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685S Multiswitch Liquid Level Indicator for Atmospheric Vessels

The Model 685S Multiswitch is a liquid head pressure type control,
which continuously indicates the liquid level and supplies on and off signal as adjusted. Each switch may be set at different set points to control a separate device, such as an auxiliary or motor control relay, alarms, etc.


Liquid head pressure against a flexible elastomer diaphragm is transmitted directly to a leaf spring, which has a fixed pivot point at the upper end and an adjustable fulcrum point in the mid region of the leaf spring. For example, because 8’ of heavy liquid exerts more pressure on the diaphragm than 8’ of lighter liquid, the spring can be “stiffened” by moving the fulcrum down by the gravity adjustment knob (red), so the unit will still read 8’. The zero knob (green) moves the entire spring assembly and pointer, having the same effect as shifting the scale. The movement of the pointer rotates a linkage connected to a shaft extending into the explosion proof housing where the switches are located. The shaft drives a gear, which is connected to cams that actuate each switch individually.

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685S Multiswitch Liquid Level Indicator for Atmospheric Vessels


  • Easy to read: Scale reads the same as a hand tank gauge, making it unnecessary to convert psig of head pressure into feet and inches of liquid to get the correct reading.
  • Special Scales: Gallons, Pounds, Percent, etc. is available.
  • Long Life: All bearings are Teflon®, Delrin® or Moly Disulphide baked on Dry Film Lubricated Stainless Steel.
  • Weather Proof and Explosion Proof Housing.


  • Explosion Proof: CSA Approved: Class I, Group C & D Class II, Groups E, F and G hazardous locations.
  • Temperature: -20˚F to +225˚F Standard
  • Pressure: 0 to 4 ounces pressure (Atmospheric)
  • Range (Vessel Height): 3’ thru 60’ (see 685 code sheet).
  • Electrical Switches: SPDT Micro Switch, 11 Amp @ 130 or 250 VAC, 1/2 Amp @ 125 VDC, 1/4 Amp @ 250 VAC Induction
  • Electrical Connections: 1 /2″ Female Pipe Thread, 3 /4″ Female Pipe Thread (Optional)

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