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Re: a mysterious sensor

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On a sunny day (Mon, 01 May 2017 14:13:49 -0500) it happened Jon Elson
<jmelson@wustl.edu> wrote in <guOdnf4xx4zzFZrEnZ2dnUU7-YOdnZ2d@giganews.com>:

>Jan Panteltje wrote:
>
>> On a sunny day (Sun, 30 Apr 2017 21:27:53 -0500) it happened Jon Elson
>> <elson@pico-systems.com> wrote in
>> <H5idnVTVQpa1AJvEnZ2dnUU7-dWdnZ2d@giganews.com>:
>> 
>>>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.
>>>> 
>>>I've been using Phys_Chem Scinetific humidity sensors in my environmantal
>>>monitoring system for 20+ years.  They seem to work quite well, and
>>>although I have not rechecked the calibration, it seems to still be
>>>reasonable. These are capacitive sensors, and need a circuit built out of
>>>an Analog Devices audio chip.
>>>
>>>Jon
>> 
>> Interesting, frequency change based? Or leakage based?
>Oh, boy, this requires deep digging in the old memory banks.  I THINK it 
>uses constant frequency, and measures the capacitance by how much AC is 
>coupled to a resistive load.  I THINK that's how it works.  I built these 
>from an app note almost 30 years ago, and they've just been perking along 
>since. 

OK, datasheet of the new sensors I ordered (google AM2302.pdf many links) says it is capacitive too.
This DHT11 I am having problems with, says it uses a resistive type.
The fact that yours works so well for so long gives me hope the new sensors will be OK.
The DHT11 that gave 20 % RH now gives 48 % RH while it is 60 % RH, fast aging, was outside all night and it rained :-)
Just wrote the PIC asm code for that AM2302, slightly different from the DHT11, so am ready when those arrive.


>I think these sensors are the same type as used in a number of VCRs 
>to shut them down if close to dew conditions.

Ha, Sony Umatic helical scan, I remember in Rome in a sports hall needed to record, and the d*mn thing would not.
used an electric heater blower to get it working just in time :-)
Now that was long ago too.

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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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