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  1. Technical support
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  3. Flow sensors

Calibration of flow sensors

ISO calibration flow (water)

The reference measurement of flow sensors for the measurement of liquids is done with a reference device.

During the reference measurement, the medium flows through the measuring instrument to be calibrated and another reference device that has been calibrated beforehand. Often, reference Coriolis flow meters are used, as their measuring principle allows them to measure a temperature- and pressure-independent mass flow rate, which results in them having very high ranges of accuracy.

The calibration is performed on the basis of 3 or 4 measurement points, which are distributed over the flow range. Usually, the calibration points are at 10%, 25%, 50% and 100% of the associated measuring range. As a rule, calibrations of water flow sensors end at a value of 600 l/min. This needs to be taken into account particularly for devices with higher measuring ranges. By default, the calibration is performed with factory settings using the analogue output (current) or, alternatively, visually using the display of the device or the analogue output (voltage).

ISO and DAkkS calibration flow (air)

The comparative measurement of compressed air meters is performed on the basis of critical nozzles.

During the calibration by means of supercritical pressures in de Laval nozzles, the measuring medium is drawn in at atmospheric conditions to accelerate the flow rate so that it reaches the speed of sound at the smallest diameter of the nozzle.When this critical flow condition is reached, the flow rate is limited to a constant value.

The calibration is performed on the basis of 6 measurement points, which are distributed over the flow range.As a rule, calibrations of compressed air and industrial gas meters end at a value of 700 Nm³/h. By default, the calibration is performed with factory settings using the analogue output (current) or, alternatively, visually using the display of the device or the analogue output (voltage).