Reef Discussion

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
Best Way To 'salt Water' Proof A Temperature Sensor
I am after some ideas about the best way to make a Temperature Sensor suitable for permanent exposure to salt water.

You can buy these ones at a reasonable price - they have a stainless cap on the end which I am guessing wouldn't last long in salt water.

afab.cba.mit.edu_classes_863.14_people_matthew_arbesfeld_img_final_final_temp_sensor.jpg



You can also buy them with a plastic cap, like this

acdn.sparkfun.com__assets_parts_6_4_1_2_11050_04.jpg


But they are 5 times+ the cost of the stainless steel ones.

If I melted some plastic and then dipped the stainless steel version into the plastic - would that work? Would the plastic retain it's pre-melted characteristics?
 

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
@Buddy , unfortunately that is an analogue sensor rather than the digital sensor that I need - I might be able to make it work, but would prefer not too.

But, they do something that I was thinking about.

They sell this
ai.ebayimg.com_00_s_ODAwWDgwMA___z_Md4AAOxycgVThYSY___57.JPG


But also sell this
ai.ebayimg.com_00_s_ODAwWDgwMA___z_zQAAAOxyaURThZAM___57.JPG


This one looks to be the same as the first but with some type of epoxy casing.

I had been thinking of finding a mould and using something like this
ai.ebayimg.com_00_s_NDg4WDUwMA___z_0m4AAOSwMmBVsJX____12.JPG


Or, what about encasing the probe in hot melt glue?
 

Sam Parker

Moderator
May 6, 2013
4,802
2,397
Geelong
Following along. I go through quite a few STC-1000's for people and it seems to be pot luck if they come with stainless or plastic probes.

Silicon would have too much temperature insulation. How about a glob of plasti-make around the sensor?
 
Sep 24, 2013
367
280
Palm Beach
In the past I simply dipped it in the silicon glue tube. It is quick but the finishing is not very good looking.
These days I wrap it in a heatsink and burn it with a lighter, to seal it.

Also, the metal tip last about an year, when in contact with saltwater, before they start rusting.
 
Sep 24, 2013
367
280
Palm Beach
I have tested the "Plasti dip" equivalent, from bunnings, on some aquarium related stuff, including the same temperature sensor and I wouldn't recommend it.
Its a bit laborious because it takes at least 4 coats to make it thick enough and at the end, it is very easy to pell off.
 

Andrew B

Member
Mar 14, 2015
618
189
Kangaroo Ground
My dad had some that was in a yellow container that was like a gooy paint that paint on with a brush. He used in when we went to the desert to repair stuff on the car and trailer. I think he got it from autobarn.
 
Sep 24, 2013
367
280
Palm Beach
I think plastimake would require some sort of glue, because it won't weld to the sensor's cable.
I have used it to build a couple of things like clam base and rock structure support. It sells for ~$10bucks 100g at Jaycar. Good stuff to have around.
 

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
These days I wrap it in a heatsink and burn it with a lighter, to seal it.
I had thought about that option, but I wasn't sure how I was going to make the end nice and neat - I like to make things look as professional as possible :rolleyes Pinching the end together was an option, or turning over the end like a parcel ...

But, then I found these
athumbs.ebaystatic.com_images_g_FkMAAOSwX_dWsw5V_s_l225.jpg

Adhesive heat shrink end caps :) Use some adhesive heat shrink over the stainless steel body, and then put one of these end caps over the end and it should look like a bought one :D

Now, I have received a quote overnight from a Chinese supplier at USD5 each for a plastic encapsulated sensor and a 3.5mm plug on the end, but I would need to buy 50 !!

Time to do some sums ...
 

MagicJ

Moderator
Jul 11, 2011
9,650
3,761
Hobart, Tasmania
@NiCd - don't get me looking at the Carbatec site :rage They have recently opened a new store in Hobart, and it will remind me that I need to spend $1k+ on a dust extraction system to go with my new table saw I bought a few months ago :p