I am using the above said HC-SR04 ultrasonic sensor with Arduino pro mini. Till now, able to get the range working properly.
My plan is to use this in the overhead tank to measure the quantity of the water present in the tank. My worry is that, the sensor will be facing the water vapour all the time as shown in the figure (Not actually my setup but close one).
enter image description here

  1. How can i protect the sensor from the vapors?
    I have conformal coating option but seriously i have no idea still about reaction of the sensor for the same. I could still protect rest of the circuitry.
  2. Whether the water vapor affect the measurement and behavior of the sensor?
  • \$\begingroup\$ Spray it with some silicone grease or WD40, you want a protective layer that won't interfere too much with the sensor, a plastic sheet will probably cause some reflections and I don't know what a hard coat of conformal would do. But seeing as these sensors are dirt cheap, maybe try a few methods and see if the sensors still work, got with the method that doesn't interfere too much with the readings. (or just get some sealed ultrasonic sensors to replace the default ones on the board) \$\endgroup\$
    – Sam
    Commented Dec 22, 2016 at 22:43
  • \$\begingroup\$ @Sam they are dirt cheap.. I will try conformal coating soon after I receive many more samples and update here \$\endgroup\$
    – User323693
    Commented Dec 23, 2016 at 1:15
  • \$\begingroup\$ @Umar Can you keep the temperature of the sensor above the dew point (or above ambient for simplicity)? \$\endgroup\$ Commented Jan 24, 2019 at 11:00

1 Answer 1


Sorry for bumping up an old question but I'm in the same boat of requirement.

And to my surprise there are quite a few new sensors in town:

This one has 2 transducers instead of 1 therefore has less minimum detection distance as compared to JSN SR04T. It is also completely sealed and waterproof.


Before finalizing on this I had bought another one which was a waterproof modified version of HC-SR04 from here


The 1st one is much more rugged and waterproof as compared to the latter one.


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