KYORITSU 5406A - Page 6

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○Measurementcategories(Over-voltagecategories)
Toensuresafe operationof measuringinstruments,IEC 61010 establishes
safety standards for various electrical environments, categorized as O to
CAT.IV, and called measurement categories. Higher-numbered categories
correspond to electrical environments with greater momentary energy, so
a measuring instrument designed for CAT.III environments can endure
greatermomentaryenergythanonedesignedforCAT.II.
O : Circuitswhicharenotdirectlyconnectedtothemainspowersupply.
CAT.II :Electrical circuits of equipment connected to an AC electrical
outletbyapowercord.
CAT.III : Primaryelectricalcircuitsoftheequipmentconnecteddirectlytothe
distributionpanel,andfeedersfromthedistributionpaneltooutlets.
CAT.IV :The circuit from the service drop to the service entrance, and
to the power meter and primary overcurrent protection device
(distributionpanel).
O: Device which is
not directly
connected to the
mains power supply