How to choose anemometer to carry out air conditioning system inspection
Air conditioning system testing usually requires anemometers to measure the wind speed of the wind system. According to the principle, it can be divided into many types. The conventional ones include impeller type, cup type anemometer, and Pitot Tube.
In air conditioning system testing, because the impeller anemometer occupies a large area of the air duct, it affects the wind speed distribution indoors or in the duct, and has low sensitivity to low wind speeds, so it is basically unusable. Many people see the cheapness of the impeller and do not buy it. suitable. The impeller type can usually be used for outdoor testing. For example, the green building standards stipulate that the wind speed in the pedestrian area around the building is less than 5m/s, which does not affect the comfort of outdoor activities and building ventilation.
The Pitot Tube seems to be a method of measuring wind speed invented by a man named Pitot. The principle is to measure wind speed through dynamic pressure difference. The sensitivity of the Pitot Tube mainly depends on the sensitivity of the micro-pressure differential meter it uses. Considering that the pressure is below 1Pa The uncertainty of the difference is already very high (if you are interested, you can infer the wind speed corresponding to 1Pa, which may be 0.xm/s), so the accuracy of its measurement is also limited. Another problem is that the limitation is that the value obtained is the pressure difference, and the user also needs to convert the pressure difference.
If a digital micromanometer with an accuracy higher than 1 Pa is used, its price is tens of thousands, and the price is already close to that of a cup anemometer. If you use an alcohol-based inclined tube micromanometer, the price of a domestically produced instrument that can guarantee accuracy is around a few hundred yuan, but you must use absolute alcohol (about 95% purity). If you carry out the business of air conditioning system testing, you need to calibrate the inclined tube micro-pressure differential meter of alcohol. In fact, it is mainly to calibrate the specific gravity of alcohol. However, alcohol is easy to volatilize after long-term use within a calibration cycle (usually 1 year). After volatilization, configure Alcohol, the calibration results of the inclined tube micromanometer are difficult to guarantee. Because air-conditioning system testing requires on-site inspection, this inclined tube differential pressure gauge cannot be used on many means of transportation due to restrictions such as air traffic control.
In short, although the Pitot tube + inclined tube micro-pressure differential meter is a cheap configuration, its operation, use and calibration are very cumbersome to achieve ideal wind speed measurement accuracy. If you use a Pitot tube + digital micro-pressure differential meter, the price is almost the same as a cup-type anemometer. The advantage is that the high-precision micro-pressure differential meter used here can also measure micro-pressure differences and measure other physical quantities.
Therefore, the most commonly used anemometer for air conditioning system testing is the cup-type anemometer. Hot bulbs are not recommended here because the hot bulbs of many hot bulb anemometers are not strong enough. For example, TESTO has a disposable one with a retail price of less than 800 yuan. The anemometer (actually OEMed from a factory in Taiwan) has a narrow measurement range and the mechanical strength of the thermal bulb is very low. If the wind speed is slightly higher, it will be blown off and cannot be repaired. If you choose to use a ** anemometer, I will open another article to discuss it.
