Patented precision calibration

07.09.2020

Measuring accuracy relies on calibration. With the calibration rig AperCal, FLEXIM now offers for users of FLUXUS flowmeters the possibility to precisely calibrate their clamp-on ultrasonic transducers autonomously at their sites.

Commonly, calibration consists of a comparison of the device under test (DUT) with a reference measuring instrument. Accordingly, the calibration of flowmeters is usually done on a wet flow calibration rig. But the flow profile in every flow rig is influenced by pipe characteristics and installation conditions, leading to an increased measuring uncertainty.

AperCal stands for aperture calibration. The patented, PTB and NIST traceable certified method eliminates those uncertainties by funding the calibration process on the basics of clamp-on ultrasonic flow measurement according to the transit-time principle: When an ultrasonic signal is emitted through a flowing medium, it gets carried by the flow and experiences a spatial shift. This shift results in a change of the signal path length and therefore in a difference of the transit time.

AperCal produces the same effect without flow through defined displacement of the transducers. This reduces the calibration procedure to the measurement of length and time. Both can be performed with extreme precision. And this results in an extremely accurate calibration and one that is not influenced by pipe or installation characteristics. 

The calibration process is simple and fast. There is no need to pump tons of water around. One trained person is sufficient to execute the computer-controlled operation.