thermocouple for multi point measurement, submerged

[picante]

Hi, I'm struggling finding the right type of thermocouple.

I need to get water temperature at multiple locations of a water enclosure.

The enclose will not be under pressure.

Thinking of 4 sensors per layer, at 2-3 depths.

The issues that I have are:

The sensor and part of the cable needs to be submerged

I need to be able to fix the location of the sensor within the enclosure, ideally of the base of the enclosure, the depth will only be 15cm.

I would appreciate any suggestions.

Thanks.

[Henrik_Volkers]

SO the max temperature will be about 100°C.

Take whatever isolated TC, (or place a drop of 2K glue on the tip of a custom made TC cable, migth be overkill but think of the capilar effect, I have already seen a drowned Daqbox :))

with 100°C you can use common silicon to fix the TC or some standoffs (plastic pencil housing, or more fancy lab stuff). silicon works up to 120°C or more have a look at the datasheet 🙂

2K epoxi works nice, but is harder to remove.

Kepp about 10mm of the TC free in water. (For very stiff TCs 50mm) water is a very good heat conductor, so depending on the resolution you want to read, or what you want to measure (is the water stirred? ) the influence of your sensors should be minor.

Some more information about your task would be helpful. Looks like you want to measure the temp distibution while boiling eggs 😄

TCs are good for +-1K. if you want more differential resolution, place all you TCs close together in a stirred water bath ( together with a calibrated PT100) and do a custom calibration.

If you don't have a calibrated temperature sensor, you can get a clinical thermometer for a few bucks. these are calibrated to 0.1 at 38°C 🙂

[picante]

Thanks for your help again Hendrik.

Great tip around the custom calibration.

I have a small tank, I need to measure the temperature to understand how the tank water cools at diferent locations under some conditions.

Apologies, but I need to clarify a couple of things, my native language gets on the way sometimes and very new to this, but very keen to learn.

The measuring DAC specs show a 500VDC+ isolation, does the TC also need to be isolated.

The main concern now are what parts of the TC can be submerged in water. I'm not sure if I need to get TCs with special properties or modify the TC or its cable for this project to make them suitable.

I understand that the pencil casing will help with different heights, great idea, but is the only purpose of this pencil case? or is thermal or electrical insulation also the intention. Can I run part of the cable of the TC in the water?

I hope it was not your own Dacbox that got damaged but how does a drop of 2k glue help with the capilar effect?

Can you confirm for me please, the temperature sensing location of a TC is the very tip right?

Thanks again Hendrik.

[Henrik_Volkers]

Do you already have some TCs you want to use?

Here is a quick pic of what I mean

:

You can buy TC completely shielded/isolated, or cheaper with a blank visible pill (tip junction) as twisted pair.

Depending the number and thickness of your TCs you add a heat path to the outside.

The TC will always report the temperature it feels, which might or might not be the temperature of interest 😄

[picante]

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[picante]

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[picante]

Hi again,

I have not bought them yet.

Nice drawing, that's exactly the scenario that I have in mind.

If I understand correctly, I need to have the TC insulated and shielded right?

and if i wanted to go for smaller sensors, I should get the twisted tip type but the pill on the tip of these might act add an insulator?

Thanks Henrik.