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Description: The SST Liquid Level Sensor provides single point liquid detection via a TTL compatible push/pull output. This optical liquid level sensor features a miniature design that allows for installation in areas where space is limited. Thanks to its minimal solid state design, this sensor has been built without moving or mechanical parts that can be jammed and stop working.

An infra-red LED and phototransistor accurately positioned at the base of the sensing tip ensure good optical coupling between the two when the sensor is in air. When the sensing tip is immersed in liquid, the infra-red light escapes from the cone, causing a change in the amount of light present at the phototransistor, which makes the output change state.


  • Supply Voltage: +4.5 Vdc to +15.4Vdc
  • Output Current: 100mA
  • Temperature Range: -25 to +80⁰C
  • Polysulphone Housing Tip
  • M12 threaded connector (mounted from outside)


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Customer Comments

  • You should mention that this sensor is on-off, either it’s in the liquid or it isn’t – it doesn’t give a level value.

    • Don’t be silly, this is definitely a liquid level sensor. It even has an integrated analog to digital converter with 1-bit resolution!

  • This looks entirely sealed, (i.e. there is no passage where the water interferes inside), so I presume it will work sideways? I have a side mount application….

    It would have been nice if you guys included the o-ring and nut sold by the manufacturer

  • To clarify a bit on the product. Think of this as an alternative to a standard float switch. There is a price difference there, but in most cases, it provides a more reliable way of sensing when a liquid has reached a certain point or level in the container it is in. Arbiag is correct, this won’t give you a variable reading.

  • The data sheet notes sensitivity to chlorine. I wonder if this would be suitable for a swimming pool. If it’s light-based, I presume changing daylight levels might skew readings a bit.

    • The data sheet mentions that chlorinated solvents will attack the material the sensor is made of. The minuscule amount of chlorine you find in pool water should not be an issue though. I have not tested this sensor so I can’t comment on daylight skewing the readings. It would probably be a good idea to keep this out of sunlight to ensure proper operation.

  • This is much more expensive than a standard moisture sensor that uses two probes and measures conductivity - does it provide something that those don’t? Also, if this sits in dirty water will it still work since the IR cone might be optically blocked?

  • So, if I intend to read the level of fuel in a deposit, I should use several sensors on a side mount, in order to obtain the variation during time. Is it correct? It sounds very good for the price!

  • Robert / last year / 1

    Could this be turned upside down and used as a rain sensor? Or would daylight confuse it?

  • I want a liquid level sensor that works with (near) boiling water. This one doesn’t fit as it is only suitable up to 80C. Even if it did I doubt it would last.. I’ve used an assortment of floats, pressure sensors, optical sensors, etc.. I’m currently using my own hybrid sensor (basically a resistance meter), while a lot better than anything I’ve been able to source so far, still has it’s limitations. So I’m curious if anyone else has a good idea?

    • Pretty sure this is what Keurig does to measure levels in the boiler (re: resistance meter). There are typically two small, metal rods that extend from the top of the boiler and point down towards the heating coil. I’d imagine their primary concerns were high temperatures and longevity, so it sounds like you’re on the right track.

Customer Reviews

2.3 out of 5

Based on 3 ratings:

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1 of 1 found this helpful:

Excellent liquid level sensor

Great experience using 50 (fifty) of these sensors for an electronics/computer education program. Water level sensing was a critical component of the program, and I tried several different technologies, including eTape and float sensors. I found no other sensors to be reliable. These sensors are compact, rugged, have no moving parts, and provide a simple interface. All 50 did exactly what they were supposed to do.

Too sensitive for me,

with just a drop of water on the end of it, it changes states. cost is to high as well.

Not worth Using

The Sensors form, small simple installation make it practical for limited space application, the issues was consistency. The singles it sends back jumps all over the place. It is supposed to be a simple high low switch but the data sheet says PWM, so I tried measuring pulse too but found the device gives faulty readings. I thought it was maybe a defective sensor so I tried a second one I had and same thing. Ended up having to use another method to detect coolant levels. Would not recommend using in any project that needs consistent results.

The issue may be occurring when liquid splashed up onto the sensor. I’d recommend contacting our tech support team. They should be able to figure out the best course of action.