ISO 21178-2020 pdf free download – Light conveyor belts — Determination of electrical resistances.
This document specifies test methods for determining the electrical resistances of light conveyor beltsaccording to ISo 21183-1.The resistances are surface resistance, volume resistance perpendicularto the belt plane, and longitudinal and transverse volume resistance parallel to the belt plane. Thisdocument also specifies two test methods for determining the surface resistivity and the volumeresistivity.
2Normative references
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references,only the edition cited applies. Forundated references, the latest edition of the referenced document (including any amendments]) applies.ISO 18573,Conveyor belts —Test atmospheres and conditioning periods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and lEC maintain terminological databases for use in standardization at the following addresses:-ISo online browsing platform: available at https://www.iso.org/obp
—IEC Electropedia: available at http;://www.electropedia.org/
3.1 electrical surface resistance
quotient of a direct-current voltage applied between two electrodes on the same surface of a test pieceand the current between the electrodes
Note 1 to entry: It is expressed in ohms (n).
3.2 lectrical surface resistivity
measured surface resistance calculated to apply to a square
Note 1 to entry: It is expressed in ohms (Q) and the size of the square is immaterial.
3.3 electrical volume resistance
quotient of a direct-current voltage applied between two electrodes in contact with opposite faces of atest piece and the current between the electrodes, excluding current along the surface
Note 1 to entry: It is expressed in ohms (2).
3.4 electrical volume resistivity
measured volume resistance calculated to apply to a cube of unit sideNote 1 to entry: It is expressed in ohm metres (Qm).
5 Electrical surface resistances
5.1 Method A: Measurement of surface resistance, R OA , omni-directionally
5.1.1 Applicability
This method is applicable to belts which are electrically two-dimensionally isotropic in the plane of the belt.
5.1.2 Principle
An electric current of specified voltage is passed via electrodes through a suitably prepared test piece taken from the belt.
5.1.3 Apparatus (see Figure 1)
5.1.3.1 Sheet of insulating material, a little larger than the test piece.
5.1.3.2 Two cylindrical and coaxial electrodes (see Figure 1), with contact surfaces machined flat and polished, as follows.
5.1.3.2.1 Electrode 1, circular.
5.1.3.2.2 Electrode 2, annular.
5.1.3.2.3 Material of electrodes, either brass or stainless steel.
5.1.3.3 Ohmmeter, having a measuring range up to 10 10 Ω and accurate to within ±5 %.
5.1.4 Test piece
5.1.4.1 Material
Test piece material shall be new, unused (“virgin”), but shall not be tested sooner than five days after manufacture. It shall be free from contamination and superficial damage.
5.1.4.2 Dimensions
The test pieces shall be square, 300 mm × 300 mm minimum, and shall be cut from the full thickness of the belt.
5.1.4.3 Number
Three test pieces shall be taken. One test piece shall be taken from the middle of the belt, the other two test pieces shall be taken in the area between 100 mm to 400 mm from each of the belt edges. The test pieces shall be selected in accordance with Figure 2.
5.1.4.4 Cleaning
If necessary, clean both surfaces of the test pieces by rubbing with fuller’s earth (hydrated magnesiumaluminium silicate), for example, using a clean cloth. After cleaning away all traces of the powder, wipe the surface with a clean cloth moistened with distilled water and then dry with a clean cloth.ISO 21178 pdf download