Greenlee DM-500 Manuel D'instructions page 24

Specifications (cont'd)
* Noise rejection is the ability to reject unwanted signals, or noise.
• NMRR (Normal Mode Rejection Ratio) is the rejection of AC signals that can cause
inaccurate DC measurements.
• Common mode voltage is the voltage present at the COM and + input terminals, with
respect to ground. CMRR (Common Mode Rejection Ratio) is the rejection of these
voltages, which can cause digit rattle or offset in voltage measurements.
Per IEC1010 Overvoltage Installation Category
Overvoltage Category I
Equipment of Overvoltage Category I is equipment for connection to circuits in which
measures are taken to limit the transient overvoltages to an appropriate low level.
Note: Examples include protected electronic circuits.
Overvoltage Category II
Equipment of Overvoltage Category II is energy-consuming equipment to be supplied from the
fixed installation.
Note: Examples include household, office, and laboratory appliances.
Overvoltage Category III
Equipment of Overvoltage Category III is equipment in fixed installations.
Note: Examples include switches in the fixed installation and some equipment for industrial
use with permanent connection to the fixed installation.
Overvoltage Category IV
Equipment of Overvoltage Category IV is for use at the origin of the installation.
Note: Examples include electricity meters and primary overcurrent protection equipment.
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