View Full Version : Relitive Humidity measurement

02-24-2010, 03:09 AM
Hello, I'n looking for an effective·way to measure the relative humidity in a given space over a period of time, 24hr. and sending·the info·to a data logger for evaluation and charting at a later date. I have done it with temperature and it works well but now I need to account for humidity. I am not aware of a good relative huminidty sensor. Please advise!

Tracy Allen
02-24-2010, 04:28 AM
Parallax sensor (http://www.parallax.com/tabid/174/List/0/CategoryID/49/Level/a/Default.aspx?SortField=ProductName,ProductName) item 28018 is an SHT11 temperature/humidity sensor with digital interface, quite accurate. Item 27920 is a cheaper sensor that would need more interface and calibration.

Tracy Allen
www.emesystems.com (http://www.emesystems.com)

WBA Consulting
02-24-2010, 06:45 AM
The SHT11 sensor that Tracy mentions is ideal for logging accurate temp and humidity readings from a single device. It is very stable and it's accuracy/ease of use combination isn't currently matched by anything else out there now. I have used the SHT11 sensor with the stamp and logged temp and humidity data.

Not sure which data storage method you are using, but here is a link to my BS2P40 Plungelogger (http://forums.parallax.com/showthread.php?p=792332) that used a VMusic2 module. The VMusic2 module uses the same code format as Parallax's 27937 Memory Stick Datalogger. Here's a link to BS2 code that reads two SHT11 sensors (http://forums.parallax.com/attachment.php?attachmentid=56212) and displays it on an LCD.

I have since moved to the Propeller and have the same project, but now log directly to SD cards. For this year's plunge, I am also modifying a pocket sized display unit (http://www.eders.com/products/moultrie-digital-picture-viewer.html) that will read the data off the SD card and graph results on a 2" display, so I can get immediate, detailed results without a computer.

Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module (http://www.aestheticacoustics.com/sht11_01.htm)
Special Olympics Polar Bear Plunge, Mar 20, 2010 (http://www.kintera.org/faf/donorReg/donorPledge.asp?ievent=322002&lis=1&kntae322002=BDAEE98623FB443591C072E356710D6B&supId=265642883)
Propeller-Based Reverse Geo-Cache Birthday Present Project (http://forums.parallax.com/showthread.php?p=869153)

Post Edited (WBA Consulting) : 2/23/2010 11:55:50 PM GMT