Dear SoWaCS members - TWO Brief administrative notes: 1/ Please put the word "sowacs" somewhere in the Subject or in the first few lines of any messages. This makes it easy for those receiving a lot of email to know that the message is ^really^ important! 2/ Those having private email discussion amongst yourselves, please take the time to post a summary of your findings (or the ongoing topic if not yet complete) so that the rest gain the benefit of your collective wisdom. After all, if you made contact with others through this list, then please have the courtesy to repay the list by sending your summaries in. Thanks Bruce Metelerkamp (SoWaCS Host) -------------- There are four matters of business: 1/ A transcript (from Japanese) of a message on the Japanese Hydrology USENET by Masato Fukumoto of Hokkaido National Agricultural Experiment Station on TDR systems.... 2/ Development of sensors - should we be aiming at cheap or accurate sensors? 3/Putting my money where my mouth is : The discussion I currently am in concerns whether one can simply reduce the length of TDR wave-guides and simply correct by recalibration. This appears to be limited by the capacity of the particular sensor's electronics to resolve the wave's reflection time. And some sensors have internal electronics configured for distances and so cannot be changed. 4/ Another point I am trying to get discussion on is how to calibrate TDR (and related) sensors. A simple two-point (oven-dry and saturated) is surely not appropriate if the main use for the sensor will always be inbetween these. Obtaining uniform water contents at points in between will surely involve either a lot of mixing and repacking of sequntially wetted soil, or long time periods to allow redistribution of soil water added from the top or bottom? ============================= 1/ A transcript (from Japanese) of a message on the Japanese Hydrology USENET by Masato Fukumoto of Hokkaido National Agricultural Experiment Station on TDR systems.... There are two standard TDR system manufactures. One is TDR Soil Moisture Measurement System of CAMPBELL SCIENTIFIC INC.(CANADA) that combines Tektronix 1502B Cable Tester with CAMPBELL SCIENTIFIC 21X datalogger. Another one is Trase Systems 6050X1 of SOILMOISTURE EQUIPMENT CORP. (U.S.A) that include Cable Tester and datalogger as one pack. These manufactures are expensive using very precise equipment in order to measure the TDR wave form. I am using Trase Systems 6050X1. One side, there are cheap or strange manufactures. Those are TRIME SYSTEM of IMKO(GERMANY), MOISTURE POINT of ?(GEIRUGABERU, by spelling in Roman letters) CORP. (CANADA) and others. After I have presented above-mentioned contents on mailing, I sent that reply message (in Japanese). The contents of that message are (1) what method to measure the pulse travel time is used by TRIME SYSTEM (that I guessed by reading the technical report of IMKO) , (2) I don't know what method to measure the pulse travel time is used by MOISTURE POINT, (3) why volcanic ash soils having well-developed aggregate structures are different from the common relationships derived by Topp et al.(1980). I'm sorry that I can't explain (1) and (3) in detail in English. I guessed that MOISTURE POINT may be base on the method by Hook et al. (1992, SOIL SCI. SOC. AM. J., Vol.56, 1384-1391). But I can't understand the method. Judging by user' talk, I encourage TRIME SYSTEM (this is cheap), but don't encourage MOISTURE POINT. Please pay attention this individual comment. By the way, let me introduce my study. I study about soil physics, meteorogy and microwave remote sensing by one's own. I reported the Japanese papers (1) applicability of suirrigation in clayey paddy fields converted to upland fiels, (2) the effect of surface soil moisture on heat balance at a bare soil surface and (3) the effect of soil texture on the dielectric property and the microwave backscatter property. In (1) I measured the soil water suction by 100 tensiometers. In (2) I measured the soil moisture within the top 2cm layer by sampling the soil every day in 90 days. (3) is reported about experiment result relative to the technique of using microwave radar to remotely observe surface soil moisture. Now I'm studing (1) heat balance at a spase canopy (2) microwave backscatter property at the freezing soil. Regards ------------------------------------------- Masato Fukumoto Hokkaido National Agricultural Experiment Station Lab. Agricultural Engineering ----------------------------------------------- 2/ I am again sending out Marty's appeal for feedback on whether there is a greater need for cheap or accurate sensors:- In my opinion, the accurate sensors are available, and are being used by those who require the accuracy. What is not available are some kind of dime-a-dozen sensor for use where a large number of samples are required. These could be used in parralel with a few more accurate sensors to "correct" and so kill both the birds of accuracy and increased sampling points with one budget (so to speak). MARTY's original message. (Marty perhaps you would post a summary of the responses you recieved?)... From: Marty Grogan (ges) To: SOWACS@aqua.ccwr.ac.za Date: Saturday, May 25, 1996 10:25 pm Subject: Re: Sensor design economics--Your comments, please I am developing a soil moisture sensor using a proprietary technology and have encountered a delima. I can produce very accurate, stable sensors which cost a lot (~US$500) or relatively inexpensive sensors (~US$15.00) which operate very much like switches. If you have any opinions with regard to price/performance/flexability tradeoffs, I will quickly become "all ears." Also, if you are willing to provide "beta site" evaluations, I would like to provide you with such an opportunity. Marty Grogan, Owner Grogan Engineering Services END From: Bruce Metelerkamp (BRUCE) To: SOWACS@aqua.ccwr.ac.za Date: Thursday, June 20, 1996 12:44 pm Subject: Sowacs - attached file name With reference to the attached file I just sent out to sowacs: " Bruce Metelerk 06/20 12:24 Enclosure file: FUKU " Talk about grabbing your attention; - the filename I used was simply the first few letters of the surname of "Masato Fukumoto" whose message I edited and then distributed. This was done totally in innocence, and the file name I thought usually doesn't even appear anywhere. Apologies if anyone thought otherwise. Those wishing to respond to Masato, please do so through me: bruce@icfr.unp.ac.za -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-. Bruce Metelerkamp SOIL WATER RESEARCH OFFICER Institute for Commercial Forestry Research, University of Natal, PO Box 100281 Scottsville, ZA3209 Rep. of South Africa Voice:27 331 62314 E-mail: bruce@icfr.unp.ac.za FAX:27 331 68905 URL http://www.icfrnet.unp.ac.za/~metele /SoWaCS.html /RR.html Host of SoWaCS (Soil Water Content Sensor) Discussion List. SEND info sowacs OR subscribe sowacs TO majordomo@aqua.ccwr.ac.za