Humboldt H-4120HA Corps of Engineers Cone Penetrometer - Manual (Page 3)

3
G. CAUTIONS: Observe the following cautions:
1. Keep the instrument vertical.
2. Do not attempt readings higher than the capacity of the dial since this might
overstress the proving ring .
3. If the dial capacity is exceeded at less than 18 in. (457.2 mm) of penetration,
make another penetration nearby to be assured that the cone is not striking
an isolated rock fragment.
4. Never withdraw the instrument by the ring but always by the rod.
CARE AND ADJUSTMENT OF THE PENETROMETER
A. General Care
The penetrometer needs little care beyond keeping the instrument free from
dirt and rust, keeping all parts tight, and frequently checking and, if necessary,
re-zeroing the instrument. Take particular care to see that no grit is caught
between the extensometer arm of the dial and the lower mounting block
(#10 Figure 1).
B. Dial Gauge
The dial indicator is a sensitive instrument, which should be protected against
water and rough usage. Never immerse it in water. Wipe it dry as soon as
possible after its use in rainy weather. When transported by truck, cushion the
dial by wrapping it in paper or cloth.
C. Mounting- block Adjustments
If either or both mounting blocks (#10) become loosened or moved, adjust
them so that they lie on a diameter of the ring, and then retighten.
D. Cone Replacement
Considerable use of the same cone may result in a rounding of its point. This
will not affect the accuracy of the instrument, but if the base of the cone has
had excessive wear or is deformed by hard usage, the cone should be replaced.