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Calibration of flow velocity measurement instruments – method

Calibrated instruments

The laboratory performs calibrations of both handheld and stationary instruments, including:

  • thermal anemometers
  • vane anemometers
  • cup anemometers
  • ultrasonic anemometers
  • pitot tubes with flow velocity reading
  • gravimetric dust anemometers combined with aspirating zero probes.

Calibration method

Calibrations are performed based on procedure P/01 “Procedure for calibrating anemometers”, which has been accredited by the Polish Centre for Accreditation.

The primary device for calibrating instruments for measuring local air velocity is an open-circuit wind tunnel. Airflow is generated by a fan with a motor and speed control system. The uniformity of the fan’s rotational speed is ensured throughout the range of airflow velocities.

An essential feature of the wind tunnel is its ability to maintain stable airflow in the measurement chamber in the range from 0.15 to 40 m/s. The basic instruments for measuring airflow velocity include a small velocity probe for velocities ranging from 0.15 to 1.5 m/s, and a static Pitot tube for velocities ranging from 1.5 to 40 m/s. An indirect method is used to measure airflow velocity in the measurement chamber of the tunnel, utilizing a multi-hole probe and a static Pitot tube. Electronic manometers with a resolution of 0.001 mbar, having a calibration certificate issued by an accredited laboratory or NMI, are used to measure differential pressure on the tube and the measurement probe.

An electronic barometer and an Assmann psychrometer are used to determine the current air density. The tunnel is located in an air-conditioned room with stabilized air temperature.