Accuracy class and function According to the measurement requirements and the use occasions, the instrument accuracy level is selected to achieve economical efficiency. For example, in the case of trade settlement, product handover and energy measurement, the accuracy level should be higher, such as 1.0, 0.5, or higher; for process control, select different accuracy levels according to control requirements; It is to detect the process flow, no need to do precise control and measurement, you can choose a lower accuracy level, such as 1.5, 2.5, or even 4.0, then you can use a low-cost plug-in electromagnetic flowmeter.
Measuring medium flow rate, meter range and diameter When measuring general medium, the full flow of electromagnetic flowmeter can be selected within the range of 0.5-12m/s of measuring medium flow, and the range is wider. The meter specification (caliber) is not necessarily the same as the process pipeline. It should be determined whether the measured flow range is within the flow rate range. That is, when the pipeline flow rate is too low to meet the flow meter requirements or the measurement accuracy cannot be guaranteed at this flow rate, It is necessary to reduce the gauge diameter, thereby increasing the flow rate inside the tube and obtaining satisfactory measurement results.
Try to avoid ferromagnetic objects and equipment with strong electromagnetic fields to prevent the magnetic field from affecting the working magnetic field and flow signal of the sensor.
Should be installed in the dry and ventilated place, to avoid sun and rain, the ambient temperature should be -20 ~ +60 ° C, relative humidity is less than 85%.
There should be ample space around the flowmeter for easy testing and maintenance.
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.
Turbine Flowmeter Product Introduction
A flow meter that uses a turbine for measurement. It first converts the flow rate to the speed of the turbine and then converts the speed into an electrical signal proportional to the flow. This flow meter is used to detect instantaneous flow and total integrated flow, and its output signal is frequency, which is easy to digitize. In the figure, the induction coil and the permanent magnet are fixed together on the casing. When the ferromagnetic turbine blade passes the magnet, the magnetic resistance of the magnetic circuit changes to generate an induced signal. The signal is amplified and shaped by an amplifier and sent to a counter or frequency meter to display the total integrated flow. At the same time, the pulse frequency is frequency-voltage converted to indicate the instantaneous flow rate. The speed of the impeller is proportional to the flow rate, and the number of revolutions of the impeller is proportional to the total amount flowing. The output of the turbine flow meter is a frequency modulated signal that not only improves the immunity of the detection circuit, but also simplifies the flow detection system. It has a turndown ratio of 10:1 and an accuracy of ±0.2%. Turbine flowmeters with small inertia and small size have a time constant of 0.01 seconds.
Turbine flowmeter is the main type of velocity flowmeter. When the fluid to be measured flows through the turbine flowmeter sensor, under the action of the fluid, the impeller is forced to rotate, and its rotational speed is proportional to the average flow velocity of the pipeline. At the same time, the blade periodicity The magnetic flux generated by the electromagnet is cut and the magnetic flux of the coil is changed. According to the principle of electromagnetic induction, a pulsating potential signal, that is, an electric pulse signal, is generated in the coil, and the frequency of the electric pulsation signal is proportional to the flow rate of the fluid to be measured.