Yokogawa Extractive Oxygen Gas Analyzer TDLS220 - Manual (Page 17)

<4 ANALYZER COMPONENTS> 4-2
IM 11Y01B02-01E-A 4th Edition September 11, 2012-00
approx 5” W x 4” H (130mm x 100mm). A clear laminated safety glass window is mounted to the inside of
the door with stainless steel fasteners and a weather tight gasket. This allows for external viewing of the
actual display without opening the door. The right hand side of the door accommodates a keypad (30 keys,
stainless steel) which is also operated externally without opening the door.
Backplane Circuit Board
Large (approx. 10” H x 15” W) printed circuit board that mounts inside the enclosure. The board has
several integral circuits and several connectors to accommodate various plug-in boards. The board is
designed such that any field terminations are located along the lower edge of the board via pluggable
terminal blocks for customer or field cable interface.
All components and devices on the board are designed for extended temperature (-10 to +80ºC) and low
drift operation.
The Backplane Circuit Board contains the following integrated circuits:
• DC Power Input
• DC Power Distribution
• Watchdog Circuit
• Display Backlight Power Interrupt
• Alarm Relays
• Remote Calibration Initiation
• Calibration Valve Driver Relays
• Laser Temperature and Current Control
• Board temperature
DC Power Input.
There are four pluggable screw terminals located on the lower right hand side of the Back Plane. These are
used for connecting the 24VDC power input supply. These are factory configured to receive power from
the adjacent power supply enclosure. Therefore, the analyzer power input requirement is AC voltage and a
24VDC power supply is integrated to the analyzer.
There is an adjacent On/Off miniature toggle switch and re-settable thermal fuse.
The single 24DVC power supply is distributed to various output power channels. Each output power
channel has the appropriate DC-DC converter, regulator(s), filtering capacitors and status LEDs, etc. All
accessible voltages in the Control module are below 24V. A 65V, 10 mA power source is protected by a
cover with a “High voltage” warning sign.
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. We do not recommend applying AC voltage across these relay contact.
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. The Power off condition is the same as alarm condition i.e. they are powered in ‘normal’
(or no alarm) condition.
Remote Calibration Initiation
A 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.