Laminar flow element (LFE's)
calibration is a high accuracy job that few
flow calibration facilities can perform. The volumetric flow rate is determined by creating a pressure drop across a unique internal restriction, known as a Laminar Flow Element, and measuring differential pressure across it. The restriction is designed so that the gas molecules are forced to move in parallel paths along the entire length of the passage; hence Laminar (streamline) flow is established for the entire range of operation of the device. Unlike other flow measuring devices, in laminar flow meters the relationship between pressure drop and flow is linear.
Measurement Principle: Laminar Flow Elements embrace a system of minute parallel capillary passages. In each of this passages a laminar flow is established which produces a nearly linear relationship between the differential pressure and the flow rate. This effective differential pressure over the LFE is captured via a differential pressure transducer. First the actually passing volumetric flow rate through the Laminar Flow Element is evaluated, respecting the calibration data in combination with the actual gas state (medium, pressure, temperature and humidity at the
LFE). Then follows a conversion of this actual volumetric flow depending on the actual gas state to the mass flow. Last one can compute the
volumetric flow related to a specific gas state, generally the gas state under norm condition.
Laminar Flow Elements are factory calibrated mostly for air under norm condition at approx. 10 different flow rates. The standard calibration offers relative accuracy of better than 0.8 per cent of the real flow rate at the relevant point. This standard LFE calibration is effectuated with critical nozzles or reference devices and can be traced back to international standards. Special calibrations with a relative accuracy of better than 0.25 per cent are possible. An important advantage of Laminar Flow Elements is the fact that the physical 'frame value' zero (no differential pressure = no flow) can be determined with practically any wished precision and can be easily verified. The slight deviation to linear theory can be evaluated from the calibration data and is compensated through the S320 Controller program.
Our facility not only
has the capability to calibrate your laminar flow elements, but since we
build our own portable
flow standards and local leak
rate monitors, our experience isn't only in calibration!
We have calibrated laminar
flow elements manufactured by:
- Meriam Instruments
- Furness Controls
- CME Flowmeters
- Hastings Flow Products
- Alicat Scientific
If your manufacturer isn't listed
above, contact us with your product
information and we'll send you a quote!
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