When the flow meter is put into operation or it is found that the meter is not working properly after a period of normal operation, the external conditions of the flow meter should be checked first, such as whether the power supply is good, whether the pipeline is leaking or in a state of partial pipe, whether there are bubbles in the pipeline, whether the signal cable Damaged, whether the output signal of the converter (that is, the input circuit of the subsequent instrument) is open. Remember to dismantle and repair the flowmeter blindly.
Test equipment: a 500MΩ insulation resistance tester and a multimeter.
(1) When the pipeline is full of medium, use a multimeter to measure the resistance between terminals A, B and C. The resistance between A-C and B-C should be approximately equal. If the difference is more than 1 time, it may be that the electrode is leaking, the outer wall of the measuring tube or the condensation water in the junction box may be adsorbed.
(2) When the lining is dry, use a MΩ meter to measure the insulation resistance between A-C and B-C (should be greater than 200MΩ). Then use a multimeter to measure the resistance between terminals A and B and the two electrodes in the measuring tube (should be in a short-circuit connection state). If the insulation resistance is very small, it means the electrode is leaking, and the entire flowmeter should be returned to the factory for repair. If the insulation has dropped but there is still more than 50MΩ and the inspection result of step (1) is normal, it may be that the outer wall of the measuring tube is damp, and a hot air blower can be used to dry the inside of the housing.
(3) Use a multimeter to measure the resistance between X and Y. If it exceeds 200Ω, the excitation coil and its lead wire may be open or poorly connected. Remove the terminal board and check.
(4) Check the insulation resistance between X, Y and C. It should be above 200MΩ. If it drops, use hot air to dry the inside of the shell. In actual operation, the decrease of the insulation of the coil will cause the measurement error to increase and the output signal of the instrument is unstable.
(5) If it is determined that the sensor is faulty, please contact the manufacturer of the electromagnetic flowmeter. Generally, it cannot be solved on site and needs to be repaired by the manufacturer.
If it is determined that the converter is faulty, if there is no problem after checking the external cause, please contact the manufacturer of the electromagnetic flowmeter. The manufacturer will generally adopt the method of replacing the circuit board.