Calibrating a hot-wire anemometer is an important step to ensure its measurement accuracy and reliability. Below is a basic calibration process, but please note that the specific calibration steps may vary depending on the model and manufacturer of the hot-wire anemometer. Calibrating a hot-wire anemometer is essential to ensure accurate air velocity measurements.
Maintenance of the hot-wire anemometer
- Do not use in a flammable gas environment: Hot-wire anemometer is strictly prohibited from being placed in a flammable gas environment during use, and the anemometer probe should be avoided in such environments to prevent fire or explosion accidents.
- Emergency treatment of abnormal situations: If the anemometer emits abnormal odor, sound, or smoke during use, or liquid flows into it, it should be turned off immediately and the battery removed to avoid the risk of electric shock, fire, or equipment damage.
- Waterproof treatment: Avoid exposing the probe and anemometer body to rain to prevent electric shock, fire, or personal injury.
- Do not touch the sensor: Do not touch the sensor inside the probe to keep it in good condition, and do not touch the sensor part of the probe when the anemometer is powered.
- Battery management: When the anemometer is not used for a long time, please remove the internal battery to prevent battery leakage and damage to the equipment.
General steps for calibration
Prepare calibration equipment
First, you need to prepare some basic calibration equipment, including:
- Standard wind speed source: For example, a calibrated fan or wind tunnel that can provide known wind speeds.
- Thermometer: Used to measure the ambient temperature, because the sensitivity of the hot-wire thermo anemometer may change with temperature.
- Stands and clamps: Used to fix the hot-wire anemometer and ensure it remains stable during measurements.
Set up the environment
Make sure the calibration environment is stable and avoid interference factors such as strong winds, vibrations, or temperature changes. If possible, calibration should be performed in a temperature-controlled laboratory environment.
Connect and preheat
Connect the hot-wire anemometer to the power supply and data acquisition system. Preheat according to the instructions in the equipment manual to ensure that the hot-wire sensor reaches a stable working state.
Measure airspeed at different points
- Set up airflow: Adjust the air speed in the test section to different known values. This can be done by setting a fixed speed in the wind tunnel or manually controlling the airflow.
- Record reference and hot-wire anemometer readings: At each airspeed, take measurements from a calibrated reference anemometer and the hot-wire anemometer. Make sure you record multiple values at different airspeeds within the expected range of the equipment.
Compare readings
- For each airflow condition, compare the readings from the hot-wire anemometer and the reference handheld anemometer.
- Calculate the deviation (error) of the hot-wire anemometer reading from the reference.
Zero calibration
In the absence of any wind speed, record the reading of the hot-wire anemometer. This reading should be close to zero or the zero offset value specified in the equipment manual. If the reading is off too much, a zero adjustment may be necessary.
Sensitivity calibration
Using a standard wind speed source, expose the hot-wire anemometer to a range of known wind speeds. At each wind speed point, record the hot-wire anemometer reading and compare it to the standard wind speed. Calculate the error and adjust the sensitivity setting of the equipment as needed.
If the hot wire anemometer has a temperature compensation function, it also needs to be calibrated at different temperatures to ensure that the device can measure accurately at different ambient temperatures.
Adjust the calibration curve
If the hotwire anemometer has a calibration adjustment feature (either through software or manually), use the collected data to adjust the anemometer. Typically, this involves plotting the reference velocity versus the hotwire velocity and adjusting the anemometer settings to minimize the error.
If adjustment is not possible, you can create a correction factor or calibration curve for future measurements. This curve accounts for any systematic errors or biases.
Verify the calibration
After calibration, test the anemometer again at multiple points to confirm the accuracy of the adjustments. If necessary, repeat the process to obtain consistent and accurate results.
Data Recording and Analysis
Record all calibration data, including measurements, standard values, errors, etc. for each wind speed point. Use data analysis tools (such as Excel or specialized calibration software) to evaluate the calibration results and determine if further adjustments are needed.
