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Optomax Digital Range of Liquid Level Switches

Optomax Digital Liquid Level Switches Are Ideal For Applications With Restricted Space That Require A Miniature, Low Power And Low Cost Sensing Solution.

The microcontroller based sensor is solid state, incorporating an infra-red LED and phototransistor which are optically coupled by the tip when the sensor is in air. When the sensing tip is immersed in liquid, the infra-red light from the Optomax Digital sensor escapes making the output change state. The sensor can detect the presence or absence of almost any liquid type; oil or water based. It is insensitive to ambient light and is not affected by foam when in air or by small bubbles when in liquid.

The TTL compatible push-pull output can sink and source up to 100mA at a supply voltage range of 4.5 to 15.4Vdc and can be configured to output a high or low signal when in either a wet or dry state. A fail-safe PWM option is also available with a supply voltage range of 4.5 to 5.5Vdc.

With housing options for internal or external sensor mounting and for use in two operating temperature ranges; Standard (-25 to 80°C) or Extended (-40 to 125°C).

Available in two chemically resistant housing materials, Polysulfone, the standard choice for most applications or Trogamid, which is typically used in food and beverage applications.


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Part Numbering Guide


Supply Voltages (Vs) 4.5 to 15.4Vdc
or 4.5 to 5.5Vdc (PWM Output)
Supply Current (Is) 2.5mA max. (Vs = 15.4Vdc)
Output Sink and Source Current (Iout) 100mA
Operating Temperatures Standard: -25 to +80°C
or Extended: -40 to +125°C
(Above +85°C Trogamid is suitable for use in water based liquids, oil based liquids can cause deformation of the sensing tip and must be tested for compatibility)
Storage Temperatures Standard: -30 to +85°C
or Extended: -40 to +125°C
Housing Materials Polysulfone (Standard)
or Trogamid
Sensor Termination 24AWG, 250mm PTFE wires, 8mm tinned
Operating Pressures 0 to 20bar (M10x1 thread)
or 0 to 7bar (All other threads)


Sensor mounted from inside vessel (M10x1 thread)


Sensor mounted from outside vessel (M12x1,1/2″ SAE and 1/4″ NPT threads)



Output Voltage (Vout): Iout = 100mA
Output High Vout = Vs – 1.5V max
Output Low Vout = 0V + 0.5V max
PWM Output
Duty Cycle in Air 25% ± 10%
Duty Cycle in Liquid 75% ± 10%
Frequency 2kHz ± 10%


Wire Designation
Red Vs
Green Output*
Blue 0V

*See part numbering guide for output logic


  • Reverse polarity, ESD and transient over-voltage protected
  • Wide supply voltage range
  • Push-pull output, capable of sinking or sourcing up to 100mA, can directly drive small loads
  • Optional fail-safe PWM output
  • Standard and extended temperature ranges available
  • Polysulfone or Trogamid housing material options
  • Internal or external mounting options
  • High pressure option available


  • Solid state so no moving parts to cause unreliability
  • Small in size so they can be installed in applications where space is limited
  • Can detect tiny amounts of liquid when positioned correctly, ideal for leak detection
  • Fast response time
  • Repeatable switching point
  • Built-in output delays available on request for applications where sloshing causes intermittent switching
  • Very robust permitting use in a wide range of fluids and chemicals


Liquid sensing 001_450

When in air the infrared light is reflected back to the detector


Liquid sensing 002_450

When in liquid the infrared light is refracted and the output switches

  • This field is for validation purposes and should be left unchanged.