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Trouble phenomenon and treatment of electromagnetic flowmeter converter
Trouble phenomenon and treatment of electromagnetic flowmeter converter
Data: 2020-08-21 08:27

Trouble phenomenon and treatment of electromagnetic flowmeter converter

1 No display on the meter

1.1 Black screen (the meter does not work, it is the same whether it is powered on or not)

 Check whether the power is on

 Check whether the fuse is in good condition

 Check whether the power supply voltage meets the requirements (24V converter may be the power supply is reversed)

 Use a multimeter to measure whether the converter has a current output. If there is an output, it means that the meter is working normally. It may be that the LCD is in poor contact or broken. You can replace the LCD to eliminate it.

 If the above items are normal, the converter is broken and should be returned to the factory for repair.

2 2.1 White screen or black screen (with backlight without display)

 Adjust the contrast in the measurement state

 Use a multimeter to measure whether there is current output

 If there is output, you can replace a liquid crystal of the same model under conditions or check whether the contact between the LCD and the motherboard plug-in is reliable, press the contact.

 If the causes of the above faults are eliminated, return to the factory for repair.

- 1 -2 The fuse bursts after powering up and cannot be powered on

 First determine whether the converter has been struck by lightning. If it has been struck by lightning, return to the factory for repair

 Check the appearance of the fuse, if the fuse is seriously damaged, return to the factory for repair

 If the first two can be eliminated, check whether the on-site power supply meets the requirements and whether the power supply voltage matches the voltage of the converter

 If it is not caused by overvoltage, you can replace the fuse that matches the converter voltage (for 220V, replace the 2A fuse, and for 24V, replace the 4A fuse), and power on again. If this phenomenon still occurs, you must return to the factory for repair .

3 Excitation alarm

 If this kind of failure occurs during the initial installation and commissioning of the instrument, check whether the excitation coil resistance of the sensor is in phase with the excitation current of the converter.

match

 If it matches, check the excitation wiring for open circuit or poor contact

 If all the above are normal, return to the factory for repair.

4 Air traffic alarm

 Check whether the on-site air pipe valve is tightly closed

 Check whether the pipeline is empty

 Check whether the ATC alarm setting is turned on

 Determine whether the threshold setting is appropriate

 If the on-site pipeline is empty, but the converter has a flow display. In this case, first reduce the threshold value (less than the current value) until the flow is completely cut off, and then add the normal flow to observe whether it affects the actual measurement. If there is an impact, increase the threshold appropriately. In short, the principle of the threshold setting is that it neither affects the actual measured value, but also cuts the flow to zero.

5 The measured flow is not accurate

 Check whether the signal line connection is normal

 Whether the fluid is full of the measuring tube

 Check whether the set parameters match the label. In addition, you should understand on what basis users judge the inaccuracy of traffic.

 When the difference between the actual measured value and the user's ideal value is not too much, it is recommended that the user modify the sensor calibration coefficient (the sensor coefficient is proportional to the flow rate).

 If the flow rate is still inaccurate, return to the factory for repair.

6 Screen flicker

 Check whether the power supply voltage meets the requirements

 If it is a 24 volt power supply converter, sometimes the 220 volt power supply is incorrectly connected, and the screen flicker may occur when the power is turned on again.

 The power of 24 volt power supply in some sites is not enough, which can also cause screen flicker on the converter with 24 volt power supply.

 Whether the contact between the LCD and the motherboard plug-in is reliable, the LCD plug can be re-plugged

 Check whether the ground wire is connected to the correct position. If the ground wire is connected to the excitation EX+, there will be screen flickering.

 If all of the above may be excluded, return to the factory for repair

7 Unsteady flow

 If the user has conditions, it is recommended to use a signal source for calibration. If the flow rate is normal, check whether the site environment has any influence on the converter, such as external electromagnetic interference.

 Demonstrate whether the verification medium is the factor causing the flow instability.

 Check whether there is vibration in the pipeline, which causes unstable flow

 If all of the above may be ruled out, return to the factory for repair.

8 No current output

 Determine whether the flow rate display of the converter is normal. If it is normal, check whether the parameter settings are changed. The current output status is set, and the current output type of the converter is determined

 Test directly with a multimeter, and remove the external equipment first

 If it is a 411 type converter, under the normal conditions above, you can check whether the motherboard cable is plugged in. (This processing method is limited to our company's dealers)

 If all the above are excluded, the converter is broken and should be returned to the factory for repair.

9 No frequency (pulse) output

 Determine whether the flow rate display of the converter is normal

 Use a frequency counter (oscilloscope) to test directly, and remove the external equipment first

 Determine the pulse output mode selection frequency (pulse) of the converter

 Note: If it is a square 211 converter, the DIP switch 1 should be set to ON, at this time it is frequency output.

10 Parameter disorder

 Record the original data, reset the converter parameters, and then input the data-5-6-and observe the operation for a period of time. If this phenomenon occurs repeatedly, return to the factory for repair.

11 Leakage

 Check whether the converter shell is installed with a ground wire and the ground is intact.

 Check whether the power cord touches the shell.

12 Sometimes there is no pulse and frequency when connected with PLC

The converter is connected to the PLC in pulse output mode, sometimes there is no pulse. There are two meters on site, one is normal and the other is sometimes absent. The pulse output of PLC is normal without connecting. Later, it was found that the connection was not a shielded wire, but a normal wire. It was suspected that there was interference between the wires, and the pulse output of two temporary wires was normal.

13 Phenomenon: The flow value displayed by the PLC system is the actual

the fixed electromagnetic flowmeter shows 50% of the value, and the PLC system responds to the instantaneous flow by receiving the 4-20 mA of the electromagnetic flowmeter.

Troubleshooting:

1,

Disconnect the current output terminal of the flowmeter from the PLC and the inverter, and measure the output current of the electromagnetic flowmeter to match the actual flow displayed on the meter;

2,

Connect the 4~20mA output to the PLC (disconnect the inverter), and the flow displayed on the head of Table 7 matches the flow displayed by the PLC;

3,

Then turn on the inverter, the PLC display flow rate is 50% of the electromagnetic meter head display flow rate. The reason is obtained after measurement: the PLC receives the 1~5V signal, and the 4~20 mA signal is converted into the 1~5V signal through the 250 ohm resistor connected in parallel at the input terminal, and the measurement shows that the input terminals of the PLC and the inverter are respectively combined If a 250 ohm resistor is connected at the same time, it is equivalent to 500 ohms connected to 4-20 mA, and the 4-20 mA is converted to 0.5-2.5V signal and provided to the PLC for display.

Correct: Electromagnetic output 4~20 mA---﹥PLC (and 250 ohms) receiving (1~5V)---﹥Flow rate display is consistent;

Error: Electromagnetic output 4~20 mA---﹥PLC (and 250 ohms)/Inverter (and 250 ohms) = (and 500 ohms) PLC receiving (0.5~2.5V)

Therefore: PLC display flow value is half of the actual flow value.

Solution: Remove the 250 ohm resistor connected in parallel to the inverter to ensure that the flow rate display is normal and consistent at the same time. 14. Once the integrated converter and the sensor are connected tightly, the screen will be black.

 Check whether the thread is broken.

 Check if the LCD cable is crushed by the LCD frame and short-circuited with the bracket.

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