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.
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.
Fig. 4.3 Relay Contact Protection
Caution 1. The upper enclosure cover is not
hinged or captive when unlocked.
Caution 2. Both switches must be set to the
same position, otherwise permanent damage to
the instrument may occur.
230
230V
115V
11
5
115V
230V
11
5
Seperate enclosure
and cover
Disconnect the front panel
ribbon cable at the main p.c.b.
end
2
Offer the cover up to the enclosure and reconnect the
ribbon cable
5
Refit the upper enclosure cover and lock securely
6
Unlock and carefully remove
the upper enclosure cover. See
Caution 1
.
1
Identify the selector switch
on the main p.c.b. and
select the required
mains voltage for the
main p.c.b. See
Caution 2
.
3
Identify the selector switch
on the probe heater
supply p.c.b. and select
the required mains
voltage. See
Caution 2
.
4
Fig. 4.4 Selecting the Mains Input Voltage
NC C NO
External
AC Supply
L
N
Relay Contacts
Load
RC
Suppressor
Unit
NC C NO
External
DC Supply
+
–
Relay Contacts
Load
Diode
A – AC Applications
B – DC Applications
