Preparation Before Measuring; Requirements For The Sample; The Surface Temperature Of The Sample Should Be Less Than 120 °C; The Sample Must Feature A Metallic Smooth, Ground Surface, In Order To Eliminate Erroneous Measurements Brought About By Coarse Grinding Or Lathe Scoring. The Roughness Of The Finished Surface Should Not Exceed 2 Μm - PCE Instruments PCE-2500 Bedienungsanleitung

6

Preparation before Measuring

6.1

Requirements for the sample

6.1.1 The surface temperature of the sample should be less than 120 °C.
6.1.2 The sample must feature a metallic smooth, ground surface, in order to eliminate erroneous
measurements brought about by coarse grinding or lathe scoring. The roughness of the finished
surface should not exceed 2 µm.
6.2

Requirements for the weight of the sample

For samples weighing over 5 kg and of compact shape, no support is needed.
Samples weighing between 2-5 kg, and also for heavier samples with protruding parts or thin walls,
should be placed on a solid support in such a manner that they do not bend or move by the impact force.
Samples weighing less than 2 kg should be firmly coupled with a stable support weighing over 5 kg.
For coupling purposes,
- the coupling surface between the sample and base plate should be flat, plane parallel and ground.
- A thin proper layer of coupling paste is to be applied to the contact surface of the sample.
- The sample should be firmly pressed against the surface of the base plate by moving it with a circular
motion.
- The direction of impact should be perpendicular to the coupling surface.
- For the coupling operation, the following prerequisites must be fulfilled:
- The contact surface of the sample and the surface of the base plate must be flat, plane parallel and
ground.
- The direction of the test impact must be perpendicular to the coupled surface.
- Minimum thickness of the sample for coupling (5mm).
Proper Coupling:
Proper coupling requires a little experience. Insufficiently coupled samples produce large variations of
individual measurements, L-values which are too low and the operation is characterized by a rattling
noise upon impact of the test tip.
Example for coupling a test piece with a base plate:
6.3

Requirement for the surface hardened layer of the sample

Surface -hardened steels and especially case-hardened steels produce L-values which are too low when
case-hardening depth is small because of their soft core. When measuring with impact device D/DL the
depth of the hardened layer should be no less than 0.8 mm.
Surface of the test sample should not be magnetic.
For test sample of curving surface with radius of curvature R less than 30mm, a small support
ring should be used.
Manual
8