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In response to the Gypsum block temperature response.
First I apologize for appearing anonymous! I thought my name and E-mail
address were automatically attached.
The Cary temperature correction to gyp block readings was given as
Correct Resistance to the temperature at which they were calibrated (22 C)
R22=((T^0.011 -1)*(T-22)+1)*Rmeasured
Cary presented a formula to convert R22 to H22 (kPa) as
H22 (kPa) = 0.0217*R22 + 69.84*Ln(R22)-3.245*SQRT(R22) -310.5
H (bars) = H22(kPa)/100
Using the Cary relationships the following table was generated
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[Contents of which is:]
Bars 22.0 30.0 20.0 10.0
15.0 92006.6 19.9 13.9 10.3
6.0 36812.4 7.7 5.6 4.3
0.6 480.0 0.7 0.6 0.4
Column 1 is tension in bars at 22 C, Column 2 is R22 required to obtain
Col. 1, and the other columns are computed tensions using the R values in
Col. 2 and can be considered to be tensions estimated as Rmeas but not
corrected for temperature.
Obviously these corrections at not as large as I reported in the
"anonymous" note and I offer my apologies for overstating my case. But the
corrections are none the less substantial.
A positive note is that the electronics can be changed around to self
correct for temperature. First make a reference block by conditioning one
gyp block to some tension and seal it in epoxy so that the tension is
fixed. Place the reference block in series with a block in soil. Then use
the voltage drop across the block in soil. I have not tried this but it
looks good on paper!!!
buck sisson, jys@inel.gov
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