Different methods exist to transfer piston position into some form of readout. One method incorporates a ring type permanent magnet into the piston assembly. An external indication ring is magnetically coupled to the piston and indicates the flow rate on a scale. Because spring return, piston type meters do not rely on gravity to balance float position against fluid flow, they are not limited to a vertical mounting piston. As a result, they can be installed directly into vertical and horizontal lines.
Some units can monitor flow in a downward gravity feed line with an optional inverted flow scale.
And, unlike some flow sensor technologies, no flow straighteners or special piping are required. This principle of operation results in quick response, direct readout and no extra calculations or correction factors. They are compatible with oil and other petroleum based fluids, water based liquids, acids, air, compressed gases, corrosive and caustic fluids, liquid food products, paints and many chemicals. Since 1970, Hedland Flow Meters has supplied process flow technology equipment to the fluid power industry. To meet the ever increasing demands associated with this technology, Hedland Flow Meters has expanded their flow meter product line to include more than 7000 models of in-line, direct reading flow meters.