is currently used in industrial production is quite common, especially in the areas involved in flow measurement is more common, and even many large diameter water company is in the use of electromagnetic flowmeter for measuring the water, this article is for the measurement of air conditioning chilled water case analysis, specific as follows: a airport hotels get chilled water for air conditioning energy center from the airport.
In winter season frozen water outage, in and out of the hotel's road mark valve closed cooling water pipe, electromagnetic flowmeter is refers to the full value.
Stop cooling, but still full of water in the chilled water pipe in the cooling system, energy company general with cold water as refrigerant provided to the user.
The refrigerant in addition to fresh water, salt water, sometimes also USES a mixture of water and alcohol and ethylene glycol, etc. , to meet the needs of different temperature levels.
In aim to air conditioning and cooling systems, usually use fresh water, often take 5 - water supply temperature
These freshwater after dosing process, to prevent the water of oxygen corrosion on pipe wall.
During the winter season, though has stopped cooling, in-line water stop cycle, but still let fresh water pipeline, prevent the air into pipeline, pipe inner surface rust.
Electromagnetic flowmeter for atc's ability to adapt now the scene using electromagnetic flowmeter, the vast majority of atc adaptability are poor, which do not allow the measuring tube hollow tubes, because once the measuring tube hollow tubes, electrode exposed to air, will be induced by the signal source resistance particularly big interference excitation coil, lead to flow up to full value.
In this case, electromagnetic flowmeter refers to the full should also be caused by measuring tube hollow tubes.
Why atc air conditioning chilled water system should be filled with water at ordinary times, but because of the hotel equipment maintenance, the water emptying, finished repair and forget to open the valve into the water, resulting in atc.
Atc detection and atc zero electromagnetic flowmeter is specially designed for measuring the volume flow of conducting liquid.
Measuring principle is based on Faraday's law of electromagnetic induction.
According to the law of the conductive fluid through magnetic field for cutting lines, produced in the perpendicular to the direction of the magnetic field and the velocity of induction electromotive force, the electromotive force by 4.
Type 4 in 14 day.
The principle is shown in figure 4.
For years people are looking for atc testing and atc method of zero.
32 is a domestic company has been successfully using the method of this method is based on the electrical conductivity measurement.
In figure 4.
32, the resistance between the two electrodes are available (
Said: type: Re—
Resistance between electrodes;
Electrode factor (
The sounding pipe diameter) and size of the electrode
From the type,
: the type of symbol meaning and type (
For tap water, acid and alkali solution, Re full tubes is about 1 o & Omega;
- - - - - -
And atc, the liquid level is lower than electrode, on the principle of Re for infinity.
Due to the tube wall between two electrodes could damp, Re actually only limited value, but is much bigger than normal operation when the resistance value.
Generally determine whether Re values in normal operation of the air resistance value of 3 times.
Instrument once ruled catheter for atc, instrument of the single chip microcomputer is two steps, first is to make the output is zero, the second is a atc alarm signals, thus eliminating atc error measurement or error control.
Atc refers to the full and security atc refers to full one major drawback is the electromagnetic flowmeter, easy to give a person with illusion.
Especially in flow meter
output signal is used to automatically adjust when the illusion is easy to make the regulator ran to the limit position, so we should pay attention to safety.
The full package testing electromagnetic flowmeter is one of the speed meter.
It gives the signal through the measuring tube is actually mean velocity of liquid, liquid in the measuring tube is full of cases, the type,
Founded: type, qv—
Sounding pipe flow area;
The average flow velocity.
But if there is not the full package, as part of the catheter cross-sectional area occupied by A gas, so that actual circulation sectional area is smaller than A liquid, and lead to traffic after the value is on the high side.
Lots of electromagnetic flowmeter is applied in water supply and water supply and drainage, water flow in a horizontal pipe, often because of temperature change and product gas, and gathered at the top of the horizontal line.
If has had its own gas, electromagnetic flowmeter measurement tube at the top of the instrument of high precision characteristics will sell at a discount greatly, so the full package testing has long ago as the researcher's subject.
The full package testing is based on the conductivity detection method.
In figure 4.
33 in the electromagnetic flow sensor, added a (
Or a pair)
The full package testing electrode.
When intraductal liquid filled tube, the top electrode and the resistance value between the other electrode is;
When the presence of a full package, between the top electrode and the conductive liquid gas cut off, so the electrode resistance increases significantly, thus make the full package judgment.
Electromagnetic flowmeter in the full package, processing method is usually at the top of the flow measurement pipe upstream pipe set exhaust valve.
Instrument science and technology in this paper by embellish release, if you encounter any problems in the process of using the instrument, can call our domestic sales service hotline: 0517 -
86917118, we have * * personnel unriddling for you)
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