AnsweredAssumed Answered

ADT7420 for measuring water temperature?

Question asked by Space on Oct 29, 2015
Latest reply on Nov 16, 2015 by Lluis

Dear support,

I want to use ADT7420 to accurately measure water temperature with shortest
response time possible. I insulated the wire connections with epoxy so only the
top plastic case of the sensor was exposed to water.

I had it submerged in water for several days working fine, after that I did a
lab calibration tests in water bath going from 10C to 20 C to 30C and then it
started behaving strangely, randomly some measurements from 4Hz readout were 0C
and after few minutes a longer period of 0C ... then again working fine and now
again having some of these errors... when I put a hot soldering iron on top of
it it starts working fine again ...

Raw 4Hz readout output:
Screen Shot 2015-10-28 at 6.54.38 PM.png

Error suspect:
I know that the plastics for these casings are usually porous to humidity and
water so I suppose I damaged it with water? but now I read in your Q&A file:
"The sensors are very robust and do not suffer from moisture ingress issues,
unlike other sensors."

Can you tell me more about it - how water tight they really are? or how do you
achieve no moisture ingress? and can they be submerged in water for longer periods?

and what is the recommended procedure for impregnation without affecting too much the
response time (I'm thinking of dry vacuum impregnation with epoxy?). I bought
several more of your sensors so I'm about to start experimenting again before
we decide to use it for production.
Do you think that moisture ingress is the root of my problem?

Thank you very much for all your answers and support,