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Ultrasonic sensor cable length

Discussion in 'Sensors and Actuators' started by CXgamer, Aug 26, 2021.

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  1. CXgamer

    CXgamer

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    0
    Nov 12, 2017
    Hello all,

    I'm trying to measure the water level in my rain water collection vessel. The challenge is that it's 17 meters from the vessel to my electronics cabinet.

    I've tried an ultrasonic Arduino solution, which worked great out of the box. But after I've lengthened the cable to match my set up, the echo signal gets too distorted and is no longer detected.

    Pressure sensors also exist, but are quite expensive as far as I've seen.

    Maybe I can lower two rods in the water and measure its resistance? Not sure why I don't see this technique in the industrial water level measurement industry.

    Looking if anyone has some suggestions, open to new ideas!
     
  2. bertus

    bertus Moderator

    2,062
    777
    Nov 8, 2019
    Hello,

    Wich ultrasonic sensor are you using?
    What kind of cable are you using?
    Could conversion at the vessel help, before sending it over the cable?

    Bertus
     
    davenn likes this.
  3. CXgamer

    CXgamer

    8
    0
    Nov 12, 2017
    Hey Bertus,

    Thanks for your response!

    I'm using this setup (the JSN-SR04T sensor):
    https://www.makerguides.com/jsn-sr04t-arduino-tutorial/

    The cable to the sensor is a very thin Coax, which I've lengthened with an XLR cable, which is very shielded.

    Conversion at the vessel might help, haven't tested that yet (gonna need to order a new cable I think). I'd prefer if I wouldn't have to put electronics in there, since the vessel is going to be partly buried and not very accessible afterwards. It's a very humid environment in there, so I'm worried about possible corrosion as well.
     
  4. bertus

    bertus Moderator

    2,062
    777
    Nov 8, 2019
    Hello,

    The cable between the sensor and the board can likley not be changed.
    The add tells me that the sensor cable is 2.5 Meters.
    You could use the XRL cable between the board and the arduino and keep the sensor cable as origenal.

    Bertus
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

    11,702
    2,717
    Nov 17, 2011
    Over 17 m length a cable, even a shielded one, can pick up a lot of electromagnetic noise. Aso the 5 V TTL level from the Arduino is likely to drop across the length of the cable and signals may not be recognized with confidence by the sensor module and vice versa.
    Two options:
    1. Put the Arduino in a waterproof box near the sensor (using the supplied cable, max. distance 2.5 m), then use an RS232 converter to transmit the processed data from the Arduino to a computer at the receiving end (17 m away). RS232 is suitable for that distance.
    2. You could "abuse" 2 standard RS232 transmitters to improve signal to noise ration over the 17 m of cable like so:
      upload_2021-8-27_7-8-20.png
      RS232 converters come as modules or build one using one of the many MAX232 look-alike chips.
      Note that I added an additional power supply buffer capacitor on the sensor board. This may improve the stability of the sensor by dampening voltage drops along the length of the cable when short pulses of current are drawn by the ultrasound transducer.
     
  6. Bluejets

    Bluejets

    5,037
    1,052
    Oct 5, 2014
    Nrf24l01+pa+lna will work over that distance.
    Possibly even the NRF24L01.......
     
  7. CXgamer

    CXgamer

    8
    0
    Nov 12, 2017
    Thanks for the suggestions guys! I would like to keep putting electronics inside my vessel as a last resort option, since it's going to be hard accessing it afterwards. But I definitely like the RS232 technique, specially the first one seems resilient if I get a decent cable.

    The wireless protocols won't work, since the destination is underground, behind 30 cm reinforced concrete and 10 cm insulation.

    Random thought, would this work? Measuring the resistance of the water ought to be matching how much of electric rods are covered. Or am I being daft? The rods must be something that doesn't rust in water though.
     

    Attached Files:

  8. Bluejets

    Bluejets

    5,037
    1,052
    Oct 5, 2014
    Usually a good move to inform people of things like this in the beginning.
    Otherwise it sounds like you are making it up as you go.

    As for probes, electrolysis is a problem.
    There are ways to overcome it but you will need to do some footwork to find solutions.

    A float with a string wrapped around a potentiometer shaft is about as KISS as one can get.
     
    davenn likes this.
  9. CXgamer

    CXgamer

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    Nov 12, 2017
    My apologies.

    I didn't want to overload with specs and demands, or for you guys to work out something concrete. Was mainly aiming for loose ideas and suggestions that I didn't think about. Didn't mean for you to spend a great amount of time into this. Sorry that I wasn't clear about this earlier.

    To elaborate with details some more;
    • The vessel is outside, the electronics closet inside my basement. I get zero cellphone reception there and WiFi is easily blocked behind any of these walls.
    • The distance is about 10 meters outside, 7 meters inside.
    • The cable tray I'm planning to use also hosts my heat exchanger (8.6 kW), so there's prone to be interference. If a decent RS232, I'll route it differently.
    • The aim is to get it hooked up with HomeAssistant.
    • There's also a 4-20 mA or 0-10V water pressure sensor, but that's quite expensive (€ ~350)
    • There's also a KNX integrated water level sensor on its own, but the cable is 10 meters. The manufacturer is not sure if the signal will come through. The device is too expensive for me to experiment this on without knowing it works first.
    • The vessel is getting a shaft extension soon and the surroundings filled with dirt. I'll barely be able to reach the sensor with my arm.
     
  10. Bluejets

    Bluejets

    5,037
    1,052
    Oct 5, 2014
    How about a plastic tube run to the tank with a pressure switch and all your electronics inside and isolated from those interference prone utilities.
     
  11. davenn

    davenn Moderator

    13,883
    1,964
    Sep 5, 2009

    so put the wifi antenna on a cable so that it is outside the basement
     
  12. CXgamer

    CXgamer

    8
    0
    Nov 12, 2017
    This is a great idea! I'm trying this first! Thanks! :D
     
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