Sewage flow sensor with pipe buried in the ground apply, sensors are IP68 protection structure, converter installed in instrument box or indoor, both through the cable connection, due to ground subsidence, mountainous environment humid site conditions change, such as sensors and switches is not completely ready cable moistureproof joint (waterproof), and other processing. At the joint in a moist environment, such as instrument, in cable trench, well, moisture intrusion cable joint, have the cause of the following may:

(1) excitation coil to ground insulation, small measurement result;

(2) excitation loop cable joint contact resistance, make converter excitation circuit is in the constant current work area, excitation current, the same small measurement result, if the contact resistance is not stable, the measured value fluctuate.

(3) line to ground insulation drops, causes the signal attenuation, final measurement results is small;

(4) signal excitation lines of insulation performance, makes the measurement result is greater than the normal data, such as the interference is not stable, the hot water flow sensor instrument and the influence of uncertainty, and volatility;

(5) the signal cable joint contact resistance, the measured value smaller, if the contact resistance is not stable, the measured values cannot be stable, and easy to introduce interference;

Anomalies due to occur in the above signal circuit, has the certain difficulty, only field, after rule out other circulating water flow sensor fault, you should check whether there is cable problem, field instrument maintenance personnel as long as the field excitation loop resistance measurements and data provided by the manufacturer, the test grounding resistance, step by step to determine the problem, then take measures, or replace the whole cable, or stay cable joint dry, etc.

Sewage flow sensor inside the rotor is more than a year, basically not failure, but a year later, will often appear abnormal work, specific performance for measuring value becomes large or small, or keep fluctuations, and through on-site inspection, has ruled out pipe discontent, medium the possibility of the phenomenon such as gas, found the problem may be related to cable fault likely also.