RKI Instruments Digester Gas Monitor - Manual (Page 20)

14 • Internal Description Digester Gas Monitor Operator’s Manual
• AC Terminal Strip
The 3-point AC terminal strip is located above the controller terminal strip (see
Figure 5 on page 12). The AC terminal strip facilitates wiring connections to the AC
power source.
Relays
The Digester Gas Monitor includes eight channel relays and one common fail relay. It also
includes four common/channel relays which are factory set for operational use of the
Digester Gas Monitor. All the relays have single-pole double-throw (SPDT) contacts, also
known as form C contacts, and are rated for 10 amps at 115 VAC (resistive). The contacts
are available at the channel alarm terminal strip and are labelled NO (normally open), NC
(normally closed), and C (common).
Figure 6: Digester Gas Monitor Relay Allocation
Channel Relays & Fail Relay
The eight channel relays are above the channel alarm terminal strip (see Figure 5 on
page 12 and Figure 6 on page 14). These relays are dedicated to specific channels.
Figure 6 illustrates the allocation of the channel relays.
The fail relay is located above the channel relays. The fail relay is a common relay.
Common/Channel Relays
The four common/channel relays, relays A, B, C, and D, are above the common/channel
alarm terminal strip (see Figure 5 on page 12 and Figure 6 on page 14). These relays are
used in the operation of the Digester Gas Monitor and are not available for customer use.
Termination Jumper
A two pin header with a termination jumper installed is located near the top edge of the
main PCB to the right of the display cable connector. It is labelled “RS-485 Line
Terminator” on the PCB silkscreen. The jumper has no function unless the Digester Gas
Monitor is wired into a Modbus installation. See “Chapter 9: RS-485 Modbus Output” on
CH 4
Relay
2
Fail
Relay
Relay
A
CH 1
Relay
1
CH 2
Relay
2
AC Fuses
CH 4
Relay
1
Channel
Relays
Relay
C
CH 3
Relay
1
CH 1
Relay
2
Power Switch
Relay
B
CH 2
Relay
1
CH 3
Relay
2
Not Available for Customer Use
Relay
D