In order to make the electromagnetic flowmeter work stably and reliably, the following aspects should be noted when selecting the installation location:
1. Try to avoid ferromagnetic objects and equipment with strong electromagnetic fields (large motors, large transformers, etc.) to prevent the magnetic field from affecting the working magnetic field and flow signal of the sensor.
2. It should be installed in a dry and ventilated place to avoid sun and rain. The ambient temperature should be -20~+60°C, and the relative humidity is less than 85%.
3. There should be plenty of space around the flowmeter for easy installation and maintenance.
The measurement principle of the electromagnetic flowmeter does not depend on the characteristics of the flow. If there is a certain turbulence and vortex in the pipeline, it will be generated in the non-measurement zone (such as elbow, tangential current limit or half-opening shut-off valve upstream). Nothing.
If steady-state eddy currents in the measurement zone affect the stability of the measurement and the accuracy of the measurement, then some measures should be taken to stabilize the flow rate distribution:
a.increase the length of the straight pipe before and after; b. use a flow stabilizer; c. reduce the cross section of the measuring point.
Vortex flowmeter analysis and solution
6. The connection problem between the secondary instrument and the subsequent instrument. Due to the problem of the subsequent instrument or the maintenance of the subsequent instrument, the mA output circuit of the secondary instrument is interrupted. For this type of secondary instrument, this part is mainly related to the problem 2. Especially for the subsequent recorders, in the case that the recorder cannot be repaired for a long time, it is necessary to pay attention to shorting the output of the secondary meter.
7. The circuit always has no indication due to the failure of the secondary instrument flat-axle cable. Due to long-term operation, coupled with the influence of dust, the flat-axle cable is faulty, and the problem can be solved by cleaning or replacing the flat-axis cable.
8. For the problem 7, the main problem is that the secondary instrument shows that the fixing screw of the meter head is loose, causing the head to sink, the pointer and the case friction are large, the movement is not working, and the problem is solved by adjusting the meter head and re-fixing.
9. Use environmental issues. In particular, the sensor part installed in the well is affected by the humidity of the environment, which causes the circuit board to be damp. This part is mainly related to questions 2 and 2. Through the corresponding technical improvement measures, the sensor part with large humidity is re-separated from the probe part and the conversion part, and the separate type sensor is used. Therefore, the working environment is good, and the instrument has been running well.
10. Due to the poor adjustment of the site, or due to the actual situation after the adjustment. Due to the on-site vibration and noise balance adjustment and sensitivity adjustment is not good. Or because of the re-allocation of the situation after a period of operation after the adjustment, causing the indication problem, this part of the reason is mainly related to questions 4 and 5. Use an oscilloscope, plus the combined process operation, and re-adjust.
Some experiences on using ultrasonic flowmeter
1. The flowmeter has two modes, diagonal and reflective. When the reflection mode is not detected, it can be measured in diagonal mode, so that we have been using the reflection mode.
2. The flowmeter requires a relatively high pipe, and the insulation layer must be scraped off, otherwise it cannot be measured. When we measured the air conditioning water system, we cut the insulation layer with a knife to prevent the sensor. After the measurement, the cut insulation layer was glued. The surface of the pipe should be as bright as possible. If it is too rough, it must be sanded.
3. It is difficult to measure when the fluid in the pipeline is not full, so the measuring position should be as straight as possible, away from elbows, valves and other places.
4. The authenticity of the flowmeter reading depends on the signal strength. When the signal is too low, the result is basically unreliable, generally more than 60% or even more.
5. Since the readings may vary greatly, the approach we take is to have the flowmeter read continuously, such as continuously recording one minute of reading and then taking the average.
6. Measuring hot water lines is more difficult than cold water lines. Because the wall temperature of the hot water pipe is high, the coupling agent is easily formed at a high temperature. In addition to the product's own coupling agent, we have tried toothpaste.
The summary of ultrasonic flowmeter measurement accuracy and accuracy needs to be improved.