Space charge measurement using the acoustic
technique has become a common method for investigating dielectric properties of
solid materials. The pulsed electroacoustic (PEA) method has been used for
various industrial applications, such as for the evaluation of ion conductive
materials. Typical PEA systems can measure space charge profiles in the
thickness direction of specimens, with the resolution of around 10 microns, at
the repetition rate of ms order.
This method was developed about 15
years ago by T. Maeno, and has been applied to various applications world wide.
At NICT (former CRL), there are high resolution, transient, 3-D, portable,
mountable and open PEA systems. We welcome students from universities, and some
innovative PEA systems have been developed by them at NICT.
This is the
simplest example of the charge measurement. When you put some charges
between two polystyren sheets, the charges stay there because polystyren
is a kind of good insulation.
Without voltage application, only induced
charges are observed on the both electrodes due to the accumulated charges
ih the middle. If you apply dc electric field from outside, surface charge
quantity changes but the charges in the middle don't.
[Induced charge due to dc bias; Q=CV]
When dc 5 kV is applied to a PS film sample, surface charges appear on
the both electrodes. Electric field and potential distribution can be
calculated easily from the observed charge distribution.
-- Works introduced in this website has been
done at NICT. --
(Last Update: August, 2004)