Working principle of thermal bulb anemometer
The hot bulb anemometer consists of two parts: a hot bulb sensor and a measuring instrument. The head of the sensor has a tiny glass sphere with a nichrome wire coil that heats the glass and two thermocouples connected in series. The cold end of the thermocouple is connected to the phosphor bronze pillar and is directly exposed to the airflow. When a certain size of current passes through the special coil, the temperature of the glass bulb rises. The degree of increase is related to the speed of the airflow. The flow rate is small. The degree of increase is large, whereas the degree of increase is small. The magnitude of the rise is indicated on the ammeter by a thermocouple generating a potential. Therefore, after calibration, the meter reading can be used to indicate the speed of the airflow.
The thermal bulb anemometer is a portable and intelligent low wind speed measuring instrument, which is used in measuring pipeline environment and heating, air conditioning and refrigeration, environmental protection, energy saving monitoring, meteorology, agriculture, refrigeration, drying, labor hygiene investigation, clean workshop, chemical fiber textile , various wind speed experiments, etc. have a wide range of uses.
The wind speed test includes the test of the average wind speed and the test of the turbulence component (wind turbulence 1 ~ 150KHz, different from the fluctuation). There are thermal, ultrasonic, impeller, and Pitot tube methods for testing the average wind speed.
The measurement range of flow velocity from 0 to 100m/s can be divided into three sections: low velocity: 0 to 5m/s; medium velocity: 5 to 40m/s; high velocity: 40 to 100m/s. The thermal probe of the anemometer is used for the maximum measurement of 0 to 5m/s; the rotating wheel probe of the anemometer is ideal for measuring the flow velocity of 5 to 40m/s; and the pitot tube can get the best results in the high speed range . An additional criterion for the correct selection of an anemometer's velocity probe is temperature, usually the thermal sensor of an anemometer is used at a temperature of about +-7˚C. The rotor probe of the special anemometer can reach 35˚C. Pitot tubes are used above +35˚C.
The thermal bulb anemometer is an instrument capable of measuring low wind speed, and its measurement range is 0.05-10m/s. The hot bulb anemometer is composed of two parts: a hot bulb rod probe and a measuring instrument. The probe has a glass ball with a diameter of 0.6mm, and the ball is wound with a nickel-chromium coil for heating the glass ball and two thermocouples connected in series. The cold junction of the thermocouple is attached to a phosphor-bronze post exposed directly to the air flow. When a certain amount of current passes through the heating ring, the temperature of the glass bulb rises. The degree of increase is related to the wind speed, and the degree of increase is large when the wind speed is small; otherwise, the degree of increase is small. The magnitude of the rise is indicated on the meter by means of a thermocouple. According to the reading of the electric meter, check the calibration curve to find out the wind speed (m/s).
