Product Manual

6
Control: Operational Check and to Verify Calibration
A 12x12 inch foam calibration pad is provided for the user to verify that the instrument is working properly. The operational
check is carried out in a similar fashion as the standard test but always with the calibration pad in place on a smooth concrete
surface. The pad is not used for normal testing but only when making an operational check.
It is suggested to make an operational check:
• Upon receipt of the instrument before any testing
Also, it is useful to make an operational check
• When results are not in accordance with expected results
• If the instrument has experienced some trauma
OPERATIONAL CHECK PROCEDURE
To determine the calibration pad value for the first time, carry out a modified Clegg Impact
Test procedure to obtain six readings on a suitable surface, preferably one that is at an easily
accessible “home” location. This same location should be used for all future operational
checks.
For a home site, select a firm solid base such as a bare concrete slab floor. Be sure that the
surface is smooth, dry and clean and that the surfaces of the calibration pad and hammer
strike face are dry and free of any foreign material. Place the pad under the guide tube such
that the hammer is centered on the pad. The pad must be between the hammer and floor.
The hammer must fully strike the calibration pad and not the floor.
Take the average of the six drops to obtain the calibration value. Note this average in a logbook
along with the tolerance of +/- 1 CIT units or 1.5 G’s. NOTE: There are 10 Calibration pad G’s
“gravities” per 1 CIT unit.
During future operational checks, make note of the value and tolerance on the calibration pad
and compare with measurements. The average reading should agree with the logged value.
Also mark or paint a line on the area of the concrete slab to show the area where the calibration
check will be performed. This way, the same area is used to ensure consistency.
Hammer Drop Procedure
The 2.5 kg model hammers may be dropped in two ways: Freehand or Plunger Release. Freehand is used for non-standard
drop heights. Freehand or Plunger Release can be used for standard drop heights.
FREEHAND
Leave the plunger pin retracted for all freehand hammer drops. To do this, pull back the knob on the hammer release spring
plunger until the plunger pin is fully retracted from inside the guide tube then rotate the knob 90 degrees to lock the pin
retracted.
For standard drop height, raise the hammer until the white line mark on the hammer, is even with the top of the guide tube.
Drops should be made with the mark within + 1/2 inch (1.25 cm) from the top of the guide tube.
Important – Perform Operational Check on test pad before first use of Clegg
Test Pad