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PICList Thread
'Relative Humidity Sensor'
1999\09\22@180240 by Jerry Iacobucci

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1999\09\22@182327 by Dan Larson

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On Wed, 22 Sep 1999 17:57:51 -0400, Jerry Iacobucci wrote:

>Thanks in advance for any info
>
>Has anyone come across a company that produces a device (sensor) that will meas
ure relative humidity, or know of a device.  I need to interface to a pic.

Honeywell produces a range of humidity sensors.

Phillips has some as well.

I don't know the part numbers off hand, but I did a search
for humidity sensors a while back.  All of my notes and
data sheets are at home :-(

ANyway, have a look at

http://www.honeywell.com/sensing/prodinfo/humiditymoisture/

I think you can get links to disttributors from their
web site some how.

Dan


>
>
>Thanks
>
>Jerry Iacobucci
>
>spam_OUTjerryTakeThisOuTspamcanlinks.com
>

1999\09\22@182330 by eplus1

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<BLOCKQUOTE AUTHOR="Jerry Iacobucci">Has anyone come across a company that
produces a device (sensor) that will measure relative humidity, or know of a
device.  I need to interface to a pic.</BLOCKQUOTE>

Humidity
see also:
Honeywell: www.honeywell.com/sensing/prodinfo/humiditymoisture
http://kitsrus.com
http://www.columbia-center.org/fascinating/comp/comp.html its $14.9 and puts
out a capacitance related to the humidity.

Moisture
see also:
Quantum Research Group. QProx One chip proximity sensors.
http://www.xs4all.nl/~sbolt/e-index.html
www.xs4all.nl/~sbolt/e-groeneVinger.html
www.columbia-center.org/fascinating/obs/instrmnt.html
Irrometer Co., Box 2424, Riverside, CA 92516 Phone 909-689-1701 osmosis
principle measuring capacitance
http://www.michell.co.uk


James Newton, webmaster http://get.to/techref
The stupid javascript has been removed from the submit button...
Sorry if you couldn't get access before, please try again.
.....jamesnewtonKILLspamspam@spam@geocities.com
1-619-652-0593 phone

1999\09\22@202528 by Darren Logan

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Just thought I'd let you know :-

I am a development engineer at Michell instruments (http://www.michell.co.uk).

Most of the newer products on this site are my own design.
(Takes a bow)

It was nice to see our web site as part of a discussion on this list.

You may think this is salesman woffle, but Michell Instruments IS the world
leader in moisture measurement and generation. DONT go anywhere else for your
moisture applications.

Look out for a product called TRANSMET (stands for TRANSmitter METeorlogical).
This is our hottest seller. 3-wire dewpoint transmitter capable of humidity
measurement down to -100 degC dewpoint (1 part of water per billion parts of
air) and up to +20 degC dewpoint. 1 degC dewpoint accuracy !!. 4-20mA /
0-20mA output over the range.
Also RS232 output and RS485 networkable.
Guess who designed this ? (hee hee)

(Dont forget to mention my name to our sales guys and tell them where you saw
the advert !!)

Regards,
Darren

1999\09\22@223143 by Robert A. LaBudde

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At 05:57 PM 9/22/99 -0400, Jerry wrote:
>
> Has anyone come across a company that produces a device (sensor) that will
> measure relative humidity, or know of a device.  I need to interface to a
> pic.


There are several companies in the US that produce cheap capacitative relative
humidity sensors.

First you should decide what your requirements are:

1. Do you require operation up to 100% RH (i.e., condensing). Some sensors will
operate submerged in water; others will be permanently decalibrated by
condensation.

2. What accuracy do you need? Typical inexpensive sensors can be calibrated to
perhaps 1% at a point or 2% over a range. High accuracy requires a
chilled-mirror dewpoint measurement approach, which is much more expensive.

3. Do you require pre-calibration, or will you do it yourself? Uncalibrated
polymer sensors cost only about $1 each in small quantities. Calibrated sensors
cost several times this, but are good to +/- 2% RH over the operating range out
of the box.

4. Package size.

5. Response time.

6. Durability.

I have a few such sensors (both calibrated and uncalibrated) I got as
development kits a couple of years back. The measurement circuit is basically a
capacitance meter, so you can connect a 555 and output a pulse width to a pic
or a frequency you can count.

Unfortunately, I can't find any mention of the maker of the pre-calibrated
sensors. The maker of the cheap, uncalibrated sensors is

       Panametrics
       Waltham, MA 02154
       (617) 899-2719 (check area code, may have changed)
       http://www.panametrics.com/

A polymer capacitative sensor usually varies between 100 pF and 200 pF for
0-100% RH.

"Sensors" magazine is a good place to check for ads:

       http://www.sensorsmag.com/


================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: ralspamKILLspamlcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causae scire"
================================================================

1999\09\23@123610 by Reginald Neale

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>At 05:57 PM 9/22/99 -0400, Jerry wrote:
>>
>> Has anyone come across a company that produces a device (sensor) that will
>> measure relative humidity, or know of a device.  I need to interface to a
>> pic.
>
>
>There are several companies in the US that produce cheap capacitative relative
>humidity sensors.
>

If you only need 5% accuracy, TDK makes the CHS series sensors.
5VDC in, 10mV/%RH out. These are high impedance (200K) devices,
so you need some interface circuitry to make it work.

Reg Neale

1999\09\23@125700 by Tom Handley

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  Jerry, I designed a PIC-based weather station a few years ago. There are
several options to measure humidity. You have to make a decision based on
environment, accuracy, cost, and ease of use. There is no simple answer
without knowing more about your project.

  Low-cost humidity sensors behave like capacitors that vary with
humidity to change the frequency of an external oscillator. Typical relative
humidity ranges from 10 - 90%. Philips makes (or use to) a low-cost sensor
(P/N 2322 691 90001). General Eastern also have low-cost sensors in their
G-CAP line. Their sensors cover 1 - 100% RH.

  For my project, I needed better accuracy and I wanted to reduce the
complexity of the support circuitry. I ended up using HyCal sensors which
provide an output within 0 - 5V and require minimal support. The outdoor
sensor is an IH-3602L which comes in a T0-39 can with a slotted cap and for
the indoor sensor, I used the IH-3605 hybrid element. Both sensors operate
from 1 - 100% and provide an output from around 0.8V - 3.9V with a 5V
supply. They should be buffered and require a simple low-pass filter and, as
with most sensors of this type, need to be shielded from sources of bright
light. You do need to factor in temperature compensation so you need to
measure ambient temperature near the sensor. You normally combine both in a
package for your outdoor sensors.

  There are more sophisticated sensors that provide a voltage, current, or
pulse output and include the temperature sensor giving humidity and/or dew
point. For more info contact:

     HyCal: www.honeywell.com/sensing/prodinfo/humiditymoisture
     General Eastern: http://www.geinet.com/
     Philips        : (817) 325-7871 (Note, may be discontinued...)
     Omega:         : http://www.omega.com

  - Tom

At 05:57 PM 9/22/99 -0400, Jerry Iacobucci wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

1999\09\23@205711 by brooke

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Hello Jerry:

Have a look at my sensors web page at:
http://www.pacific.net/~brooke/Sensors.html#Humidity

73,

Brooke

1999\09\23@234146 by Robert A. LaBudde

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At 05:55 PM 9/23/99 -0700, Brooke wrote:
>Hello Jerry:
>
>Have a look at my sensors web page at:
>http://www.pacific.net/~brooke/Sensors.html#Humidity

Check out Brooke's sight: It's awesome!

PS. The calibrated RH sensor I mentioned before is made by General Eastern:

       http://www.geinet.com/RH/rhgcap.htm


================================================================
Robert A. LaBudde, PhD, PAS, Dpl. ACAFS  e-mail: .....ralKILLspamspam.....lcfltd.com
Least Cost Formulations, Ltd.                   URL: http://lcfltd.com/
824 Timberlake Drive                            Tel: 757-467-0954
Virginia Beach, VA 23464-3239                   Fax: 757-467-2947

"Vere scire est per causae scire"
================================================================

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