Post by thread:Relative Humidity Sensor

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_OUTjerryTakeThisOuTcanlinks.com >

<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. .....jamesnewtonKILLspam@spam@geocities.com 1-619-652-0593 phone

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

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: ralKILLspamlcfltd.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" ================================================================

>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

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}>Thanks in advance for any info > >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. > >Thanks > >Jerry Iacobucci ------------------------------------------------------------------------ Tom Handley New Age Communications Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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: .....ralKILLspam.....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" ================================================================