Noise
attenuation (reduction) is a common feature of power conditioners.
Electrical noise reduction is measured in decibels (db). The db is a
logarithmic ratio of intensity or, in the case of electrical noise, the
amplitude of one noise voltage level to another. For example, a 40 db
reduction in noise means that the incoming noise is reduce by a factor
of 10,000. There are two types of reduced noise: common mode and normal mode. Common
mode noise exists between the ground and the neutral. Electronic
devices are most sensitive to common mode noise. A shielded isolation
transformer is very effective in reducing common mode noise. Normal
(or transverse) mode noise exists between the "hot" lines and the
neutral. Normal mode noise is generally also reduced with a shielded
isolation transformer. |