Humboldt H-4200F Soil Penetrometer - Manual (Page 2)

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General
The Pocket Penetrometer is designed as a lightweight instrument for use by
field personnel to check visual classification of soils. It can be used to verify
whether excavation side walls require shoring, based on OSHA cohesive
soils classifications.
It indicates consistency, shear strength, and approximate unconfined shear
strength. Direct-reading scale—in tons/sq ft, or kg/sq cm—corresponds to
equivalent unconfined compressive strength. The readings obtained from
the Penetrometer do not replace laboratory test results due to the fact
that a small area of penetration test could give misleading results. The
instrument should not be used for obtaining foundation design data.
Instruction
The scale indicator must be fully inserted into the Penetrometer body until
the "0.0" mark only is showing. The stainless steel piston (opposite end of
the scale indicator) has a tip area of 0.05 square inch (0.32 sq. cm). In use,
it is pressed into the soil until the engraved line, 1/4" (6.35 mm) from the
tip, reaches the soil level. A reading can now be taken from the scale
indicator. The scale is calibrated in tons per square foot or kilograms per
square centimeter unconfined compressive strength.
Maximum reading of the Penetrometer is 4.5 tons per square foot or 4.5
kilograms per square centimeter. Pocket Penetrometers are not individually
calibrated and therefore, no calibration certificates are supplied. An error of
up to 1/2 division on the scale, equivalent to 0 to 0.124 TSF, is possible with
the instrument.
Adapter Foot
The H-4200F Adapter foot is recommended when testing extremely
low strength cohesive soils. 1" (25mm) dia. foot, compared to the 1/4"
(6.35mm) penetrometer piston, increases the effective area measured by
16 times. Divide by 16 to obtain correct unconfined compressive strength
when the reading in tons per square foot or kilograms per square
centimeter is on the low-load side.