Agilent Technologies Nano Indenter G200 User Manual page 323

Theory 7
Figure 7-19Hardness vs Displacement into Surface for fused silica
2
The parameter S /P should remain constant with depth for bulk
materials. If the data trend up or down, as shown in Figure 7-20, the
proper frame stiffness should be determined as described in Frame
Stiffness and Area Function Calibration in Chapter 6, "Commonly Used
Procedures".
Figure 7-20Data indicate that frame stiffness requires calibration
Agilent Nano Indenter G200 User's Guide 7-26