles.

Capacitive humidity sensors are distributed structures and in measuring systems the measurement parameters are both capacitance and resistance and inductance. To implement a capacitive meter with a linear graded characteristic, it is taken into account that the measuring medium is with large variable active losses, which are oils and fuels of internal combustion engines. To compensate for the active losses, a circuit with a separate measurement of the reactive component of the impedance of the dielectric primary transducer based on the modulation of the parameters of the measuring resonant contour is used. The parameters of such a circuit are chosen so that when the modulation capacitor is disconnected, the full conductivity of the circuit had an inductive nature.

The quality of the transformation of the measuring circuit of the sensor is adopted by the differential sensitivity, which characterizes the ratio of the relative increments of the output (full conductivity) and input (reactive conductivity) parameters.

An automatic single-frequency meter with a capacitive sensor made in the form of electrodes scattered field electrodes covered with an insulation layer has been developed, in which the method of modulation of the parameters of the measuring resonant circuit is used. To verify the theoretical studies, a complete factorial experiment was performed at three levels with two factors - the humidity of the test medium and the frequency of the supply voltage of the measuring contour.

The efficiency of the measuring circuit of the capacitive transducer is maintained in the entire range of measurements, if the quality factor of the capacitive measuring transducer in the material is greater than one.