DMD Measurement Operating Principle

The ROOTS® Meter is designed to measure the volume of gasses and gas mixtures with a very high degree of accuracy. The time tested and accepted ROOTS Meter, with its permanent accuracy, employs the rotary positive displacement operating principle illustrated below. This built-in accuracy is fixed by precision, machined impellers and a rigid measuring chamber. Measurement is not affected by changes in gas specific gravity, pressure or widely flucuating flows. And unlike comparably rated diaphragm meters, the capacity of ROOTS Meters is not derated at elevated pressures. ROOTS Meters also offer differential testing capacity which reduces the need to shut down for testing and lowers future costs.

	Position 1: As the bottom impeller rotates in a counterclockwise direction towards the horizontal position, gas enters the space between the impeller and the cylinder.
	Position 2: At the horizontal position, a definite volume of gas in contained in the bottom compartment.
	Position 3: As the impeller continues to turn, the volume of gas is discharged.
	Position 4: Concurrently, the top impeller rotating in the opposite direction has closed to its horizontal position, confining another known and equal volume of gas. This process is repeated four times for each complete revolution of the impeller shafts. The flow of gas creates the rotation of the impellers.

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