In rooms with electronic devices (e.g. computers), it is essential to ascertain the electrical resistance of floor coverings. This property is one of the additional classification requirements of floor coverings.
The term electrical resistance is used when referring to the electrical voltage required to allow a specific current to pass along a conductor. The electrical resistance of a material describes its capability to impede the flow of current.
The horizontal and the vertical resistances of a conditioned test specimen are measured using a high-resistance meter and electrodes under a controlled atmosphere.
- Horizontal (or surface) resistance measurement relates to the electrical resistance of a floor covering when laid, measured on the surface of the covering between two electrodes. This characteristic is used to identify the transverse conductivity within the sheet of flooring, i.e. its capability to discharge electrostatic charges horizontally in the floor covering.
- Vertical resistance measurement is appropriate for evaluating a floor covering when unlaid, and is measured between the upper surface and the lower face opposite it. This vertical resistance characteristic is used to evaluate the capability of a floor covering to quickly discharge any electrostatic charge from its wear layer / usable surface underneath the covering.
The resistance to earth measurement is intended for in-situ measurements since the results depend on the quality of the electrical earth during the measurement.
- horizontal resistance or surface resistance is the electrical resistance measured between two electrodes placed on the surface of a floor covering
- vertical or "surface to back" resistance is the electrical resistance measured between the surface and the back of a floor covering
- resistance to earth is the electrical resistance measured between the surface of a floor covering and the earth and must be measured to evaluate the electrical insulating ability of the floor covering. One special requirement on the floor covering involves the so-called double stipulation - i.e. electrostatic insulating ability (electrical insulation to ground) in conjunction with simultaneous conductivity. These properties must be offered by a floor covering if it is to protect people who work with components at risk from electrostatic hazards while exposed to unprotected mains voltage.
From each sample cut three test specimens measuring (500 ± 50) mm × (500 ± 50) mm.