FAQs
What is a calibration?
By definition, calibration is the checking of a measuring instrument against an accurate standard to determine any deviation and correct for errors.
How does Otech calibrate anemometers?
At Otech, anemometers are calibrated by relating the raw output of the test anemometer to the reference wind speed measured by the Pitot-static tube system in the Otech wind tunnels. Calibration is normally performed over a range of wind speeds where a transfer function is generated using regression analysis.
Why do you need to calibrate anemometers?
A calibrated anemometer ensures that the instrument closely represents the measured wind speed. It also ensures that the wind speed measured by a calibrated anemometer is traceable to fundamental measurement quantities.
What is ISO 17025?
ISO 17025, more correctly defined as ISO/IEC 17025:2005, is the standard that defines the necessary requirements for developing a quality management system in test laboratories. Laboratories that are ISO/IEC 17025:2005 accredited ensure that test quality and traceability is maintained.
What is MEASNET?
MEASNET, Measuring Network of Wind Energy Institutes, is an international cooperation of measurement institutes whose goal is to provide quality measurement in the wind energy industry. Such measurement methods monitored by MEASNET members are anemometer calibration, turbine power performance, turbine noise emission, and turbine power quality.
Can Otech do a MEASNET test?
Otech can perform anemometer calibration procedures commonly done by MEASNET test laboratories. Otech is not currently a member, but is pursuing MEASNET membership.
What is uncertainty?
Uncertainty is the propagation of bias and random errors associated with a measured variable. In an Otech test or calibration report, uncertainties in the reference wind speed are reported as required by anemometer test standards.
What is your turnaround time?
Typically, for sensors most commonly tested at Otech, turnaround time is 2-3 days. For special testing, turnaround would depend on the complexity of the testing.
How much does a calibration cost?
The cost of a calibration depends on the type and number of anemometers to be tested and the type of test protocol to be performed. Please see quote request link for more information.
Are you NIST traceable?
Yes, all instruments used to measure the reference wind speed in the Otech wind tunnels are NIST traceable.
Is it necessary to perform post-calibrations after deployment in the field?
For wind energy applications, post-calibrations are recommended for cup anemometers deployed for turbine performance testing. According to IEC 61400-12-1, “The cup anemometer shall be calibrated before and recalibrated after the measurement campaign. The difference between the regression lines of calibration and recalibration shall be within +/- 0.1 m/s in the range 6 m/s to 12 m/s. Only the calibration before the measurement campaign shall be used for the performance test.”
With a post-calibration, one would have a better understanding of the consistency or the relative change in the sensor output after its deployment.
How often should you calibrate your sensors?
Calibration labs typically do not define how often a sensor should be calibrated (i.e. calibration intervals). This is determined by the end user through the investigation of specifications from the sensor manufacturer and of its use at the installation site.
“How often an item is used, the type of environment where it is used, and to what extent the user expects it to repeat measurements plays a major role in determining how often it requires calibration.”—Jay L. Bucher (ed), The Metrology Handbook (2004)
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