Table of Contents
Advertisement
...2 INSTALLATION
2.8 Relay Contact Protection and Interference
Suppression – Fig. 2.5
If the relays are used to switch loads on or off the relay contacts
can become eroded due to arcing. Arcing also produces radio
frequency interference (r.f.i.) which can cause instrument
malfunctions and incorrect readings. To minimize the effects of
r.f.i., arc suppression components are required; these are
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.
For a.c. 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)
115V Position
110V min. to 120V max. AC
50/60Hz
Mains
Transformer
F3 0.5A 250V AC (T)
Relay
Board
F2 5A 250V AC (F)
Solenoid Valves
and Heater
Indicators
Caution. The protective
earth
be connected
must
to terminal 16.
Internal
Interconnection
Cable Terminals
6
Mains Voltage Selector
110V to120V
220V to 240V
L
MAINS
N
INPUT
N/C
RELAY
C
N/O
N/C
RELAY
C
N/O
N/C
C
N/O
N/C
C
SERVICE
N/O
N/C
C
SAMPLE
HEATER
N/O
+
-
+
O/P 2
-
Interconnection Cable from/to
Microprocessor Unit and Instrument
Components (wet section)
Fig. 2.3 Location of User Junction Box Components
as shown in Fig. 2.5A. If the instrument malfunctions the value of
the RC network is too low for suppression and an alternative
value must be used. If the correct RC suppressor unit cannot be
obtained, contact the manufacturer of the switched device for
details of the RC unit required.
For d.c. applications fit a diode as shown in Fig. 2.5B. For
general applications use an alternative 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.
230V Position
220V min. to 240V max. AC
50/60Hz
1
User
2
Cable
CAL
Entry
Glands
OUT
OF
OUT
OF
Note. The mains and pump ON/OFF
switches are situated on the right
O/P 1
hand side of the junction box.
Caution. The AC power supply
External
ground cable
User
the earth (ground) stud
Connection
Terminals
Mains 'ON'
Indicator
MAINS
Mains
ON / OFF
Switch
OFF
MAINS
ON
Mains Fuse –
1A, 250V AC (T)
1A (T)
F1 250V
OFF
Pump
PUMP
ON / OFF
Switch
ON
Cable Gland
be connected to
must
.
Advertisement
Table of Contents
