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Luca Mastrorillo Debora Montilii-- Are you making or buying your "Frequency Domain" sensor? What prompted your decision to use 20 MHz frequency? If adjustable, I would suggest making measurements at several frequencies--According to Romain Gagnon, Smart Rain's sensor operates in the 100-325 MHz range. Also according to Romain, below 100 MHz, granularity of soil affects permittivity and therefore, statistical accuracy. We are in the process of buying a Campbell Scientific CS615-L TDR sensor and I am planning to build probes of our own. The Smart Rain sensor seems to be very advanced and I would prefer it. However, as it is an integral part of a bi-directional system, it also requires an Echelon LonWorks board and a power transformer--too expensive for our initial investigation of TDR. 20 MHz is in the 15 meter HF shortwave radio band. 20.000 MHz is used by WWV (US) and other countries around the world to broadcast time, solar and weather information. Be sure your equipment is well shielded and grounded so it does not interfere with radio reception. Please keep us posted on your progress, both via SoWaCS and directly. Dave Barnett UMass CEE Dept > >Date: Wed, 20 Nov 1996 11:52:41 -0500 >From: <montilii@cclix1.polito.it> >Subject: soil water content sensor >To: sowacs@aqua.ccwr.ac.za > >Return-path: <majordom@aqua.ccwr.ac.za> >Received: from aqua.ccwr.ac.za by ECS.UMASS.EDU (PMDF V5.0-7 #6523) > id <01IC2GE6QIR4A9MG33@ECS.UMASS.EDU> for dbarnett@ecs.umass.edu; Wed, > 20 Nov 1996 11:52:16 -0500 >Received: by aqua.ccwr.ac.za (AIX 4.1/UCB 5.64/4.03) id AA27830; Wed, > 20 Nov 1996 09:09:10 +0000 (GMT) >Received: from pol88b.polito.it by aqua.ccwr.ac.za (AIX 4.1/UCB 5.64/4.03) > id AA27892; Wed, 20 Nov 1996 11:07:33 +0200 >Received: from cclix1.polito.it.polito.it (cclix1.polito.it) > by polito.it (PMDF V4.2-15 #3020) id <01IC2CPUX9PS8WWHNN@polito.it>; Wed, > 20 Nov 1996 10:06:08 GMT+1 >Received: from cclinf.polito.it.polito.it by cclix1.polito.it.polito.it > (4.1/SMI-4.1) id AA05938; Wed, 20 Nov 1996 10:05:42 +0100 >Date: Wed, 20 Nov 1996 10:05:42 +0100 >From: montilii@cclix1.polito.it (Linux-montilii (7051)) >Subject: soil water content sensor >Sender: owner-sowacs@aqua.ccwr.ac.za >To: sowacs@aqua.ccwr.ac.za >Message-id: <9611200905.AA05938@cclix1.polito.it.polito.it> >Content-transfer-encoding: 7BIT >Precedence: bulk > > >We are making a study with a soil water content >sensor (Frequency Domain sensor) that works at >20 Mhz. >Is there anyone who knows if there are any problems >in working at that frequency ? >Is it possible to have problems about polarization >of the water molecules in the soil that false the >measurement? If yes, why? > >thank you in advance, > >Luca Mastrorillo >Debora Montilii >Politecnico di Torino - ITALY > >E-mail: montilii@cclix1.polito.it >