Manufacturer: Industrial Measurements & Controls
Description/Function of unit
The PDQ meter consists of two basic units: The hydraulic flow measuring unit (FMU) and the electronic readout/control unit (RCU interconnected with oil resistant cables.
The precision metering cylinder designed for high pressure (3000 or 5000 PSIG) operation. A special four way flow-reversing valve ensures continuous monitoring and measurement. The fluid path through the unit limits the pressure drop to a near-zero level…even at maximum rated flow. Within the FMU, flow is converted to electric signals by our special linear velocity transducer.
The four valve reverse the flow path in the cylinder as the piston approaches the limit of its stroke in either direction. Operating power for the valve is provided by low pressure shop air (40-60 PSIG). Valve reversal time is approximately 0.1 second and except for this momentary interval, the valve remains in a dormant condition. The "open center" valve design ensures unrestricted flow during valve reversals. When the four way valve operates, the piston reverses, the flow signal is held at its existing level, and the velocity transducer signal polarity reverse. The signal flow is directly proportional to instantaneous volumetric flow sensed. This signal is also available in analog from at a convenient front panel connector. This makes it easy to use external instruments… oscilloscope, strip chart recorder, X-Y recorder, or power amplifiers for servo control…or even am on-line computer. High dynamic fidelity means that the flow signal can be used for transient as well as static measurement and for monitoring or feedback control of time-varying flow superimposed upon static flow.
Automatic Model: In the "Automatic Mode" the logic circuits provide a valve reversal signal each time the piston nears the end of a stroke.
Dynamic Signal Mode: Operation in the "Dynamic Signal Mode" is identical to the automatic mode except that the low pass filter in the signal circuit is reduced.
Calibrate Mode: In the "Calibrate Mode" PDQ meter operation is non-cycling and the low pass filter is connected in the signal circuit.
Manual Mode: The "Manual Mode" is non-cycling identical to the calibrate mode except that the low pass filter in the signal circuit is bypassed and the digital meter does not "hold" the existing reading at the end of the single stroke. The manual mode is especially useful for studying transient behavior or to observe flow response resulting from a change in the hydraulic system under test.