Sierra SL-800 instruction manual Initial Pressure Pulse Timing KPa Begins Ends

Outlet

Bypass Valve

Piston

Inlet

Figure 3 Basic Piston Prover

In real-world applications, there are significant dynamics to consider. At the beginning of a cycle, pressure rises rapidly until the piston accelerates to the speed of the flow stream. Figure 4 is an illustration of a typical Cal=Trak’s internal pressure during a measurement cycle. A near-maximum flow rate is illustrated to accentuate the pressure variations. The initial pressure pulse, lasting some tens of milliseconds, reaches a peak of about 0.5 kPa, or 0.5% of its working, near-atmospheric pressure. The pressure settles out to about 0.1 kPa (0.1% of working pressure) during the timed period. This pressure represents the added pressure due to the weight of the piston. Very small oscillations continue due to the piston’s under damped nature.

	0.8
			Initial Pressure Pulse
	0.6
	0.4					Timing				Timing
(kPa)
						Begins				Ends
	0.2
Pressure
	0
	0	100	200	300	400	500	600	700	800	900	1000
Intracell
	-0.2				M illiseconds
	-0.4
	-0.6
	-0.8

Figure 4 Cal=Trak Internal Pressure

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