James Rebarscope R-C-400 Operator's Manual page 27

Step 5: Place the sensor on top of the surface where the rebar
diameter is to be measured. If the reading on the first line is larger
than 3000, use the 1 5/8 inches spacer block between the concrete
surface and the sensor. If reading is still above 3000 it may be
necessary to add an additional non-metallic block underneath the 1
5/8 block. (Note: The optimal cover range for sizing is between 1.7"
and 4.2". Also, the most accurate sizing of rebar occurs when the
first measurement is about 1200.)
Step 6: Once the center has been determined, press Enter for a
few seconds to store the result.
Step 7: The Rebarscope® will now read ADD BLOCK PRESS ENT
on the top line.
Figure 19: Add Block is displayed
At this point the locating template needs to be placed alongside of
the sensor probe; so the exact location of the first reading can be
kept. Note: Taking the second reading at the exact location as the
first is critical for precision. While holding the locating template,
remove the sensor probe and place the 3/8 inch spacer block along
the locating template.
Step 8: Now place the sensing probe over the 3/8 inch spacer block
and press Enter. The Rebarscope® will now display the estimated
diameter of the measured rebar. The Rebarscope® can accurately
determine bar size up to a cover of 4.5" (115mm) in Deep mode.
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