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Insertion Turbine
Sight Flow Indicators
Calibration
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Flowmeter Calibration |
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Unless otherwise specified all of our flowmeters are calibrated on our
positive displacement oil or water flow rigs, these have an overall
uncertainty of ±0.25% (95% CL). The maximum flow range on
water is 190 litres per minute and on oil 40 litres per minute (depending
on viscosity). The flow rigs are checked annually against certified
weigh scales that are traceable to national standards, see rig calibration
certificate below.
Flow Rig Calibration Certificate The calibrators use a piston within a smooth bore tube to act as a moving barrier between the pressurising gas and the displaced test fluid. It generates a continuous train of electrical pulses by use of a linear encoder/translator attached to the piston. Each pulse represents an extremely small but very precise volume of fluid. The unit is virtually immune to the effect of the test fluids viscosity and density in accomplishing its volumetric flow determinations. The calibrator consists of a precision honed flow tube, a flow piston and shaft, a photoelectric sensor (encoder) associated valves, supply tank, and an electronic console to interpret and display the data. Air under pressure is introduced to the upstream side of the piston to provide fluid power for the calibration. Downstream of the piston the system is flooded and fully bled. The flow rate is controlled by the operation of the throttling valves. As the piston moves down the flow tube dispensing fluid in a precise manner through the flowmeter under test, it also moves the photoelectric sensor past the etched glass rule. The encoder produces an electrical pulse each time an etched line interrupts the light beam impinging on it. The frequency of the continuous pulse train produced by the calibrator during a run is proportional to piston velocity and thus to the flow rate of fluid dispensed from the tube. The total pulse count is directly proportional to the volume of fluid displaced by the piston. |
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