Humboldt H-4195 Soil Penetrometer, Pocket Style - Manual (Page 2)

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 red ring on the barrel of the penetrometer is designed to maintain the
test reading on the scale for easy reading.
To operate, slide the ring down against the handle (knurled portion) of the
penetrometer. Grip the handle and push the tip of the penetrometer into
the soil so the groove marked on the tip is even with the level of the soil.
Once this is done, you can read the scale to determine the unconfined
compression strength directly from the scale in tons per square foot (TSF) or
kilograms per square centimeter (kg/cm 2 ).
The reading should be taken from the lower side of the red ring, i.e. the side
closest to the knurled handle.
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.
Notes:
Select test spots with a smooth surface. Hold the pocket penetrometer at
right angles to the surface being tested. To minimize errors, take several
readings near each other, discard those readings that may vary significantly
from the majority and average the readings.
Adapter Foot
The H-4195F Adapter F oot 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.