Digital thermometer for diving?

[Pitlamp]

I have as Brannan digital thermometer I bought for hydrological purposes. I've looked at it, and with a bit of sealant I reckon it could be made reasonably waterproof. It only costs a few quid, so it's probably worth trying. I think the main problem would be reading the display underwater.

https://www.amazon.co.uk/Brannan-Thermometer-Traceable-Calibration-Certificate/dp/B09ZHZ5V8P

Thanks Langcliffe; yes Brannan is a good company; they sell excellent instruments.
The CDG's rain gauges ( https://cavedivinggroup.org.uk/visbot-public/ ) came from there in fact.

 

[alanw]

I recently saw this blog post: Taking A $15 Casio F91W 5,000 Meters Underwater. They filled a cheap watch with oil and strapped it to the arm of an ROV which then went down to almost 5000m. It kept on working. I wonder if the same could be done to a cheap aquarium thermometer like this on eBay for less than £6? WATERPROOF: With Sealed Ring Design, Aquarium Thermometer can completely submerge into the water

This Reddit post suggests "50cst MicroLubrol silicone", not readily available in the UK, however this, again from eBay for £7.45 might work.

 

[Cantclimbtom]

I recently saw this blog post: Taking A $15 Casio F91W 5,000 Meters Underwater. They filled a cheap watch with oil and strapped it to the arm of an ROV which then went down to almost 5000m. It kept on working. I wonder if the same could be done to a cheap aquarium thermometer like this on eBay for less than £6? WATERPROOF: With Sealed Ring Design, Aquarium Thermometer can completely submerge into the water

This Reddit post suggests "50cst MicroLubrol silicone", not readily available in the UK, however this, again from eBay for £7.45 might work.
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But wouldn't encapsulation in or filling with oil affect it's ability to respond in a timely manner as a thermometer?

 

[Pitlamp]

Interesting; some dive computers are oil-filled. I remember having lots of fun changing a battery in an Aladin Nitrox computer submerged in a bowl of paraffin oil. Saved a small fortune though - but after all the mess and mather I can see why dive shops charge so much to fit a battery!

I'm wondering if that device alanw flagged up would actually work without any tinkering? (Thanks by the way.) For the application we need it for the maximum depth it would have to withstand is only 5.6 m. At that price it might be worth a punt.

 

[ChrisB]

I'm wondering if that device alanw flagged up would actually work without any tinkering?

Minimal tinkering would just be to take it apart, which I assume is necessary to change the battery, and put silicone grease on the seals.