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688 Level Switch for Pressure Vessels up to 2000 psig

The Model 688 is a single point on/off level switch, which completes an electrical circuit to a pump, valve, alarm or other devise. This unit senses virtually any liquid and does not need adjustment when the vessel contents are changed. It will ignore foam, surge or splash to indicate true liquid level, with repeatability to 0.050in. standard.


When liquid touches the sensor it starts a chain of activity throughout the sensors internal components, which in turn sends a signal to the circuit board inside the housing. A red LED is illuminated however if there is a sensor failure or other component failure, the relay will immediately transfer to the alarm condition.

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688 Level Switch for Pressure Vessels up to 2000 psig


  • Fail-Safe: Unit is field adjusted to high or low level fail-safe conditions.
  • Auto Test Self-Checking: The unique self-checking feedback loop constantly “proves” that the switch is working properly and offers superior reliability in critical applications.
  • Long Life: The all stainless steel, heavy-duty sensor resists damage from product abrasion or corrosion. No packing glands are used.
  • Explosion Proof: CSA Approved for Class I Group C & D, Class II Group E, F and G hazardous locations
  • Versatile Power Supply: The standard units are designed to accept 115 VAC, 230 VAC or low voltage AC or DC input power.


  • Electrical Housing: CSA Approved Class I, Groups C & D; Class II Groups E, F and G
  • Housing Operating Temperature: Ambient -20˚F to +160˚F
  • Operating Pressure: Up to 2000 psig
  • Sensor Operating Temperature: -20˚F to +220˚F
  • Electrical Input Voltage: Nominal: 115 VAC, 230 VAC, 24 VDC
  • Absolute Limits: 90-135 VAC, 180-270 VAC, +-4 VDC
  • Frequency: AC Power: 50-60 Hz
  • Time Delay: Independent, non-integrating on make and brake.
  • Delay Time Range: 50 milliseconds min., long delay, 30 sec. max.
  • Output: Relay DPDT Form C Contacts
  • Ratings: 5A @ 120 VAC Non-Inductive, 5 A @ 24 VDC Non-Inductive.

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