Laser optical flow measurement
On-site calibration of flow sensorsacc. to ISO/IEC 17025
Application areas
- Transparent fluids (e. g. drinking water, pre-cleaned sewage, long-distance heating, district cooling)
- Cast and steel pipes with dimensions ranging from DN 150 up to ca. DN 1000 and PN 25 (40)
- Undisturbed inlet length of at least 5 to 10 D and
- Fluid temperatures up to Tmax = 180°C.
Measurement uncertainty – in practice
The actual measurement uncertainty of the calibration depends on the on-site flow conditions. Hence the position of the ball valve in regards to the flow situation is critical and must be chosen well. For the characterization of the flow conditions, we developed a key coefficient modell resulting in five velocity profile classes. The following table shows the achievable measurement uncertainties for each one of these profile classes. These numbers are based on the measured value with a coverage factor of k = 2 for resulting 95 % confidence interval.
Our experience
Until 2021 more than 200 flow sensors of district-heating and drink water supply were calibrated on-site. One third of the calibrated flow sensors showed a significant or rather high measurement error. These numbers confirm the benefits of the on-site calibration method for flow sensors.
