HT instruments HT8100 - Manual (Page 4)

HT8100
EN - 3
1.2. DURING USE
Please carefully read the following recommendations and instructions:
CAUTION
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.
 Before activating the rotary switch, disconnect the test leads from the circuit under test.
 When the instrument is connected to the circuit under test, do not touch any unused
terminal.
 Avoid measuring resistance if external voltages are present. Even if the instrument is
protected, excessive voltage could cause a malfunction of the instrument.
 While measuring, if the value or the sign of the quantity being measured remain
unchanged, check if the HOLD function is enabled.
1.3. AFTER
USE
 When measurement is complete, set the rotary switch to OFF to turn off the instrument.
 If the instrument is not to be used for a long time, remove the batteries.
1.4. DEFINITION OF MEASUREMENT (OVERVOLTAGE) CATEGORY
Standard “CEI 61010-1: 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, reads:
(OMISSIS)
Circuits are divided into the following measurement categories:
 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.