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[wxsig] Rain Gauge Calibration

Clay Cottingham Clay at Cottingham.net
Mon Feb 21 05:25:37 UTC 2005

Trying to understand the theory behind the operation of the rain gauge.

I have the original Dallas Semiconductor rain gauge. The instructions that
come with it state to "Adjust the calibration screws so that 16 Oz at the 1
inch per hour rate produces 100 counts." This appears to correspond to 1.00"
indicated on the T238 display.

Where I am confused is this: Taking the measurement of the radius of the
rain gauge and caculating the area exposed and converting to ounces gives me
about 15 ounces per inch of rain:

5.875 inches diameter
2.9375 inches radius

= 27.109 square inches

At 1" of rain, this would be 27.109 cubic inches

Converting cubic inches to ounces;

1.80468751 cubic inches per ounce

= 15.021 ounces.

Why then do you calibrate with 16 ounces?

Want to make sure I get this right before I go mount it on the pole!



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