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.
Daily maintenance (2)
Converter check
If it is determined that the converter is faulty, if there is no problem in checking the external cause, please contact the manufacturer of the electromagnetic flowmeter. The manufacturer will generally solve the problem by replacing the circuit board.
Electrode maintenance
1. Before using the electromagnetic flowmeter, first calibrate the electromagnetic flowmeter with a standard pH solution. Before the calibration, before operation, you must pay attention to clean the electrode of the electromagnetic flowmeter with distilled water, and then clean the electrode again with the test liquid.
2. If you do not use the electromagnetic flowmeter, when you want to remove the electrode of the electromagnetic flowmeter, you should be careful not to let the electrode of the electrode collide with the hard object, otherwise the damage will affect the use of the electrode.
3. After using the electromagnetic flowmeter, you should put the electrode of the electromagnetic flowmeter on the sleeve, and put less saturated solution inside, just make sure that the bulb of the electrode is wet, but remember not to put it in distilled water. soak.
4. It is usually necessary to keep the electrode clean and do not let the output on both sides of it appear a short circuit. Otherwise, the measurement will be inaccurate and affect the use of the electromagnetic flowmeter.
In fact, there are still many ways to maintain the electrodes of the electromagnetic flowmeter. Everyone should pay more attention to the use process. Do not use the small negligence of the electromagnetic flowmeter in the future.
Ultrasonic flowmeter measurement principle
When the ultrasonic beam propagates in the liquid, the flow of the liquid will cause a small change in the propagation time, and the change in the propagation time is proportional to the flow velocity of the liquid, and its relationship conforms to the following expression.
among them
θ is the angle between the sound beam and the direction of flow of the liquid
M is the number of linear travels of the sound beam in the liquid
D is the inner diameter of the pipe
Tup is the propagation time of the sound beam in the positive direction
Tdown is the propagation time of the sound beam in the reverse direction
ΔT=Tup –Tdown
Let the speed of sound in the stationary fluid be c, the velocity of the fluid flow be u, and the propagation distance be L. When the sound wave is in the same direction as the fluid flow direction (ie, the downstream direction), the propagation velocity is c+u; otherwise, the propagation velocity is cu. Two sets of ultrasonic generators and receivers (T1, R1) and (T2, R2) are placed at two places separated by L. When T1 is in the forward direction and T2 transmits ultrasonic waves in the reverse direction, the time required for the ultrasonic waves to reach the receivers R1 and R2 respectively is t1 and t2, then
T1=L/(c+u); t2=L/(c-u)
Since the flow velocity of the fluid in the industrial pipeline is much smaller than the sound velocity, that is, c>>u, the time difference between the two is ▽t=t2-t1=2Lu/cc. Thus, the propagation velocity of the acoustic wave in the fluid is known. When it is known, the flow rate u can be obtained by measuring the time difference ▽t, and the flow rate Q can be obtained. The method of measuring the flow using this principle is called the time difference method. In addition, a phase difference method, a frequency difference method, or the like can be used.