working principle:
A speed measuring instrument that converts a flow rate signal into an electrical signal that also measures fluid temperature or density. The principle is that a thin wire (called) electrically heated is placed in the airflow, and the amount of heat dissipation in the airflow is related to the flow rate, and the heat dissipation causes a temperature change to cause a resistance change, and the flow rate signal is converted into an electrical signal. It has two working modes: 1 constant current. The passing current remains unchanged. When the temperature changes, the resistance changes, so the voltage at both ends changes, thereby measuring the flow rate; 2 constant temperature type. The temperature remains the same, such as maintaining 150 ° C, the flow rate can be measured according to the current applied. The thermostatic type is more widely used than the constant current type.
The length is generally in the range of 0.5 to 2 mm, and the diameter is in the range of 1 to 10 μm. The material is platinum, tungsten or platinum-rhodium alloy. If a thin metal film (thickness less than 0.1 micron) is used instead of the metal wire, it is a hot film anemometer, which functions similarly to the hot wire, but is mostly used to measure the liquid flow rate. In addition to the ordinary single line type, it can also be a combined two-wire or three-wire type to measure the velocity component in all directions. The output electrical signal is amplified, compensated and digitized and input into the computer to improve the measurement accuracy, automatically complete the data post-processing process, and expand the speed measurement function, such as simultaneously completing the instantaneous value and the time average value, the combined speed and the sub-speed, the turbulence and Measurement of other turbulence parameters. Compared with the pitot tube, the anemometer [1] has a small probe volume, small interference to the flow field, fast response, and can measure unsteady flow rate; it can measure very low speed (such as as low as 0.3 m/s).
When a thermal probe is used in turbulent flow, airflow from all directions simultaneously impacts the thermal element, which can affect the accuracy of the measurement. When measured in turbulent flow, the temperature indicator of the thermal anemometer is often higher than that of the rotary probe. The above phenomenon can be observed during the pipeline measurement process. Depending on the design of the management pipe turbulence, it can occur even at low speeds. Therefore, the anemometer measurement process should be performed in the straight section of the pipe. The starting point of the straight line should be at least 10 × D (D = pipe diameter, in CM) before the measuring point; the end point is at least 4 × D behind the measuring point. The fluid section must not have any obstructions (angles, rehangs, objects, etc.).
product instructions:
1. Before using, observe whether the pointer of the meter refers to the zero point. If there is an offset, gently adjust the mechanical adjustment screw of the meter to return the pointer to zero point;
2. Put the correction switch in the off position
3. Insert the measuring rod plug into the socket, the measuring rod is placed vertically upwards, the screw plug is pressed tightly to seal the probe, the “correction switch” is placed at the full position, and the “full adjustment” knob is slowly adjusted to make the meter pointer full. Degree position
4. Set the “correction switch” to “zero position” and slowly adjust the “coarse adjustment” and “fine adjustment” two knobs so that the meter pointer points to the zero position.
5. After the above steps, gently pull the screw plug to expose the probe (the length can be selected according to the need), and make the red dot on the probe face the wind direction. According to the meter reading, check the calibration curve to find out. Measured wind speed;
6. After measuring a few points (about 10 minutes), the above steps 3 and 4 must be repeated to standardize the current in the meter. After the test, the “correction switch” should be placed in the off position.
Wind Sensor 