Agilent Technologies 16451B, Operation Manual

Page: 67 / 149

Non-contacting
Electrode Method
(Air Gap Method)
This method accurately derives the dielectric constant from the
capacitance dierence between two measurements , without the test
material, the other with the test material. These two measurements
are made with the distance between the electrodes held constant.
This method is especially applicable for lm materials , highly
compressible materials (such as foam rubber), or soft materials . The
merits and demerits of this method are as follows:
Merits
Air lm (error caused by air gap between the electrode and the
surface of test material) does not cause error
It is not necessary to apply thin lm electrodes
Demerits
It is necessary to measure capacitance twice
Equation to derive the dielectric constant is complex
Principle
Figure 3-15 shows the schematic electrode structure for this method.
Figure 3-15. Non-contacting method (Air Gap method)
Operation 3-21