Prevention Methods - Honeywell UDC3300 Product Manual

9.3

Prevention Methods

Introduction
Built-in noise
rejection
Signal and power line
separation
Suppression at the
source
1/01
There are three ways to prevent electrical noise from interfering with the
operation of the electronic digital equipment.
• Built-in noise rejection
• Separation of signal and power lines
• Noise suppression at source
The first method is to design the digital equipment with a high degree of
noise rejection built-in. This includes housing the equipment in a case that
will provide shielding, liberal use of noise rejection filters and opto-
isolators, and the use of noise suppressors on potential noise sources
within the equipment itself. This, of course, is the responsibility of the
manufacturer who usually performs extensive laboratory and field testing
of newly designed digital equipment to insure the adequacy of its
immunity to noise. As a minimum requirement, the equipment should be
able to pass the tests outlined in the IEEE Standard 472-1974 (Surge
Withstand Capacity Tests).
The second method is to prevent noise from getting on the signal and
power lines that are connected to the equipment. This is achieved by
proper separation and shielding of those lines. In some cases, separate
power lines or special power line regulation or filtering may be required
for satisfactory electronic digital equipment operation. It is the
responsibility of the installer to follow good wiring practices.
The third prevention method is to suppress the noise at its source. This is
the most effective but also the most difficult because it is not easy to
identify all of the potential noise sources in a typical industrial
installation. Therefore, "suppression" is usually a last resort for those
extreme situations where the other methods are insufficient by themselves.
See Noise Suppression at Source which follows.
UDC3300 Limit Controller Product Manual 97