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33
6
INSTALLATION…
…6.3
Connections, General
6.3.1
Relay Contact Protection and Interference Suppression – Fig. 6.6
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 a.c. applications or diodes for d.c. 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 Fig 6.6.
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 (part no. B9303) as shown in Fig. 6.6A. 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. 6.6B. For general applications use an IN5406 type (600V peak inverse voltage at 3A
– part no. B7363).
✶
Note.
For reliable switching the minimum voltage must be greater than 12V and the minimum current greater than 100mA.
Fig. 6.6 Relay Contact Protection
NC C NO
External
DC Supply
+
–
Relay Contacts
Load
Diode
NC C NO
External
AC Supply
L
N
Relay Contacts
C
R
Load
A – AC Applications
B – DC Applications
Summary of Contents for AX411
Page 1: ...AX400 Series User Guide Model AX411 Dual Input Conductivity Analyzer ...
Page 53: ...51 NOTES ...
Page 54: ...52 NOTES ...