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Highlighting agricultural developments, problems, research, & issues for central coast CA
Comments:
by Mark Vawter
on September 29, 2019 at 11:48 AM
Very well written instructions for the tensiometer. I was wondering if you had any directions on how to make a connection to a data logger With a 4-20 mA current input? Are there some off the shelf parts that you recommend?
by Michael D Cahn
on September 30, 2019 at 10:37 AM
"Very well written instructions for the tensiometer. I was wondering if you had any directions on how to make a connection to a data logger With a 4-20 mA current input? Are there some off the shelf parts that you recommend? " Mark Vawter  
 
Thanks for your comment Mark,  
 
I use a voltage output pressure transducer (RSU-V)sold by irrometer Inc. to interface the tensiometer with a datalogger. I have been having very good luck with these transducers interms of stability over time and accuracy.  
 
Michael Cahn
by John Clemens
on September 30, 2019 at 5:03 PM
What is unique about the expensive epoxy/hardener you recommend? Since I'm not going to build several hundred tensiometers, I'd like to find a less costly alternate epoxy/hardener combination. Is bonding to the pvc pipe the problem?
Reply by Michael D Cahn
on February 4, 2021 at 11:11 AM
Hi John,  
 
The epoxy/hardener was recommended by soil moisture corp. because it bonds PVC to ceramic materials. We did not try other epoxy products. You might experiment with a similar type of epoxy.
by Michael D Cahn
on September 30, 2019 at 5:20 PM
John,  
I understand your concern with buying the expensive epoxy and hardener. It works well and can be use for gluing many tensiometers but has a limited working life time (1 year).  
 
You can try other epoxy products that are suitable for plastic and ceramic. I suggest to experiment with whatever brand that you choose on one tensiometer first. I have used these expoxies in the past but soil moisture corp. cautioned us against the off-the-shelf epoxy products. One problem that we had was that the epoxy did not harden sufficiently and bond well to the pvc.
by renzo manchinelli
on March 6, 2020 at 5:56 PM
Hi i'm from argentina, is there a way to contact You? Some mail or number? Thank you
by Michael D Cahn
on February 4, 2021 at 11:11 AM
Renzo,  
 
If you have specific questions you can contact me at mdcahn@ucanr.edu
by Stephen Hughes
on April 5, 2021 at 5:51 AM
Very helpful, thanks!
by Andre Kleynhans
on April 8, 2021 at 5:56 AM
Hi, I'm from South Africa  
 
What values on the meter would you say is dry and wet?
by Michael D Cahn
on April 12, 2021 at 7:32 PM
Hi Andre,  
 
For vegetables and berries, readings less than 20 to 25 kPa are considered moist. Dry conditions would be greater than 60 kPa (cbars). Tensiometers typically have readings less than 5 or 10 kPa after irrigating, corresponding to very moist conditions.
 
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