Introduction to the use of anemometer
1. Before use, observe whether the pointer of the ammeter points to the zero point. If there is any deviation, gently adjust the mechanical adjustment screw of the ammeter to make the pointer return to the zero point;
2. Put the correction switch in the off position;
3. Insert the plug of the measuring rod into the socket, place the measuring rod vertically upward, press the screw plug tightly to seal the probe, put the "calibration switch" at the full position, and slowly adjust the "full scale adjustment" knob so that the pointer of the meter points to the full scale. degree position;
4. Put the "calibration switch" at the "zero position", and slowly adjust the two knobs of "coarse adjustment" and "fine adjustment", so that the pointer of the ammeter points to the zero position
5. After the above steps, gently pull the screw plug to expose the probe of the measuring rod (the length can be selected according to the needs), and make the red point on the probe face the wind direction. According to the reading of the electric meter, check the calibration curve to find out Measured wind speed;
6. After measuring for several minutes (about 10 minutes), the above steps 3 and 4 must be repeated once to standardize the current in the meter
7. After the measurement, the "calibration switch" should be placed in the off position.
An anemometer is a speed measuring instrument that converts a flow velocity signal into an electrical signal, and can also measure fluid temperature or density. The principle is that a thin metal wire heated by electricity (called a hot wire) is placed in the airflow, the heat dissipation of the hot wire in the airflow is related to the flow velocity, and the heat dissipation causes the temperature change of the hot wire to cause a change in resistance, and the flow velocity signal is transformed into electric signal.
It has two working modes:
①Constant flow type. The current through the hot wire remains constant. When the temperature changes, the resistance of the hot wire changes, so the voltage across the two ends changes, thereby measuring the flow rate;
②Constant temperature type. The temperature of the hot wire is kept constant, such as 150°C, and the flow rate can be measured according to the required applied current. The constant temperature type is more widely used than the constant flow type. The length of the hot wire is generally in the range of 0.5-2 mm, the diameter is in the range of 1-10 microns, and the material is platinum, tungsten or platinum-rhodium alloy. If a very thin (thickness less than 0.1 micron) metal film is used instead of a metal wire, it is a hot film anemometer, which has a similar function to a hot wire, but it is mostly used to measure the flow rate of a liquid. In addition to the ordinary single-wire type, the hot wire can also be a combined double-wire or three-wire type to measure the velocity components in all directions. The electrical signal output from the hotline is input into the computer after amplification, compensation and digitization, which can 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 time average value, combined speed and partial speed, and turbulence. and other measurements of turbulence parameters. Compared with the pitot tube, the hot wire anemometer has the advantages of small probe volume, small interference to the flow field, fast response, and can measure unsteady flow velocity; can measure very low velocity (such as as low as 0.3 m/s).
