HT instruments HT7051 - Manual (Page 4)

HT2055
EN - 3
1.2 DURING USE
Carefully read the following recommendations and instructions:
CAUTION
Failure to observe the warnings and/or instructions may damage the
instrument and/or its components or generate a danger for the operator
 Before selecting a new function, disconnect the measuring probes from the circuit
 When the instrument is connected to the circuit under test, never touch any unused
lead
 The auxiliary current probe can be subject to a higher voltage. Avoid the contact with
this probe during measurement
 Avoid measuring resistance with external voltages. Even if the instrument is protected,
as an excess voltage may cause instrument malfunctions
1.3 AFTER USE
When measurements are completed, turn off the instrument by pressing the ON/OFF key.
1.4 DEFINITION OF MEASUREMENT (OVERVOLTAGE) CATEGORY
Standard "IEC/EN61010-1: Safety requirements for electrical equipment for measurement,
control and laboratory use, Part 1: General requirements", defines what is intended for
measurement category, commonly known as overvoltage category. In § 6.7.4: Measuring
circuits, it reads:
Circuits are divided into the following measurement categories:
 Measurement category IV is for measurements performed at the source of a low-
voltage installation.
Examples are electric counters and measurements on primary devices protecting
against overcurrents and on ripple adjusting units.
 Measurement category III is for measurements performed on installations inside
buildings.
Examples are measurements performed on distribution boards, circuit breakers, wiring
harnesses, including cables, bars, junction boxes, switches, sockets of fixed
installations and appliances designed for industrial use and other equipment, e.g.
stationary motors connected to fixed systems.
 Measurement category II is for measurements performed on circuits directly
connected to the low-voltage installation.
Examples are measurements performed on household appliances, portable tools and
similar equipment.
 Measurement category I is for measurements performed on circuits not directly
connected to the MAINS.
Examples are measurements performed on circuits not derived from the MAINS and on
circuits derived from the MAINS provided with a special (internal) protection. In this
latter case, the stress caused by the transients is variable; therefore, (OMISSIS) it is
necessary that the user knows the appliance’s resistance to transients.