22
Specifications
(cont’d)
* Noise rejection is the ability to reject unwanted signals, or noise.
• Normal mode voltages are AC signals that can cause inaccurate DC measurements.
NMRR (Normal Mode Rejection Ratio) is a measure of the ability to filter out these
signals.
• Common mode voltages are signals present at the COM and + input terminals, with
respect to ground, that can cause digit rattle or offset in voltage measurements. CMRR
(Common Mode Rejection Ratio) is a measure of the ability to filter out these signals.
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.
