All-metal variable area flow switch with low set point and low pressure drop

All-metal flow switch for applications needing a very low switching threshold together with low pressure loss even at high flow rates. The switch point is about 1 l/min on falling flow, while the instrument handles flows up to 100 l/min of water. The body is brass or stainless steel with a G 1 female connection.

Features

• Set point range 1…100 l/min of water
• Switch point approx. 1 l/min on falling flow
• G 1 female connection
• Maximum pressure 250 bar (brass) or 350 bar (stainless steel)
• Maximum temperature 100 °C
• Accuracy ±5 % of full scale
• Reed switch in a sliding protective housing

Operating principle

An orifice float with an integral ring magnet moves inside a cylindrical tube in the direction of flow, opposed by the field of a fixed magnet at the top of the instrument. The float's field actuates a reed switch mounted externally in a sliding housing. The shape of float and tube means that a minimal flow is enough to lift the float and close the contact. When the float reaches the end of its travel, an additional flow passage opens, so higher flow rates do not cause a significant increase in pressure drop.