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C200
H
ARDWARE
Instruction Manual C200 Part1 A1.doc
optek Danulat GmbH
•
D-45356 Essen
•
Germany
page 16
4.2 Relay
Contact
Protection
and Interference Suppression
If the relays are used to switch loads on and off, the relay contacts can become eroded due to arcing. Arcing
also generates radio frequency interference (RFI) which can result in analyzer malfunctions and incorrect
readings. To minimize the effects of RFI, arc suppression components are required; resistor/capacitor
networks for AC applications or diodes for DC applications. These components can be connected either
across the load or directly across the relay contacts. The RFI components must be fitted to the relay
terminal block along with the supply and load wires – see drawings below.
For AC applications the value of the resistor/capacitor network depends on the load current and inductance
that is switched. Initially, fit a 100R/0.022µF RC suppressor unit as shown in fig. A. If the analyzer
malfunctions (locks up, display goes blank, resets etc.) the value of the RC network is too low for
suppression and an alternative value must be used. If the correct value cannot be obtained, contact the
manufacturer of the switched device for details on the RC unit required.
For DC applications fit a diode as shown in fig. B. For general applications use an IN5406 type (600V peak
inverse voltage at 3A).
For reliable switching the minimum voltage must be greater than 12V and the minimum current greater
than 100mA !
NC C NO
External
DC Supply
+
–
Relay Contacts
Load
Diode
A – AC Applications
B – DC Applications
NC C NO
External
AC Supply
L
N
Relay Contacts
C
R
Load
*