How to judge the quality of electromagnetic flowmeter

Using the visualization method and the instrument method, use GS8 to check whether the resistance coil of the sensor, the insulation resistance between the signal lines, the grounding resistance and other items meet the pre-compliance standard, and whether the electromagnetic flowmeter converter meets the accuracy requirements regardless of zero point and output current. The specific detection method is:

1. Measure the resistance value of the excitation coil to determine whether there is an inter-turn short circuit in the excitation coil (resistance between line numbers "7" and "8"), and the resistance value should be between 30 ohms and 170 ohms. If the resistance is the same as the factory record, the coil is considered good, and the magnetic field strength of the electromagnetic flowmeter sensor is not evaluated indirectly.

2. Close the valve on the pipeline, when the electromagnetic flowmeter is full of liquid and the liquid does not flow, check the zero point of the whole machine. Make appropriate adjustments as needed.

3. Check the insulation resistance of each core wire of the signal line and the excitation line, and check whether the shielding layer is intact.

4. Use the GS8 calibrator to test the output current of the converter. When given zero flow, the output current should be: 4.00 mA; when given 100% flow, the output current should be: 20.00 mA. The error of the output current value should be better than 1.5%.

5. Measure the insulation resistance of the excitation coil to the ground (measurement numbers "1" and "7" or "8") to determine whether the sensor is wet, and the resistance value should be greater than 20 megohms.

6. Measure the contact resistance between the electrode and the liquid (measure the numbers "1" and "2" and "1" and "3"), and indirectly evaluate the general condition of the electrode and the surface of the lining layer. Whether the deposited layer is conductive or insulating if the electrode surface and backing layer are attached to the deposited layer. The resistance between them should be between 1 kohm and 1 megohm, and the resistance values of wire numbers "1" and "2" and "1" and "3" should be approximately symmetrical.

7. Test the excitation current value (between converter terminals "7" and "8"), the positive and negative excitation currents should be within the specified range, about 137 (5%) mA.