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Optomax Digital Range of Liquid Level Switches

The Optomax Digital Range of 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 although these liquid level switches can be used in other applications.


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Part Numbering Guide


Supply Voltage (Vs)

Supply Current (Is)

Output Sink and Source Current (Iout)

Operating Temperatures

Storage Temperatures

Housing Materials

Sensor Termination

Operating Pressure

4.5 to 15.4Vdc
or 4.5 to 5.5Vdc (PWM Output)

2.5mA max. (Vs = 15.4Vdc)


Standard: -25 to +80°C
Extended: -40 to +125°C

Standard: -30⁰C to +85⁰C
Extended: -40⁰C to +125⁰C

Polysulfone (standard option) or Trogamid

24AWG, 250mm PTFE wires, 8mm tinned

0 to 7 bar


Optomax Digital Range of Liquid Level Switch thread inside drawing
Optomax Basic Liquid Level Switch drawing


Output Voltage (Vout)

Output High

Output Low

PWM Output

Duty Cycle in Air

Duty Cycle in Liquid


Iout = 100mA

Vout = Vs – 1.5V max

Vout = 0V + 0.5V max

25% ± 10%

75% ± 10%

2kHz ± 10%


Liquid Level Wiring Diagram









  • 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.