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...4 CONNECTIONS
4.2.4 Relay Contact Protection and Interference
Suppression – Fig. 4.3
To reduce the risk of instrument malfunction or incorrect
readings when switching inductive loads, suppression
components must be fitted across the relay contacts.
For a.c. applications, fit a 100R/0.022µF RC suppressor unit
(part no. B9303) as shown in Fig. 4.3A. If the instrument
malfunctions (incorrect readings) or resets (display shows
'88888') when the relays operate, a larger RC network is
required. Contact the manufacturer of the switched device for
details of the RC unit required.
For d.c. applications fit a diode, – see Fig. 4.3B. For general
applications use a 1N5406 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.
External
L
N
AC Supply
A – AC Applications
External
+
–
DC Supply
B – DC Applications
Fig. 4.3 Relay Contact Protection
8
NC C NO
Re ay Contacts
RC
Suppressor
Unit
Load
NC C NO
Relay Contacts
Diode
Load
4.3 Selecting the Mains Input Voltage – Fig. 4.4
Input voltages (230V or 110V) for the main analyzer p.c.b. and
the probe heater supply p.c.b. are selected by two switches
located on their respective p.c.b.'s.
Caution.
Both front panels are held in position by the
front panel screws only and are not
otherwise captive. When removing the
panels, ensure they are supported adequately.
Caution. Set both switches to the
same
position,
damage to the instrument may occur.
Unlock and carefully open the upper front
1
panel ensuring it is fully supported.
2 3 0 V
3
1 1 5 V
2
Offer the front panel up to the enclosure and reconnect
5
the ribbon cable.
6
Replace the upper front panel and lock securely.
Fig. 4.4 Selecting the Mains Input Voltage
otherwise
permanent
Identify the selector switch
on the main p.c.b. and
select the required mains
voltage for the main p.c.b.
Disconnect the front
panel ribbon cable at
the main p.c.b. end.
Identify the selector switch
4
on the probe heater
supply p.c.b. and select
the required mains
voltage.
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