8
…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/0.022
µ
F 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.
Fig. 4.3 Relay Contact Protection
Fig. 4.4 Selecting the Mains Input Voltage
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.
230
230V
115V
11
5
115V
230V
11
5
Unlock and carefully open the upper front
panel ensuring it is fully supported.
Disconnect the front
panel ribbon cable at
the main p.c.b. end.
Identify the selector switch
on the main p.c.b. and
select the required mains
voltage for the main p.c.b.
Replace the upper front panel and lock securely.
Identify the selector switch
on the probe heater
supply p.c.b. and select
the required mains
voltage.
Offer the front panel up to the enclosure and reconnect
the ribbon cable.
1
3
4
6
2
5
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, otherwise permanent
damage to the instrument may occur.
NC C NO
External
AC Supply
L
N
Re ay Contacts
Load
RC
Suppressor
Unit
A – AC Applications
NC C NO
External
DC Supply
+
–
Relay Contacts
Load
Diode
B – DC Applications
