Owner manual
3-45
IM DR232-01E
3
Installation and Wiring
3.11 Countering Noise
• Relay noise suppression
R
Dc external
power supply
Contact
Diode
connect to the relay
coil terminal (socket)
directly.
(
)
(
)
Relay
the relay coil rating must
be as low as possible.
<DC relay>
To prevent noise and protect the contact,
connect the diode to the relay coil terminal
directly.
In addition to the above measure, reduce
the rated voltage of the relay circuit as
much as possible for higher reliability.
It is necessary to choose a diode that
matches the relay. Generally, a diode
whose rated rectifying current is at least
three times the current flowing through
the relay coil must be used.
And the rated reverse voltage must be at
least three time the operating voltage.
(Note) Across the relay or solenoid coil, a counter-electromotive force is produced by an
inductive load. This phenomenon may damage the contact or, as the noise source,
cause a malfunctioning of the equipment, and have an unfavorable effect on the
entire system.
Surge suppresser circuit
connect to the
relay socket
terminal directly.
(
)
C
R
C=0.01 to 1µF
Must withstand a voltage
of at least three times
the operating voltage.
R=0.3Re to 1Re
Re=Relay coil's DC resistance
<AC relay>
If a relay contact is connectd to the input
of the system components, apply the
measure shown in the figure at the right
to the relay coil. Otherwise, a counter-
electromotive force produced across the
coil may be induced on the contact side
through the relay's internal coupling or
coupling between the lines, and may
cause a malfunctioning of the equipment.
• Others (isolation from noise source: for hot line measurement)
(Hot line)
Power transistor
(Vcc)
Wrap
At high temperatures
At low temperatures
Mylar isolation film
Adhesive copper
foil tape
Adhesion
Anti-Noise Measures for PC Connection
When connecting the instrument to a PC, it is recommended to apply ferrite cores (e.g.
ZCAT3035-1303 from TDK) to the interface cable as a noise countering measure. Apply a ferrite
core on both sides of the cable as shown below, when the noise persists, apply more ferrite cores.
Personal
computer
Ferrite core
Function
grounding
terminal