1640系列 用于三位控制的微差压开关是在1630系列开关的基础上创新出来的微差压开关，它带有一个单刀双掷的浮动触点开关，能保持开关在一个中间位置。
示意图展示了工作原理：当隔膜被差压推动，它带动浮点开关在两个预设点产生动作，如果在预设点之间，开关没有任何动作。当差压升高到高预设点时，高位开关关闭，当差压降低到低预设点时，低位开关关闭。
典型的应用例子为马达驱动的风门，当风管中的静压增大到zui大预设点时，开关会控制驱动风门位置变化，当静压降低到zui小预设点时，开关也会驱动风门位置表话。如果采用皮托管配合使用，是一样的道理来控制风速，是供风管保持恒量供风。
注意：只能用于空气或其它兼容性气体。
Service: Air and non-combustible, compatible gases.
Wetted Materials: Consult factory.
Temperature Limits: -30 to 110°F (-34.4 to 43.3°C).
Pressure Limits: 10 psig (68.95 kPa) continuous, 25 psig (172.4 kPa) surge.
Switch Type: Single-pole double throw (SPDT) floating contact (not snap action).
Electrical Rating: Non-inductive: 2.5 A @ 110 VAC, 1.5 A @ 220 VAC, 1 A @ 24 VDC, 0.5 A @ 110 VAC; Inductive: 1 A @ 110 VAC, 0.5 A @ 220 VAC, 0.5 A @ 24 VDC. (De-rate 70-80% for very slow pressure changes.)
Electrical Connections: 3 screw type, common, normally open and normally closed.
Process Connections: 1/8" female NPT.
Mounting Orientation: Diaphragm in vertical position. Consult factory for other position orientations.
Set Point Adjustment: Screw type.
Weight: 4 lb 13 oz (2.18 kg).
Agency Approvals: CE.
