HT instruments M70 - Manual (Page 4)

M70
EN - 3
1.2. DURING USE
Read the recommendations which follow and the instructions in this manual:
CAUTION
An improper use may damage the instrument and/or its components or injure
the operator.
 Before selecting any function, first disconnect the test leads from the circuit under test
 When the instrument is connected to circuits never touch any unused terminal
 Do not measure resistance in presence of external voltages; although the instrument is
protected, an excessive voltage may cause malfunctioning.
CAUTION
If the “low battery” symbol is displayed during use interrupt testing and replace
batteries following the procedure described in § 5.2.
1.3. AFTER USE
 Disconnect the test leads from the circuit under test and switch off the instrument
 If you expect not to use the instrument for a long period remove batteries.
1.4. OVERVOLTAGE CATEGORIES - DEFINITIONS
Standard IEC/EN61010-1 (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 § 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 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.