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A question about HS1101 humidity sensor

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freedomtruth

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Hi friends

I'm going to use humirel HS1101 capacitive humidity sensor in my incubator project and to attain highest accuracy it can give.
I decided to use 555 circuitry recommended in the datasheet. The problem is that this circuit is sensitive to 555's manufacturer.
I couldn’t find one of those 555s listed in datasheet but I bought a 7555 from NXP.
Now my question is what does " internal temperature compensation" mean and what are values for R1 and R2 for my 555?
(Here is a part of the datasheet about 555 circuitry)


thanks in advance
 

freedomtruth

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Apparently as I guessed calculating those resistor values needs complex calculations.
Eventually I decided to calibrate it myself regardless of values given in the datasheet.
As you know HS1101 is a capacitor that changes in value from 160-200pF for air relative humidity of 0-100%. (good linearly)
I replaced the sensor with 160pF and 200pF capacitors to see what are output frequencies for these capacitor values but output freq. for two capacitors of same value varies about 200Hz!! ( i.e. tolerance effect too high)
Is there another way to calibrate it myself?
Any helps would be appreciated. (Sorry for my poor English)
 

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