IAI America ERC2 - Manual (Page 33)

1. Overview
14
Diode
(2) Noise sources and elimination
Among the numerous noise sources, solenoid valves, magnet switches and relays are of particular concern
when building a system. Noise from these sources can be eliminated by implementing the measures
specified below.
[1] AC solenoid valves, magnet switches and relays
Measure: Install a surge absorber in parallel with the coil.
[2] DC solenoid valves, magnet switches and relays
Measure: Install a diode in parallel with the coil. Determine the diode capacity in accordance with the load
capacity.
In a DC circuit, connecting a diode in reverse polarity will damage the
diode, internal parts of the controller and/or DC power supply, so exercise
due caution.
m Point
Install a surge absorber to each coil over a minimum wiring
length.
Installing a surge absorber to the terminal block or other part
will be less effective because of a longer distance from the coil.
Surge absorber