Signal of electromagnetic flowmeter. Generally, the electromagnetic flowmeter can operate normally for a long period of time under the premise of no maintenance after installation. It must be maintained and inspected in the future. Sometimes the small signal of the electromagnetic flowmeter may occur, so there is no need to be surprised. If you do the following procedures carefully, you can solve it.
1.The mechanism of small signal
Electromagnetic flowmeters are subject to deviations and are very susceptible to interference, such as "small signal" conditions, in the precise and precise measurement scene and production process. According to the principle of electromagnetic flowmeters, the interference problems of electromagnetic flowmeters are caused by various excitation methods.
The following difficulties exist in many processing plants at this stage:
(1) When the pump is started, the liquid cuts the magnetic induction line according to the flowmeter, which causes a flow signal. This liquid is finally used in the post-mortem phase. The flow measurement value is reasonable and a total should be carried out. There will still be a small amount of liquid flowing back in the road, and cutting the magnetic induction line in the opposite direction will also cause a small signal, but this liquid is not used by the specific manufacturing, and the steam flow meter will still transmit the signal to the PLC for sampling. Will lead to large deviations.
(2) Because there is external vibration or a large magnetic field interference, when there is no material mobility, external vibration and other signals are effective for the controller, and the "misflow" signal is introduced. When such signals are higher than the metering low limit of the dashboard, they are total.
(3) The surface of the electrode is adhered with a layer of insulation, subjected to external interference, or the mAh signal sent by the electrical level has a zero drift during the enlargement and conversion process, which causes the signal to shift from the standard value and cause deviation.
All of the above conditions belong to the small signal condition.
2, small signal solution
The small-signal problem caused by interference signals cannot be processed from the process technology, but only to find a processing method from the process control level. Can be handled according to two methods of hardware and mobile phone software.
The hardware configuration method can be composed of more power circuits and electronic switches. This type of method is suitable for filtering out interference signals, but it will increase the company's product cost. Because there are many flowmeters in a process section, relatively many units need to be replaced. This instrument.