TRENCH OFFSETS
If the gauge is to be used for moisture or density measurements in a
trench or within two feet (0.6 m) of a large vertical structure, a
trench offset may be required. If used, the trench offset adjusts all
moisture measurements but only the density measurements from
backscatter through four inches (10 cm).
To perform a trench offset:
Take the daily standard count (outside the trench) and record the
density count (DS) and moisture count (MS) values.
Place the gauge on the reference standard block in the trench the
same distance from the wall as the anticipated readings. Do not
take another standard count.
Set the count time to four minutes.
With the source rod in the SAFE (standard count) position, take
a four-minute count. To start the count, press the
〈START/ENTER〉 key.
Record the trench density count (DC
Trench
) and moisture count
(MC
Trench
.).
Subtract the daily standard count values from the trench count
values:
Dens Cnst = (DC
Trench
) – DS
Mois Cnst = (MC
Trench
) – MS
To enable a trench offset, press 〈SPECIAL〉 to access the Special
functions, then press the down arrow key once to access the Offset
function. Press 〈START/ENTER〉 to display:
Offset: Density
(↑ ↓ or ENTER)
3–6
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