Variable gap plate capacitive sensor is developed based on the principle of diesel dielectric constant measurement.According to the measurement requirements

peripherals auxiliary circuit of sensor is designed

the core control part is AT89C51 MCU

AD9852 is used as excitation signal source

to generate different frequency and amplitude of sinusoidal signal to be applied to the detection and reference sensors

through follow-up zoom

filtering and A/D conversion

the obtained signal is transformed into a non-dimensional data related to dielectric constant.With variable gap measurement of the degree of oxidation of diesel samples

repeatability and differences of sensors are investigated

and the best ideal distance 0.6mm is determined.