According to the conductivity of sewage

it is simple and practical to use electrodes to measure sewage level.Because the conductivity of sewage varies with composition and temperature

it is not suitable to measure conductance to obtain sewage level by electrodes.To solve this problem

a new technique is presented to measure liquid level by four electrodes.The theoretical analysis and experiment results indicate that the liquid conductivity has no influence on the measurement of liquid level by four electrodes.The new technique is suitable for the level measurement of sewage which changes in temperature and composition.