During Use; After Use; Measuring (Overvoltage) Categories Definitions - Tenmars TM-87 User Manual

1.2.

DURING USE

An improper use may damage the instrument and/or its components or
injure the operator.
• When 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 measuring circuits never touch any unused
terminal.
• When measuring resistors do not add any voltage. Although there is a protection
circuit, excessive voltage could cause malfunctioning.
• If during measurement the displayed values remain constant check whether the HOLD
function is active.
1.3.

AFTER USE

• After using the instrument turn it off.
• If you expect not to use the instrument for a long period remove the battery to avoid
leakages of battery liquids which may damage its inner components.
1.4.

MEASURING (OVERVOLTAGE) CATEGORIES DEFINITIONS

EN 61010-1: Safety requirements for electrical equipment for measurement, control and
laboratory use, Part 1: General requirements, gives a definition of measuring category,
usually called overvoltage category. Paragraph 6.7.4: Measuring circuits:
(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.
CAUTION
3
TM-87/TM-88