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UNI-T Multimeter
Art.no 36-7745 Model UT133B
Please read the entire instruction manual before using the product and then save
it for future reference. We reserve the right for any errors in text or images and any
necessary changes made to technical data. In the event of technical problems
or other queries, please contact our Customer Services (see address details on
the back).
Information about this measuring instrument
This multimeter has been constructed and tested in accordance with the requirements
of Measurement Category III (CAT III) up to 600 V nominal voltage and Pollution
Degree 2.
Categorisation
Measuring instruments are classified into categories according to what kind of
electrical environment they can be used in and how safe/protective they are at
withstanding overvoltages.
The Measurement Category of the instrument will be marked on the rating plate.
The Measurement Category indicates how capable the instrument is of withstanding
overvoltages which could be dangerous for the user.
In brief, the categorisation can be described like this:
• In the event of a sudden overvoltage on the power grid (a transient energy spike
from a lightning strike for example) the danger is greatest at the point where
the power supply service cable enters a building.
• Further in the building, the resistance (impedance) in the mains supply
cables increases and connected appliances and devices reduce and divide
the overvoltage. Therefore, the Measurement Category (also called Overvoltage
Installation Category) of the measuring instrument indicates which electrical
environment the instrument is designed to be used in.
The categories that measuring instruments are classified into are:
• CAT
I
: For measuring electronics and products that have a built-in protection
from overvoltage.
• CAT
II
: For measuring single-phase equipment connected to a household mains
supply, both through wall sockets and fixed installation.
• CAT
III
: For measuring electrical wiring installed in buildings. Examples are
measurements on fixed installation cables and hard-wired appliances, socket
outlets, circuit breakers and distribution boards. Three-phase distribution (all
supply cables and 3-phase equipment, machines and appliances).
• CAT
IV
: Three-phase at the utility connection and any outdoor conductors.
This multimeter is rated as CAT III and is approved for measuring voltages up to
600 V on single-phase products. This multimeter must not be used for measuring
three-phase equipment, three-phase cables or distribution boards even if
the nominal voltage is not higher than 600 V.
