HT instruments HT9 - Manual (Page 4)

HT6-HT8-HT9
EN - 3
1.2. DURING USE
Please carefully read the following recommendations and instructions:
WARNING
Failure to comply with the caution notes and/or instructions may damage
the instrument and/or its components or be a source of danger for the
operator.
 When the instrument is connected to the circuit being tested, do not touch any unused
terminal.
 Avoid measuring continuity if external voltages are present.
1.3. AFTER
USE
 If the instrument is not to be used for a long time, remove the batteries.
1.4.
DEFINITION OF MEASUREMENT (OVERVOLTAGE) CATEGORY
Standard CEI 61010: Safety requirements for electrical equipment for measurement,
control and laboratory use, Part 1: General requirements, defines what measurement
category, commonly called overvoltage category, is. § 6.7.4: Measured circuits, circuits are
divided into the following measurement categories:
(OMISSIS)
 Measurement category IV is for measurements performed at the source of the low-
voltage installation.
Examples are electricity meters and measurements on primary overcurrent protection devices
and ripple control units.
 Measurement category III is for measurements performed on installations inside
buildings.
Examples are measurements on distribution boards, circuit breakers, wiring, including cables,
bus-bars, junction boxes, switches, socket-outlets in the fixed installation, and equipment for
industrial use and some other equipment, for example, stationary motors with permanent
connection to fixed installation.
 Measurement category II is for measurements performed on circuits directly
connected to the low-voltage installation.
Examples are measurements on household appliances, portable tools and similar equipment.
 Measurement category I is for measurements performed on circuits not directly
connected to MAINS.
Examples are measurements 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 standard requires that the transient withstand capability of the equipment is made
known to the user.