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Problem with ds18b20 values

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Sharagim

New Member
Hi,
In my circuit I am using DS18b20 which is returning values incorrectly.
for example my reference thermometer which is calibrated is showing 26.1 and I am getting 26.8 from DS18b20, when the thermometer is showing 9 I am getting 12.
As you see this in not liner error , Is there any idea what is this problem.?

BR,
 
I read it and unfortunately couldn't find related answer there.
As I mention I am getting result but the result has 2-3 degree different from real temperature, and I should mention here which I am using ds18b20 on pcb.
 
I read it and unfortunately couldn't find related answer there.
As I mention I am getting result but the result has 2-3 degree different from real temperature, and I should mention here which I am using ds18b20 on pcb.

Is there anything on the PCB dissipating any power? PIC? resistors? regulator?
What is the total power input to the PCB (Supply voltage times Supply current)?
 
Thanks for your reply.
I am using a 7.5v(1000 mA) power supply which going to a 5v regulator and then to a 3.3 regulator. My MCU is xmega64a3.
I tried to drive the sensor with both voltage and the result is the same. Then I tried another power supply just for the sensor and I am getting the same result. I used different date codes sensors but no diff.
 
So are you trying to measure the temperature of the pcb or the ambient? With all the stuff on the PCB, I am surprised that it is only three degrees hotter than the ambient temperature...
 
there is metal box which all components are in it and just the sensor is out .
I added about 2cm to The sensor and it is about 5cm out of the box. You think this is not enough?
 
Last edited:
Yes, I think it is not enough. Get an IR thermometer, and aim it at the box...
 
How can 5m outside the box not be enough? Or did I miss something?

Mike.
 
Those damn metric units. I thought he said 5cm...
 
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