Technical Information - Wavecom TnT ELB G4-Series User Manual

Wavecom Instruments Portable Appliance Testers Instruction Manual

Technical Information

Class 1 (Earthed Appliance) Definition
(Single basic insulated and protectively earth equipment)
This type of product design provides two safety barriers between all live conductors at dangerous voltages and
the equipment user.
The provision of basic insulation between exposed metal parts and live parts is the first barrier to provide basic
protection against electric shock.
The second safety barrier is by the connection of exposed (accessible) conductive (metal) parts to the protective
earthing conductor (earth wire) in the fixed wiring of the device/Installation.
The protective earthing terminal of the equipment must be marked with the word "earth" or the symbol "E" or the
symbol for Earth Terminal or Protective.
To perform this test a continuous earth loop must be made between the exposed conductive material (metal) and
the TnT appliance tester. This is done by means of connecting the earth lead with the crocodile clip/probe attached
to a GOOD earth point (paint & coatings will not provide effective connections) and the DUT (Device Under Test)
plugged into the TnT appliance testers' DUT socket. The Maximum allowable limit is less than1.0 (ohm).
Class 2 (Double Insulated) Definition
(Double insulated equipment)
This method of construction employs two safety barriers comprising two layers of insulation between
dangerous voltages and the user of the equipment.
The first layer of insulation is formed around the live conductor and is termed 'the Functional Insulation'.
The second layer of insulation is termed 'the Supplementary Insulation'. In Class II equipment, protection against
electric shock does not rely on basic insulation only, but has additional supplementary insulation such as double
insulation or reinforced insulation provided, there being no reliance on precautions in the fixed wiring of installation.
Class II equipment is marked with the words "DOUBLE INSULATION" or the symbol
For double insulated under Safety Symbols:
Note 1 – Double Insulation is insulation comprising both basic and supplementary insulation.
Note 2 – Reinforced Insulation is a single insulation system with a degree of protection against electric shock,
which is equivalent to double insulation.
Testing of Electrical Equipment
Many testing personnel have some reservations in testing sensitive, electronic equipment using a 500V DC
insulation test. There is a perceived fear of causing internal damage from over voltage. With the introduction on
the TnT Range of appliance testers, these concerns are alleviated.
The TnT Range of electrical portable appliance testers is safe to test electronic equipment as the tests are carried
from Active-Neutral (shorted by a relay inside the tester) to Earth. No dangerous voltages pass through in this
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