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a mysterious sensor

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  a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-04-30 18:19 +0000
    Re: a mysterious sensor tabbypurr@gmail.com - 2017-04-30 12:08 -0700
    Re: a mysterious sensor Hul Tytus <ht@panix.com> - 2017-04-30 21:49 +0000
    a mysterious sensor pcdhobbs@gmail.com - 2017-04-30 15:04 -0700
      Re: a mysterious sensor Cursitor Doom <curd@notformail.com> - 2017-04-30 23:02 +0000
        Re: a mysterious sensor BM2335 <BM265@DMM.com.au> - 2017-05-01 11:19 +0800
      Re: a mysterious sensor Don Kuenz <g@crcomp.net> - 2017-05-01 03:06 +0000
        Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-01 08:17 +0000
      Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-01 08:16 +0000
    a mysterious sensor Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-04-30 15:46 -0700
      Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-01 08:20 +0000
    Re: a mysterious sensor Jon Elson <elson@pico-systems.com> - 2017-04-30 21:27 -0500
      Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-01 08:21 +0000
        Re: a mysterious sensor Jon Elson <jmelson@wustl.edu> - 2017-05-01 14:13 -0500
          Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-01 19:42 +0000
    Re: a mysterious sensor Frank Miles <fpm@u.washington.edu> - 2017-05-01 02:53 +0000
      Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-01 08:24 +0000
    Re: a mysterious sensor George Herold <gherold@teachspin.com> - 2017-05-01 05:11 -0700
      Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-01 14:21 +0000
    Re: a mysterious sensor "nuny@bid.nes" <alien8752@gmail.com> - 2017-05-01 13:17 -0700
      Re: a mysterious sensor Jan Panteltje <pNaOnStPeAlMtje@yahoo.com> - 2017-05-02 07:46 +0000

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#458347

On a sunny day (Mon, 1 May 2017 13:17:00 -0700 (PDT)) it happened
"nuny@bid.nes" <alien8752@gmail.com> wrote in
<fc7d4f35-a006-40b7-ab85-843d1ae93a3d@googlegroups.com>:

>On Sunday, April 30, 2017 at 11:19:10 AM UTC-7, Jan Panteltje wrote:
>> Hi,
>> been doing some sensor stuff.
>> I connect those to a PIC micro and an POE ethernet module, and send UDP data
>> that way.
>> 
>> Today was the turn for the relative humidity and temperature sensor DHP11.
>> 
>> It is supposed to be within a few percent accuracy for RH.
>> 
>> However with 60 % RH it displays 20 %....
>> I have 2 and both do the same, software is good and checksum of communication
>> is good.
>> 
>> So started googling, seems MANY people have the same problem,
>> nobody solved it, some people just wrote some correction math...
>> That is what I am doing now too (and ordered an other sensor type).
>> 
>> But, playing with it, trying to find out what I did wrong or what was wrong
>> with those sensors:
>> 
>> I noticed that if I put my finger on it the reading went way up from 20 % to
>> over 60 %.
>> 
>> Heat? no, also if I put my finger 5 mm away next to it...
>> Tried a light bulb (Edison type), hot, no effect on RH.
>> Tried a hot piece of metal: no effect on RH.
>> Tried a dark screen, tried a high brightness CREE flashlight: no effect.
>> Tried radiation sources (uranium marbles, thorium rods): no effect.
>> 
>> Tried a wet piece of cloth next to it, way up it goes.
>> But but, my fingers are DRY.
>> 
>> So dry I need to wet those to open a sandwich bag...
>> 
>> So WTF is going on ?
>
>  Seems electrostatic to me.

I did check for that (electric signal coupling) by grounding myself.

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