1. The thermal anemometer is a meter used to measure the airflow speed. It is widely used because of its high measurement accuracy, ease of use, wide measuring range and high sensitivity. The thermal anemometer uses the calorimetric principle to measure the wind speed, and is mainly composed of a wind speed probe and a measuring indicating instrument. As the structure has a hot ball type and a hot line type, the display form has various types such as pointer type and digital type, but there are only two types according to the working principle, that is, constant current type and constant temperature type. The constant current type is a constant current for the wind speed sensitive component. After heating to a certain temperature, the degree of cooling with the change of the air flow is a function of the wind speed. The constant te
mperature type is adjustable for the current of the wind speed sensitive component. The operating temperature of the wind sp
eed sensitive component in different thermal equilibrium states is basically inconvenient at different wind speeds, that is, the resistance value is substantially constant, and the power consumed by the sensitive component is a function of the wind speed.
2. Working principle of constant current anemometer: The wind speed probe is a sensitive component. When a constant current passes through its heating coil, the temperature inside the sensitive component rises and reaches a certain value in the still air. At this time, the thermocouple of the measuring component therein generates a corresponding thermoelectric potential, and is transmitted to the measurement indicating system, and the thermoelectric potential and the reference back electromotive force generated in the circuit cancel each other out, so that the output signal is zero, and the meter pointer can also refer to Zero or zero value. If the heat sensitive component at the end of the wind speed probe is exposed to the external air flow, due to the heat exchange, the thermocouple thermoelectric potential will be changed at this time, and compared with the reference back electromotive force, a weak difference signal is generated, which is measured by the measuring instrument. The system amplifies and pushes the meter pointer change to indicate the current wind speed or the current wind speed value through the display after being processed by the microcontroller.
3. The constant temperature anemometer uses a feedback circuit to keep the temperature and resistance of the wind speed sensitive component constant. When the wind speed changes, the temperature of the heat sensitive component changes, and the resistance also changes, causing the voltage across the heat sensitive component to change. At this time, the feedback circuit plays a role, causing the current flowing through the heat sensitive component to change accordingly, and the system Restore balance. The above process occurs instantaneously, so the increase in speed is like an increase in the output voltage of the bridge, and the decrease in speed is also equal to the decrease in the output voltage of the bridge.
4. Three cups of eddy current sensor: The rotating shaft of the wind cup is a metal toothed turntable, and the induction head is composed of a
coil. The coil is connected to a high-frequency alternating current, and an alternating magnetic flux is generated around the coil. The metal tooth forms a closed circuit, and the metal tooth generates an eddy current. The metal tooth generates an alternating magnetic flux in addition to the heat dissipation, resulting in an alternating magnetic flux in the opposite direction. The inductance of the coil is reduced and a change in impedance is caused. When the rotating shaft rotates, a change of the magnetic flux of the coil is caused to output a continuous pulse signal, and the pulse signal is counted to calculate the rotational speed of the rotating shaft.
5. Three cups of optocoupler sensor type sensor
, when the wind cup rotates, the multi-tooth turntable is rotated by the main shaft, so that the lower photo transistor receives the light irradiated by the upper LED, and is turned on or off, forming a speed with the cup. The proportional frequency signal is counted by the counter and converted to the actual wind speed value.
Wind Sensor 