HR-SR04 ultrasonic sensor and T3-LB

Hello Temco,

is it a way to use an ultrasonic sensor like this one with a high frequency pulse counter of a T3-LB ?
I don’t think so because the sensor frequency (10uS) is too high for the pulse counter of the T3 (100Hz), but I prefer to ask the question anyway.


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Yeah, the T3-XX series controllers can accept only up to 100 hz on the high speed inputs so you’d need to divide down the pulse with an Arduino or other board that can keep up to those pulse speeds. (Actually this 100hz is a conservative figure, they can handle up to around 1khz in lab testing here).

If you’re measuring fluid level in a tank by chance, you can have a look at these tank sensors, they output a 0 to 10k resistive signal that can tie directly into the T3-XX series controllers.

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Hi Maurice,

About tanks, I noticed that floaters (whatever their build) becomes stuck after time, mostly because the water inside the tank is not pure (far from it btw).
I thought about a resistive way to measure levels: if you put a metal sensor inside the water, the resistance changes when wet or dry.
Why not put a sensor inside the water for reference and measure the resistance between the “floater” and the reference ?
You set the sensor in T3-XX as a temperature sensor to measure a resistance (even if the result is set as degrees). If the resistance decreases, that means the sensor is submerged into the water (thus a level is reached).

Btw, how do you measure the resistance in T3-XX with your tank level sensor ? Custom measure ?

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Measuring the resistance of the water will not be a practical way to measure liquid level, there’s too many variables at play. The tank level sensor on our site is more for clean liquids, you are right, but I see no reason they wouldn’t work in a slightly dirty environment like a sump. Add a few program lines and a variable to store the state of the level sensor, watch for no changes in water level over a certain period of time and generate an alarm “Tank Sensor alarm, no fluid level change for XX days, please check the sensor”.

For an extra layer of safety you could wire one of the usual sump pump controller floats as a high level alarm, we could add them to our lineup if you’re interested.

Our analog tank sensor is a normal gas tank sensor but modified slightly to operate over a 10k ohm range which as you know, you can wire directly into the T3 controller with no external circuitry required.

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Yep, I made some tests and the resistance of water varies greatly with the quality of water. A little bit salty and it varies a lot…
About your tank level sensor, how do you measure the resistance (the chart in the product pdf) with a T3, and not just an ohmmeter ? a 0-10K (option 33) resistive measurement ?

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I’m not at my PC just now but the general idea is you will set up a custom range. You can search around this forum for a detailed example. I’ll do an example for a tank sensor when I get back to the office.

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2 posts were split to a new topic: Fluid Level Sensor