Help! I can't use an underwater ultrasonic sensor.

Other Hardware Sensors
1

There is a problem in the school class to make an instrument for measuring distance in water using ultrasonic sensors using Arduino.

I bought an underwater ultrasonic transducer called TD1000KA, but I could not connect to Arduino because there was no circuit.

So, the general Aduno ultrasonic sensor, HC-SR04, is not coated with waterproof coating.

When I bought the JSN-SR04T 2.0 waterproof ultrasonic sensor, I found the distance from the air.

Under water, only the minimum measuring distance is printed out continuously.

Why is it not possible to use underwater waterproof product ....?

Is it because the ultrasonic voltage is only 5V and the ultrasonic intensity is weak?

Please help me

2

Why is it not possible to use underwater waterproof product ....?

Waterproof doesn't mean you can use it under water. It just means that it can be put under water without destroying it. Sonic distance sensors that are made for under-water use are usually called sonar but you'll find more on the internet if you use the search term "boat depth sensor".

Is it because the ultrasonic voltage is only 5V and the ultrasonic intensity is weak?

No, it's because these sensors are made to sense the first non-gaseous material in the beam direction. In your test it's the water. These sensors are often used to measure the liquid level in a tank, so they must handle liquid as an object.

3

Ultrasonic transducers intended for underwater ranging require sophisticated, high frequency and high voltage (typically 200V) electronics to operate. Ultrasonic transducers intended for air don't work underwater.

Without the appropriate circuitry, this project is not suited for Arduino. Very bad classroom project!

4

Notwithstanding the difficulties previously mentioned, there are some reports of success using ultrasonic distance sensors (intended for use in air) to measure distances under water:

"Seawolf" describes using an ultrasonic sensor for underwater depth sensing: "Preliminary results in the swimming pool show that it can measure from 4 to 12 feet pretty accurately."

"Admin" in this link and this one describes success with a waterproofed MaxBotix sensor: "The home-waterproofed MaxSonar that I did worked really really well. I tested it in a large cylindrical nuclear test plant vat of water that's 50 feet deep and 50 feet diameter (5 stories both directions). The MaxSonar was able to "see" the entire tank. "

This paper describes apparently successful use of a MaxBotix product as an underwater distance sensor.

MaxBotix has a page that talks about some of the challenges related to using their sensors underwater.

And this one seems to suggest success as well.

5

there are some reports of success using ultrasonic distance sensors (intended for use in air) to measure distances under water

Hope springs eternal in the human breast.

6

Well, here's yet another example where an ultrasonic distance sensor intended for air was successfully used to measure water depth: https://coconutpi.wordpress.com/ The section "Depth and Obstacle Detection" contains this image:

Image title "Our $US99 MaxBotix MB7078 in a waterproof housing interfaced with a TTL-RS232 Convertor and connected to an Arduino Uno"

And their test results:

The slope of the fitted line is "...4.17 which was close to the theoretical gradient of 4.31 (by dividing speed of sound in water by speed of sound in air both at 30 degrees celsius)"

Still not convinced?

7

kimhee:
Under water, only the minimum measuring distance is printed out continuously.

What water depth were you trying to measure?

8

Still not convinced?

I'm not surprised that with a lot of fiddling and kludging such sensors might be made to work, a little bit. Sort of like using a radio transmitter without any antenna.

The last image you posted showed an incredibly clumsy sensor, in a mason jar with thumbprinted plasticine seals, possibly recording depth measurements of 160 cm. How is that useful?

What is the point, when you can buy a sensor, for less than the cost of the Maxbotix, but designed and well suited for the task?

9

In this other thread, I was ready to believe the seemingly plausible assertion that "For ultrasonic transmission to work in water, you must use a transducer designed for working in water. They are quite expensive," and I hoped that the OP of that thread would do the tests I recommended, to prove the point, one way or the other.

He or she didn't do those tests, but it turns out that at least four others have, so there is good evidence that some ultrasonic transducers intended for air do, in fact, work underwater.

And, judging from some of the hobbyist's enthusiastic comments, they work well enough for their purposes.

Also, the CoconutPi kids measured depths up to 7 meters, not 160 cm. That, and the 50 feet claimed by one of the other experimenters, seems in the realm of "useful," but of course what is "useful" depends on one's goals.

And, if a $15 JSN-SR04T will do the job for some hobbyist, great. (As you noted, the only example using that particular sensor underwater was not entirely persuasive, and it would be interesting if someone, like the OP of this thread, could corroborate the findings...his/her current "0" could be because of too shallow depth.)

The one true sonar sensor you've identified lately (that I've noticed) is the "Airmar DST800 underwater transducer (cost about $270)" used in the cool Sea Renderer project that you mentioned. Which other sensor, costing less than the $99 MaxBotix and easy to use with the Arduino, did you have in mind?

10

Why not do the experiments yourself, and make a genuinely useful contribution?

I'm not interested in pursuing this pointless discussion.

11

Before you go: which other sensor, costing less than the $99 MaxBotix and easy to use with the Arduino, did you have in mind when you said "...a sensor, for less than the cost of the Maxbotix, but designed and well-suited for the task?"

12

Google will be happy to demonstrate that commercial underwater transducers are available for $30 or less on Alibaba.

Here is an idea: pot a simple piezo disk in silicone sealant -- guaranteed to "work" under water. But well enough to be useful?

13

jremington:
Google will be happy to demonstrate that commercial underwater transducers are available for $30 or less on Alibaba.

Yes, similar to the TD1000KA in the original post. For which, I understand, sophisticated high frequency and high voltage electronics are needed to operate.

14

kimhee:
When I bought the JSN-SR04T 2.0 waterproof ultrasonic sensor, I found the distance from the air.

Under water, only the minimum measuring distance is printed out continuously.

When you tested the JSN-SR04T under water, what distance were you trying to measure?