Added to our calibration capabilities: calibration certificate on wind-direction. As we receive more and more request for not only wind-speed calibration but also for a calibration certificate on wind-direction, we have invested in this possibility. We can generate several calibration reports as a standard: starting from a 4 point calibration (per 90°), up to a 24 points calibration (per 15°). As a standard we make the calibration at a constant wind-speed of 10m/sec but we are flexible in following any request if necessary. This service can be provided for our 2D and 3D ultrasonic anemometer series, but also on our (Cup &) Vane types. No need to mention that this is available both for first initial calibration as well as for re-calibration of all models. Just to make you aware of the fact that Delta OHM’s ISO17025 accredit calibration lab for wind speed (air speed) is a real serious business: in this laboratory we operate 2 wind tunnels. Both are Göttinger-Type, circular tunnels with a closed circuit. One tunnel we use for low range calibrations in the range of 0,15m/sec to 35m/sec. This tunnel has a circular test section of 320mm. The other tunnel is used for high range calibrations, typically from 1m/sec to 65m/sec.
The reference standard that is being used in both tunnels is LDA. Laser Doppler Anemometry is a measurement technique that is based on laser light scattering without the need of having a physical contact with the flow. By using 2 laser beams that are focused in a certain way, it provides a high accurate measurement with a very high resolution.
When an instrument is calibrated, it is placed in the full airflow that is generated by the wind tunnel. In the picture below a typical set-up for measuring one of the Delta OHM ultrasonic wind sensors is displayed. To make sure that wind from all sides is being measured within the specifications, it is necessary to slowly rotate the instrument during the calibration procedure. Only in this way we can issue a calibration report, stating that the instrument is fully within specifications.