Saltwater Arduino Water Temp sensor

[ian5142]

Hello all,
I am looking at getting a relatively cheap saltwater capable water temp sensor to feed into my Ardunio, that feeds OpenCPN, currently heading, pitch and roll.

I was looking at get a DS18B20, but it doesn't specifically mention salt water. https://www.aliexpress.com/item/1005004412646322.html

I am looking to spend less than $60. The plan is actually to mount the thing inside the saltwater intake filter for the wet exhaust, the seaweed collector if you will.

Thanks

[flightlead404]

I would look at the sensors being used to automate home saltwater aquaria. I'm sure there are Arduino or similar projects for that.

What are you trying to accomplish?

Trying to see if its warm enought to swim? Or what the temp differential is from the hot to the cold side of the exhaust for some reason?

Perhaps there's a better way.

[ian5142]

No, nothing that detailed. We run a boat tour and often get asked what the water temperature is.

[Captn Caveman]

That one would work fine. It is a resistance type or RTD sensor, the stainless housing is just for protection and as a heatsink, the actual sensing element is a thin film or wire assembly inside the housing. The saltwater environment should have no effect on the readings. There are also ceramic housing RTDs available if you didn't want to worry about corrosion at all; I know Honeywell makes one but it is much more expensive ($40 on digikey for a 1-off buy).

[Ryban]

I think the DS18B20 sensors will work fine as well -- the ones with stainless steel encapsulations. You may want to beef-up the water proofing where the cable enters the stainless housing. They're very cheap at least. If it's a permanent installation, I'd probably cast it into a thin cylinder of epoxy.

You could also use it with the SensESP library or similar if you want to send data over WiFi to your SignalK server (if running).

[rooiedirk]

Just take a cheap sensor and mount it somewhere against the inside of the hull.(below the waterline) A little (temp) insulation over it and you will measure the outside water temp.

[SV-Apres]

I have a few DS18B20's for various things including:

• Raw water intake - the sensor is cable tied directly to the raw water intake
• Mixing Elbow - the sensor is hose clamped to the mixing elbow

these are connected to a couple of ESP32's running Sensesp. one of the code examples can be found here:

https://github.com/Techstyleuk/sensesp-engine_monitor

you should be able to cherry pick the code from here and there is a video that explains it here:

https://youtu.be/Zay2ALtgxzc?si=TQOXpyVA7BRMMYXs

easily be able to do it for $60

[Zanshin]

The DS18B20s are what you want. They sensor head is already waterproof, but the 3 pins coming out are not. You can solder wires to the 3 pins and then "pot" it yourself, or buy the available steel housings. The sensors are fast and quite accurate. There are lots of available libraries as well (including one I wrote )