HT Instruments HT4020 Manual De Instrucciones página 35

1.2. DURING USE
Non compliance with CAUTIONs and/or instructions may cause damage to
the tester or its components or injure the operator.
• Remove the clamp jaw from the conductor or circuit under test before changing the
range.
• When the tester is connected to the measuring circuits, do not touch any unused
terminal.
• Do not measure resistance in the presence of external voltages. Even if the circuit is
protected, excessive voltage could cause the instrument to malfunction.
• When measuring current with the clamp jaws, first remove the test leads from the
instrument's input jacks.
• When measuring current, any other source near the clamp jaw could affect its
accuracy.
• When measuring current, always put the conductor to be tested in the middle of the
clamp jaw to obtain the most accurate reading as referred into § 4.1.2.
• While measuring, if the value remains unchanged check if the HOLD function is
enabled (H symbol at display)
1.3. AFTER USE
• After taking measurements turn off the clamp
• If the instrument is not be used for a long period, remove the battery
1.4. DEFINITION OF MEASURING (OVERVOLTAGE) CATEGORY
The norm IEC/EN61010-1: Safety requirements for electrical equipment for measurement,
control and laboratory use, Part 1: General requirements, defines what a measuring
category, usually called overvoltage category, is.
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 in the building installation
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 norm requires that the transient withstand capability of the
equipment is made known to the user.
CAUTION
EN - 3
HT4020 - HT4022