Principle analysis of various types of flowmeters
(1) Principles of mechanics: Instruments belonging to such principles have differential pressure and rotor type using Bernoulli's theorem; impulse type and movable tube type using momentum theorem; direct mass type using Newton's second law; The target type of the momentum principle; the turbine type using the angular momentum theorem; the vortex type using the principle of fluid oscillation, the vortex type; the pitot tube type using the total static pressure difference; the volumetric type, the enthalpy, the trough type, and the like.
(2) Electrical principle: The instruments used for such principles are electromagnetic, differential capacitive, inductive, strain resistant, etc.
(3) Acoustic principle: Ultrasonic type, acoustic type (shock wave type), etc. are used for flow measurement using the acoustic principle.
(4) Thermal principle: The heat, direct thermal, indirect calorimetry, etc., which measure the flow using the thermal principle.
(5) Optical principle: laser type, photoelectric type, etc. are instruments belonging to such principles.
(6) Originally based on physical principles: nuclear magnetic resonance, nuclear radiation, etc. are instruments of this type.
(7) Other principles: Marking principle (trace principle, NMR principle), related principles, etc.
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.
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.