Yokogawa Extractive Oxygen Gas Analyzer TDLS220 - Manual (Page 18)

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
<4 ANALYZER COMPONENTS> 4-3
IM 11Y01B02-01E-A 4th Edition September 11, 2012-00
Calibration 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 3 - Calibration Valve Relay Diagram
Connections of each relay (Common and Normally Open) are routed through the board to field terminals.
The contacts are rated for a maximum of 1A @ 24VDC (or 0.5A @ 125VAC).
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 a calibration gas check valve is to be initiated.
Laser Temperature & Current Control
The board has two main laser control function circuits, temperature control and laser current control.
Board Temperature
The board has a temperature sensing chip/circuit that monitors temperature of the board inside the main
electronics enclosure. The sensor is located on the top edge of the Back Plane.
Analog I/O Board outputs the analyzer results and reads input process gas compensation values (pressure
and temperature). The board has power status LEDs as well as voltage test points for the input and output
channels.
• Output channels (three) are ranged 4-20mA. They can be assigned to measured values
Oxgen, Transmission or compensation signal re-transmission.
• Input Channels (two) are used by the analyzer to read active values for process gas
temperture and/or process gas pressure. These are application dependant and may or may
not be required inputs. There are two channels, one for temperature and one for pressure.
Each may be used to read 4-20mA signals that are isolated or to read and loop power (with
integral 24VDC) signals.
Optional Mini Display (4x20 VFD) mounts on the analyzer enclosure door. The display itself is an indus-
trial grade 4 line 20 character vacuum fluorescence display (VFD) that is self illuminating (i.e. no back light
required).