HT instruments SPEED418 - Manual (Page 6)

400 Series
EN - 5
 Avoid measuring resistance with external voltages; although the instrument is protected,
an excessive voltage may cause damage.
 While measuring current, place the clamp toroid as far as possible from the conductors
not involved in measurement, as the magnetic field they produce could interfere with
the measuring operations.
 During current measurement, place the conductor as much as possible in the middle of
the toroid so as to optimize precision.
 While measuring voltage, current, etc., if the value of the quantity being tested remains
unchanged, check and, if necessary, disable the STOP function.
CAUTION
The symbol indicates the charge level. When there are five bars
next to the battery symbol, it means that batteries are fully charged; a
decrease in the number of bars to "
" indicates that the batteries
are almost low. In this case, interrupt tests and replace the batteries
according to the indications given in § 11.2. The instrument is able to keep
data stored also with no batteries
.
1.3. AFTER USE
When measuring operations are completed, turn off the instrument by pressing and
holding the ON/OFF key for a few seconds. Should the instrument remain unused for a
long time, remove batteries and follow the indications given in § 3.4.
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:
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
.