The principle and application method of hot bulb anemometer
1. Construction principle
It is an instrument capable of measuring low wind speed, and its measurement range is 0.05-10m/s. It is composed of two parts: a thermal ball probe and a measuring instrument. The probe has a glass ball with a diameter of 0.6mm, and a nickel-chromium wire coil for heating the glass ball and two thermocouples connected in series are wound inside the ball. 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; on the contrary, 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).
2. How to use
① Before use, observe whether the pointer of the ammeter points to the zero point. If there is any deviation, you can gently adjust the mechanical adjustment screw of the ammeter to make the pointer return to the zero point;
②Place the correction switch in the OFF position;
③Insert the measuring rod plug 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-scale position, slowly adjust the "full-scale adjustment" knob, and make the meter pointer point to the full-scale position;
④Place the "calibration switch" in 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 meter, check the calibration curve to find out the measured wind speed;
⑥ After measuring for several minutes (about 10 minutes), the above ③ and ④ steps must be repeated once to standardize the current in the meter;
⑦After the test, the "calibration switch" should be placed in the off position.
3. Precautions
① This instrument is a relatively precise instrument, strictly guarded against collision and vibration, and cannot be used in places with excessive dust content or corrosiveness.
②The instrument is equipped with 4 batteries, which are divided into two groups, one group is three cells connected in series, and one group is single cell. When adjusting the "full scale adjustment" knob, if the ammeter cannot reach the full scale, it means that the single battery is exhausted; when adjusting the "coarse adjustment" and "fine adjustment" knobs, if the pointer of the ammeter cannot return to zero, it means that the three batteries are exhausted; when replacing the battery, open the small door at the bottom of the instrument and connect it in the correct direction.
③ After the instrument is repaired, it must be recalibrated.
