I want to know something about Sensirion SHT11 temperature/humidity sensor

sam_sam_sam

HI EVERYONE

I just started playing with this sensor and i have to ask something

·This says·temperature compensated humidity·
·"rhTrue... ", DEC (rhTrue / 10), ".", DEC1 rhTrue, "% "
What dose this mean

·This says·linearize humidity
·"rhLin.... ", DEC (rhLin / 10), ".", DEC1 rhLin, "% ", CR,
·What dose this mean that linear

Is this·to mean a· linear scale in this case
I·just want to make sure that i am understanding this right
·


I do have the demo working ok

This is the demo that i am using

File...... SHT11_Demo.BS2
Purpose... Interface to·Sensirion SHT11 temperature/humidity sensor
Author.... Parallax
Updated... 19 JUL 2003

THANKS to anyone who can help me understand what is the··differcent beteew the two

SAM

Post Edited (sam_sam_sam) : 10/1/2005 4:50:44 PM GMT

Tracy Allen

Hi Sam,

Take a look at the data sheet for the SHT11, from this URL:
www.parallax.com/dl/docs/prod/datast/shtx.pdf

The first thing the program does is grab the raw temperature reading from the sensor, and uses the equation from the data sheet to convert that into degrees Celsius. Actually units of 0.1 degrees Celsius.

The the program reads the raw humidity value from the sensor, but as described in the data sheet there are two steps that need to be done to convert the raw reading into %RH. The reading is slightly nonlinear, and it takes an equation like y = a +bx + cx^2 to convert the raw reading into humidity. That is rhLin. Next, there is an equation in the data sheet that also comes into the program to adjust the RH reading for temperature, and that is rhTrue.

The demo program displays the raw reading, the linearized reading and the temperature compensated reading, just to demo what is going on. But in most programs you would only be concerned with the final value, RHtrue.

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Tracy Allen
www.emesystems.com

sam_sam_sam

HI Tracy

THANKS for explaning that to me
I was not sure if i was understanding the data sheet the right the way or not

THANKS agian for your help

SAM··