View Full Version : SHT11 Temperature Offset

01-21-2006, 03:44 AM
Hello All,

I'm working with a SHT11 Sensor Module and a BS2P40 on the P40 Demo Board.· I'm reading a temperature from the SHT11, but it has an offset (high) of about 8-9 degF from the acutal room temperature.· I'm using my wife's digital meat thermometer·http://forums.parallax.com/images/smilies/shocked.gif to verify the actual temperature along with one of those digital clocks that show indoor temperature and they both agree that the SHT11 is high by 8-9 degF.

So my first guess was that the internal heater for the SHT11 is on, so I loaded the advanced SHT11 demo software·and executed the·Heater_Off subroutine in the "Initialize" section.··· This made no difference.

So does anybody have any ideas or seen this before?


Jon Williams
01-21-2006, 04:01 AM
Getting from raw counts to temperature is a bit tricky with the SHT11, but in my experiments I only ever saw it off by a couple degrees.· Dr. Tracy Allen has done a lot of work with this sensor, you might have a look at his page.


Jon Williams
Applications Engineer, Parallax

01-21-2006, 09:53 PM
Just a note that the Sensirion data sheet reflects temp accuracy of +/- 0.4 deg C at 25deg C for this device.

"Single chip sensor module, fully calibrated with digital 2-wire output. 0-100%, -40 to 120°C, fully immersible, accuracy +/- 3%RH, +/- 0.4°C @ 25°C, response time humidity sensor 4s"


01-21-2006, 11:21 PM
that's its accuracy at that temp....I've seen some sensors with a HUGE curve on them....not linear at all!
Check the data sheets and see if they have a temp calibration curve chart....

Even those old mercury thermometers (and alcohol ones) have curves to them.



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01-22-2006, 12:19 AM
Not to belabor the point but, the datasheet reflects· "~" ·+/-1 degC accuracy for the range 0 to 40 deg C (32 to 104 deg F) for this device.