KYORITSU KEW3125A - Measurement Categories Explained; Understanding Over-voltage Categories

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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
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