ds18b20 lost when warm

Other Hardware Sensors
1

Hello,

I just bought a set of DS18B20 waterproof sensors that I tried to interface with my Arduino pro mini.
At the beginning it all started out good: I installed the latest OneWire library, connected the sensor with the 4.7k resistor and got correct readings.

However, I want to use the sensor to measure nearly boiling water temperatures, so I placed the sensor in my kettle. If the temperatures become too high, the device is no longer found. I tried changing the Arduino pro mini for an Uno, and used different sensors. As the sensor gives values at 'low' values, I assume that the wiring is ok. Some of the output from the example script in the OneWire library (DS18x20_Temperature) is listed below. I only use one sensor for the testing, and tried different pins.

Does anyone know how I can remedy this?

19:51:50.483 -> ROM = 28 85 2B 79 A2 0 3 F7
19:51:50.516 -> Chip = DS18B20
19:51:51.503 -> Data = 1 E9 4 55 5 7F A5 81 66 5B CRC=5B
19:51:51.537 -> Temperature = 78.56 Celsius, 173.41 Fahrenheit
19:51:51.608 -> No more addresses.
...
19:51:52.970 ->
19:51:53.142 -> ROM = 28 85 2B 79 A2 0 3 F7
19:51:53.176 -> Chip = DS18B20
19:51:54.167 -> Data = 1 0 0 0 0 0 0 0 0 0 CRC=0
19:51:54.201 -> Temperature = 0.00 Celsius, 32.00 Fahrenheit
19:51:54.234 -> No more addresses.
19:51:54.270 ->
19:51:54.442 -> No more addresses.
19:51:54.476 ->
19:51:54.683 -> No more addresses.
19:51:54.716 ->
19:51:54.952 -> ROM = 28 85 2B 79 A2 0 3 F7
19:51:54.986 -> Chip = DS18B20
19:51:55.978 -> Data = 1 0 0 0 0 0 0 0 0 0 CRC=0
19:51:56.011 -> Temperature = 0.00 Celsius, 32.00 Fahrenheit
19:51:56.077 -> No more addresses.
19:51:56.077 ->
19:51:56.250 -> No more addresses.
...
19:51:57.267 -> No more addresses.
19:51:57.300 ->
19:51:57.514 -> ROM = 10 0 80 0 2 44 4 80CRC is not valid!
19:51:57.584 -> ROM = 10 20 80 0 2 44 4 40CRC is not valid!
19:51:57.617 -> ROM = 10 20 80 0 2 44 4 C0CRC is not valid!

2

bjdekruif:
If the temperatures become too high, the device is no longer found.

Similar problem reported in this thread.
Most likely a fake DS18B20 sensor.
Leo..

3

Proper waterproofing is difficult to do, able to withstand boiling water and changing temperatures, as
special insulating materials like silicone/teflon are needed that don't significantly absorb moisture at high temperature or steam-exposure. I think this could be part of the issue. I found a paper that shows
PVC insulation cannot handle steam at all. https://www.researchgate.net/publication/4341524_Steam-Resistivity_of_Wire_Insulating_Materials

4

Your sensor probably succumbed to water, not heat, I used a small, long necked flower vase, put the sensor in the vase (DRY), submerged the vase in the water WHILE it was heating and got a reading of 99.25. Not sure of the boiling point at my altitude (173 meters). Don't put cold glass in boiling water!
KRACK!

5

I’ve had similar problems ; those sensors aren’t water proof, moisture gets in at the cable connection . If you need to submerge it you need a thermowell ( google) which you can make out of length of copper tube .

6

Hello all,

Thanks for all the replies!

In the mean time, I ordered two sensors from Adafruit, and they work like a charm.

So, for now, I work under the (strong) assumption that I was sold fakes.
If they had problems with the water, I expect they had to last for some time before they broke down.
As a test to see if it is predominantly the heat, I slowly heated it with my soldering iron, and I have the exact same problem.

These were the sensors I had the problems with:

and

I got what I paid for...

Bas