Yokogawa In-Situ Gas Analyzer TDLS200 - Manual (Page 23)

4-4
IM 11Y01B01-01E-A 6th Edition :Feb 13, 2013-00
<4. ANALYZER COMPONENTS>
Watchdog Power Interrupts
The power output channels for microprocessors have control logic lines (TTL activated). These allow for
watchdog interrupt/reset functionality.
Alarm Relays
There are three alarm relay circuits on the board. These are capable of actuating Form C Single Pole Double
Throw (SPDT) relays. The three connections of each relay (Common, Normally Open and Normally Closed) are
routed through the board to field terminals.
The contacts are rated for a maximum of 1A @ 24VDC.
The pluggable field terminals are mounted on the lower edge of the board, just to the left side of
the DC power input terminals. The appropriate relay(s) is actuated when there is an analyzer
Warning, Fault and/or Level Alarm.
Remote Validation/ Remote Calibration Initiation
A validation/calibration routine can be initiated from a remote location (up to 300m away) using contact
closures. The Back Plane has circuitry such that it can monitor for a return voltage. The return voltage comes
from remote Volt Free Contacts (VFCs) at the customer DCS (or other control system).
The circuits include suitable protection against inadvertent shorting/grounding of the supply 24VDC or the
application of excess power to the monitoring circuit. There are three sets of remote contact monitoring circuits
on the Back Plane.
Valve Relays
There are three calibration valve relay circuits on the board. These are capable of actuating Form C SPDT
relays. The common pole is connected to 24VDC power and the normally open pole is routed to the field
terminal block. Digital ground is also routed to the terminal block TB3 as shown below.
Figure 8 - Calibration Valve Relay Diagram
FPGA
TTL out Relay Coil
Drive Circuit
Relay Coil
Relay
Contacts
24VDC to
C and to NO
24VDC
TB3
DGND
24VDC 12W max to
external solenoid valve
when relay is energized
NOTE; Use ferrite coil or
direction diode on TB6
wired outputs to prevent
switching spikes
24VDC to external
solenoid valve when
relay is engergized
Relay Coil
Relay
Contacts
24VDC to C
C to NO