Wavecom Instruments Fully Integrated Test N Print Unit - User Manual
7
Technical Information
Class 1 (Earthed Appliance) Construction
(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 TnP
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 TnP appliance
testers’ DUT socket. The Maximum allowable limit is less than1.0 (ohm).
Refer Page 7 on how to extend time to get a true earth connection (Unique Earth Bond Test Feature)
Class 2 (Double Insulated) Construction
(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 TnP Range of appliance
testers, these concerns are alleviated.
The TnP 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 mode to the internal
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