Positive Displacement Liquid Flow Calibrator
A Positive Displacement Liquid Calibrator (PDLC) is a volumetric-type measurement device, which measures the exact volume of fluid that passes through the flow meter under test while compensating for fluid viscosity and temperature. This allows for extremely high precision fluid flow measurement.
PDLCs are the most precise fluid calibrators available, with an uncertainty of ±0.05% of reading. The NIST fluid flow measurement laboratory uses this type of calibrator for their liquid flowmeter calibrations requiring high accuracy.
Features:
- NIST-traceable
- Printed, plotted calibration data
- Automated data acquisition
- 0.25% of reading accuracy
Positive Displacement Liquid Calibrators consist of a precision-honed and polished piston and cylinder assembly mechanically connected with a shaft to a linear encoder. The encoder side of the piston is pressurized with air to provide the force to move the piston. Calibration fluid is loaded into the opposite side of the piston, the meter under test, and a collection reservoir tank hydraulically located after a manifold of flow control valves.
The output from the encoder, temperature sensors, and the meter under test are directed through signal conditioning into a data collection and reduction computer, which uses Flow Dynamics' Windows-based "Flo-Cal" software.
Air pressure is supplied to the piston through a control valve and a pressure regulator. Once the pressure is applied, pressurizing the fluid, flow is created by opening one or more of the flow control valves on the downstream side to adjust the desired flow rate. Once the desired rate is established, the computer records all of the data variables into the "Flo-Cal" database.
When the piston reaches the end of the cylinder stroke, the flow stops. The air pressure on the encoder side of the piston is vented and air pressure is supplied to the collecting reservoir to provide motive force to return the piston to the starting point. As the fluid returns to the cylinder from the reservoir, it is directed through a filter to remove any minute particles that may be present in the line. A fluid diverting check valve prevents this fluid from passing backwards through the meter under test. When the piston reaches the starting position, the reservoir is vented and the piston is re-pressurized to restart the process.
Flow Dynamics has designed and manufactured many PDLCs per customer specification. In addition to new systems, we can retrofit an existing calibrator with all new electronics, computer software, and a new piston assembly. This allows customers to upgrade an older model calibrator to a high accuracy piece of test equipment for far less money than a brand new unit.