How are wind sensors calibrated?

Professional wind sensors are calibrated against traceable reference standards to establish how their readings compare with the reference, and with what uncertainty. That result is then used to verify that the sensor remains within its specified tolerances. Calibration may be carried out during manufacture and repeated periodically throughout the instrument’s life, depending on operational requirements and quality procedures. Many organisations choose UKAS-traceable calibration to provide documented evidence for quality management systems, audits and regulatory compliance.

What happens physically

The instrument is placed in a wind tunnel whose air speed is controlled and measured against a reference traceable to national standards. Readings are taken at a series of speeds across the range, and where direction is being verified, at a series of angles through 360 degrees.

The result is a certificate stating what the instrument read against what the reference read, the uncertainty of the comparison, and the conditions it was carried out under. Gill carries out traceable calibration in its own UKAS wind tunnel.

Calibration measures, it does not adjust

This is the part most often misunderstood. On an ultrasonic anemometer there is no adjustment to make. The measurement is a timing calculation across a fixed geometry, so there is no gain to trim and no zero to set, and nothing wears to pull it off.

Calibration therefore does one specific job: it establishes how the instrument reads against the reference, with a stated uncertainty. Checking that result against the instrument’s tolerance is verification, and the certificate is the evidence for it.

On a mechanical sensor the same exercise means something else, because bearing wear genuinely does move the response. There, periodic calibration is detecting drift. On an ultrasonic sensor it is confirming its absence.

Traceable, accredited and factory calibration

Traceable calibration is available across the WindObserver range and is standard on the Research range. The WindObserver IS has factory calibration traceable to national standards, but individual calibration certificates are not available for it, which is worth knowing before it is specified into a quality system.

Where UKAS accreditation comes from

Labcal is an independent UKAS-accredited calibration laboratory, Lab 0625, operating to ISO/IEC 17025:2017. It calibrates across gas and air flow, air velocity, liquid flow, pressure, temperature and humidity.

For environmental measurement that covers anemometers, Pitot tubes and thermal probes, alongside pressure gauges and transducers, thermometers, temperature and humidity probes and data loggers. Labcal supports equipment from Gill and other manufacturers, so a site with a mixed instrument list can consolidate rather than manage several laboratories.

What calibration does not tell you

• It does not validate the installation. A certificate proves the instrument was correct in a wind tunnel, not that it is correctly sited on your mast.
• It does not cover the data path. Scaling errors, protocol mismatches and logger configuration sit outside it and are a common source of wrong numbers.
• It is a point in time. It says the instrument was within tolerance on that date, which is why the interval matters.