Electrical conductivity in materials - Measuring technique

In order to measure the conductive properties of materials, different techniques are used dependent on the resistance:

At relatively high resistance an Agilent 4339B High Resistance Meter with an Agilent 16008B Resistivity cell is used. Using this equipment makes is possible to measure resistivity / volume resistance up to 4.0 E+15 Ohm cm and surface resistivity up to 4.0 E+15 Ohm.

At higher conductivity, where the contact resistance becomes significant, 4-point measurements are done with a Keithley 2400 SourceMeter to determine the resistivity in the materials. For measurements of surface resistance ring electrodes are used as described in the standards.

Measurements are usually done at well defined temperature (23 ⁰C) and humidity (RH = 50 %), which are the standard conditions for measurements according to ASTM D257-07, ASTM D4496-04, ASTM D991-89(2005) or IEC 60093. If one wishes to measure on protective clothing according to DS/EN 1149-1, the measurements must be done at a relative humidity of 25 ±5 %. These measurements are carried out in a climatic test cabinet where the temperature and humidity can be varied over a large range. Measurements at 12 % RH fulfilling the requirements in DS/EN 61340-5-1 can also be made there. In general, an increased amount of moist leads to higher conductivity, this makes relative humidity important to the result.

The methods described above are not limited to measurements on plastics and polymer materials; they are also well suited for materials with a comparable resistance, i.e. from about 0.01 Ωcm to 4.0 E+15 Ωcm. Furthermore, we are experienced in measuring the resistance of composites, rubber and textiles.


 

Part of the equipment for volume and surface resistivity measurements.

Agilent 16008B Resistivity Cell for measurement on flat samples Min. Ø50 mm, max. 120 mm x 130 mm

Work on conductive composite materials is carried out in two development projects, one on injection molded flow plates, Project – Collaboration with Danish Companies in Development of Fuel Cells  and one on Hard-wearing materials for extreme environments