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Temp sensor failure, again

A project log for Solar water heater monitor

Monitor and log temperature of wood fire boosted Solar hot water heater

SaabmanSaabman 05/27/2019 at 12:463 Comments

I had previous written about a failure of the temp sensor submerged in the tank - damn ebay "water proof" sensors... After going through a couple of them after 6 months or so I finaly drilled a hole in the side of the tank covering and embedded a new sensor in through the insulation and next to the tank and sealed the hole - no more submerged sensor. Problem solved I thought, but alas the sensor has again failed I can only put it down to the constant extreme temperature has cooked the sensor - aledgedy the sensors are good for 125deg C but a constant 90degC or so is just too much for them. is this now a case of chinese knock off dallas sensors or they just cant handle the heat?

Discussions

Saabman wrote 05/27/2019 at 22:30 point

thanks for the tips I hadn’t thought about using an analog sensot - I’ve got some thermocouples and associated bits left over from my 3D printer build - the catch is I only have one ADC pin on the esp8266 which is already been used. But the whole board needs a redesign anyway so might just multiplex the ADC - it only reads once every 15 minutes so plenty of time to play with .

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K.C. Lee wrote 05/27/2019 at 13:10 point

Use a thermal couple next time.  They'll handle very high temperature as it is just a special wire with 2 different metals.  They and the needed sensor board are available from the same place for around $5.

It could be a whole lot of possible causes - bad chip, bad wires.  Wire insulation especially ones from China are bad and as the plasticizer leeches which is accelerated by high temperatures, they can become brittle.  Also Chinese wires cheap out on the copper.

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Thomas wrote 05/27/2019 at 20:27 point

KTY10 sensors worked for me (more than 15 years, max. temperature well above 100*C).

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