326 Keysight InfiniiVision 3000 X-Series Oscilloscopes User's Guide22 ReferenceMeasurement Category DefinitionsThe "Not rated for CAT II, III, IV" measurement category is for measurementsperformed on circuits not directly connected to MAINS. Examples aremeasurements on circuits not derived from MAINS, and specially protected(internal) MAINS derived circuits. In the latter case, transient stresses are variable;for that reason, the transient withstand capability of the equipment is made knownto the user.Measurement category II is for measurements performed on circuits directlyconnected to the low voltage installation. Examples are measurements onhousehold appliances, portable tools and similar equipment.Measurement category III is for measurements performed in the buildinginstallation. Examples are measurements on distribution boards, circuit-breakers,wiring, including cables, bus-bars, junction boxes, switches, socket-outlets in thefixed installation, and equipment for industrial use and some other equipment, forexample, stationary motors with permanent connection to the fixed installation.Measurement category IV is for measurements performed at the source of thelow-voltage installation. Examples are electricity meters and measurements onprimary overcurrent protection devices and ripple control units.Maximum Input VoltagesWARNING Use this instrument only for measurements within its specified measurement category(not rated for CAT II, III, IV). No transient overvoltages allowed.CAUTION Maximum input voltage at analog inputs135 Vrms50 Ω input: 5 Vrms Input protection is enabled in 50 Ω mode and the 50 Ω load willdisconnect if greater than 5 Vrms is detected. However the inputs could still be damaged,depending on the time constant of the signal. The 50 Ω input protection only functionswhen the oscilloscope is powered on.
