HT instruments HT712 - Manual (Page 4)

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.