ADLINK LPCI-7250 - Manual (Page 46)

38 Appendix
Device Selection:
As a guide in selecting R and C,
X R: 0.5 to 1
Ω
per 1V contact voltage
X C: 0.5 to 1
μ
F per 1A contact current
Values vary depending on the properties of the capacitor C acting
to suppress the discharge the moment the contacts open. Resistor
R acts to limit the current when the power is turned on. Test to
confirm. Use a capacitor with a breakdown voltage of 200 to 300V.
Use AC type capacitors (non-polarized) for AC circuits.
Diode Circuit
This circuit is suitable for DC applications. The diode connected in
parallel causes the energy stored in the coil to flow to the coil in
the form of current and dissipates it as joule heat at the resistive
component of the inductive load. This circuit further delays the
release time compared to the RC circuit.
Device Selection:
Use a diode with a reverse breakdown voltage of at least 10 times
the circuit voltage and a forward current at least as large as the
load current.
Contact
Inductive
Load
Diode