Comments on: Soil Moisture Sensor Update http://happyfarming.com/2009/04/16/soil-moisture-sensor-update/ How to Grow Your Own Food Wed, 08 Feb 2012 18:12:30 +0000 hourly 1 http://wordpress.org/?v=3.1.3 By: Thomas W. http://happyfarming.com/2009/04/16/soil-moisture-sensor-update/#comment-56326 Thomas W. Tue, 30 Nov 2010 13:01:31 +0000 http://happyfarming.com/?p=517#comment-56326 @Simon: Thank you for the information - very useful. Good luck with your circuit ;-) @Simon: Thank you for the information – very useful. Good luck with your circuit ;-)

]]> By: Simon http://happyfarming.com/2009/04/16/soil-moisture-sensor-update/#comment-53302 Simon Tue, 23 Nov 2010 00:00:07 +0000 http://happyfarming.com/?p=517#comment-53302 Hey Thomas, I have also been working on a similar circuit (based on that from the emesystems link above). The reason for the variations with temperature is that the resistance of the sensor changes with temperature. The variance is 1% per degree F or 1.8% per degree C. I have found that making this correction that I am getting far more accurate results. It is very important though that the temperature reading is taken right next to the watermark sensor. Hey Thomas,

I have also been working on a similar circuit (based on that from the emesystems link above).

The reason for the variations with temperature is that the resistance of the sensor changes with temperature. The variance is 1% per degree F or 1.8% per degree C. I have found that making this correction that I am getting far more accurate results. It is very important though that the temperature reading is taken right next to the watermark sensor.

]]> By: Thomas W. http://happyfarming.com/2009/04/16/soil-moisture-sensor-update/#comment-12277 Thomas W. Wed, 19 May 2010 08:25:25 +0000 http://happyfarming.com/?p=517#comment-12277 @Michael and Marc: I found this on Wikipedia: "Gypsum is moderately water-soluble (~2.0 – 2.5 g/L at 25 °C) and, in contrast to most other salts, it exhibits a retrograde solubility, becoming less soluble at higher temperatures." AFAIK, the sensor contains a gypsum block. This is strange, because the data shows that when the temperature goes up, the moisture level goes up too. @Michael and Marc:
I found this on Wikipedia:
“Gypsum is moderately water-soluble (~2.0 – 2.5 g/L at 25 °C) and, in contrast to most other salts, it exhibits a retrograde solubility, becoming less soluble at higher temperatures.”
AFAIK, the sensor contains a gypsum block.
This is strange, because the data shows that when the temperature goes up, the moisture level goes up too.

]]> By: Marc MERLIN http://happyfarming.com/2009/04/16/soil-moisture-sensor-update/#comment-11649 Marc MERLIN Mon, 10 May 2010 16:22:35 +0000 http://happyfarming.com/?p=517#comment-11649 Yes, the humidity sensor is super temperature dependent. See http://www.mail-archive.com/owfs-developers@lists.sourceforge.net/msg06064.html Marc Yes, the humidity sensor is super temperature dependent.

See
http://www.mail-archive.com/owfs-developers@lists.sourceforge.net/msg06064.html

Marc

]]> By: Michael http://happyfarming.com/2009/04/16/soil-moisture-sensor-update/#comment-1325 Michael Thu, 07 May 2009 13:03:42 +0000 http://happyfarming.com/?p=517#comment-1325 Inspired by your site I got the same devices. If you find anything further about the relation of soil-temperature and current readings I'd be very interesed.. I found something very interesting here: http://www.emesystems.com/pdfs/SMX.pdf I guess measuring the soil temperature (also while calibrating) and using it for compensation should be possible.. Keep up the good work! Michael Inspired by your site I got the same devices.
If you find anything further about the relation of soil-temperature and current readings I’d be very interesed..

I found something very interesting here:
http://www.emesystems.com/pdfs/SMX.pdf

I guess measuring the soil temperature (also while calibrating) and using it for compensation should be possible..

Keep up the good work!
Michael

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