HT instruments HT9021 - Manual (Page 4)

HT9021
EN - 3
1.2. DURING USE
Always keep to the instructions contained in this manual.
CAUTION
Non compliance with the CAUTIONs and/or the instructions may damage
the tester and/or its components or injure the operator.
• Before changing the switch position, take off the clamp jaw from the tested conductor
or the electrical circuit in order to avoid any accident
• When the clamp is connected to the circuits to be tested, never touch unused terminals
• When testing resistors, do not add voltage. Although there is a protection circuit,
excessive voltage would cause malfunctioning
• Before measuring current, remove the voltage-resistance test leads
• When measuring current, any strong current close to the clamp jaw will affect the
accuracy
• When measuring current, always put the tested conductor in the middle of the clamp
jaw in order to obtain a more accurate reading
• If the reading value or the sign indication remains unchanged during the measurement,
check if the HOLD function is active
1.3. AFTER USE
• Once the measurements are completed, turn the rotary switch to OFF.
• If you expect not to use the clamp for a long time, remove the battery.
1.4. MEASURING (OVERVOLTAGE) CATEGORIES DEFINITIONS
The norm EN 61010-1: Safety requirements for electrical equipment for measurement,
control and laboratory use, Part 1: General requirements, defines what measuring
category, usually called overvoltage category, is. On § 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.