Ht-instruments HT712 Manual do Utilizador Página 4

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HT712
EN - 3
1.2. DURING USE
CAUTION
An improper use may damage the instrument and/or its components or
injure the operator.
Before changing the range, first disconnect the test leads from the circuit under test in
order to avoid any accident.
When the instrument is connected to circuits never touch an unused terminal.
When measuring resistors do not add any voltage. Although there is a protection
circuit, excessive voltage would still cause malfunctioning.
If values remain unchanged on the display during measurement check if HOLD
function is on.
1.3. AFTER USE
Once measurements are completed turn off the instrument.
If you expect not to use the instrument for a long period remove batteries.
1.4. OVERVOLTAGE CATEGORIES - DEFINITIONS
EN 61010-1 (Safety requirements for electrical equipment for measurement, control and
laboratory use, Part 1: General requirements) defines what a measurement category
(usually called “overvoltage category”) is. At paragraph 6.7.4: Measuring circuits it says:
(OMISSIS)
Circuits are divided into the following measurement categories:
Measurement category IV is for measurements performed at the source of low
voltage installations.
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.
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