Application failure of metal tube flowmeter of electronic measuring instrument

1. Pointer jitter:

1. Slight pointer jitter: generally caused by medium fluctuations. It can be overcome by increasing damping.

2. Moderate pointer jitter: generally caused by the flow state of the medium. The gas is generally caused by unstable operating pressure of the medium. A stable voltage or steady flow device can be used to overcome or increase the gas damping of the float flowmeter.

3. Severe pointer jitter: Mainly due to medium pulsation, unstable air pressure, or pressure, temperature, and flow rate of the gas operation state given by the user, which does not match the actual state of the float flowmeter, a large difference causes the float flowmeter to overrange.

2. The main reason why the pointer stops at a certain position is that the float of the float flowmeter is stuck.

Generally, when the metal tube float flowmeter is used, the valve is opened too fast, so that the float quickly hits the stopper, causing the stopper to deform and block the float. But it cannot be ruled out that the float guide rod and the stop ring are not concentric, causing the float to be stuck.

During processing, the instrument can be disassembled, the deformed stopper can be removed and reshaped, and check whether it is concentric with the guide rod. If it is not concentric, it can be corrected, and then install the float, push the float by hand, and feel that the float is unobstructed up and down. But, in addition, when installing the float flowmeter, it must be installed vertically or horizontally, and it cannot be tilted, otherwise it will easily cause card meters and bring errors to the measurement.

3. Large measurement error

1. The installation does not meet the requirements. For the vertically installed metal tube float flowmeter, keep it vertical, and the inclination angle is not more than 20 degrees. For the horizontal installation float flowmeter, keep it horizontal, and the inclination angle is not more than 20 degrees. There must be no ferromagnetic objects in the 100mm space around the float flowmeter. The installation location should be far away from the valve reducing port, the pump outlet, the process pipe turning, etc. To maintain the requirements of 250mm straight pipe section before the first 5D.

2. A large change in the density of the liquid medium is also a cause of large errors. Before the meter is calibrated, the medium is converted according to the density given by the user, and converted into the flow rate of water in the calibration state for calibration. Therefore, if the medium density changes greatly, it will cause a large error in the measurement. The solution is to bring the changed medium density into the formula, convert it into an error correction factor, and then multiply the flow rate measured by the flow meter by the factor to convert it into a true flow rate.

3. Because the gas medium is greatly affected by temperature and pressure, it is recommended to use temperature and pressure compensation to obtain the true flow rate.

4. Due to multiple factors such as long-term use and pipeline vibration, the moving parts of the metal tube float flowmeter, such as sensing magnets, pointers, counterweights, rotating magnets, etc., are loose, causing large errors. Solution: It can be verified by pushing the pointer by hand first. First press the pointer to the RP position to see if the output is 4mA and the flow rate display is 0%, and then verify in turn according to the scale. If a discrepancy is found, the position of the parts can be adjusted. Generally, professionals are required to make adjustments, otherwise the position will be lost, and it needs to be returned to the manufacturer for correction.

4. No current output

1. First see if the wiring is correct.

2. Whether there is display on the LCD, if there is no output, it is mostly because the output tube is broken, and the circuit board needs to be replaced.

3. Lost calibration value. Due to the failure of E2PROM, the calibration data of the instrument will be lost, and there will be no output current, and the current will remain unchanged. Solution: The data recovery operation can be used. If it does not work, you can first set the data in the password 2000, and then set the data in the password 4011. The method is to manually calibrate the data from RP to 100% by pushing the pointer.

5. No on-site display

1. Check whether the wiring is correct.

2. Check whether the power supply is correct.

3. Re-install the LCD module and check for improper contact.

4. For the multi-wire power supply mode, check whether terminals 12 and 13 are connected to an ammeter or short-circuited.

6. On-site LCD always displays 0 or full scale

1. Check the range and zero parameters set in the 2000 password. ZERO is required to be less than the value of SPAN, and the two values ​​cannot be equal.

2. Check whether the sampling data is up, push the pointer with your hand to see the change of the sampling value. If there is no change, the circuit board sampling circuit is generally faulty and the circuit board needs to be replaced.

7. The alarm is incorrect

1. Check the deviation setting d value can not be too large.

2. In the FUN function, whether the logic function is correct. HA-A means positive logic of upper limit. LA-A means lower limit positive logic.

3. Check the set value of alarm value in SU.

4. If the LCD bar code indication is correct and the output has no action, you can check whether the external power supply and the negative pole of the external power supply are connected to the negative pole of the power supply of the instrument.

5. The circuit board is faulty, replace the circuit board.

8. Accumulated pulse output is incorrect

1. Check whether the alarm value of the channel selected for cumulative pulse output is set to zero.

2. The circuit board is faulty. Replace the circuit board.

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