Teledyne 9110EH - Nitrogen Oxides Analyzer - Manual (Page 196)

Theory of Operation Model 9110EH Instruction Manual
processing. All sensors are linearized in the firmware and can be span calibrated from the
front panel.
10.3.4. Relay Board
The relay board is the central switching and power distribution unit of the analyzer. It
contains power relays, valve drivers and status LEDs for all heated zones and valves, as
well as thermocouple amplifiers, power distribution connectors and the two switching power
supplies of the analyzer. The relay board communicates with the motherboard over the I
2 C
bus and can be used for detailed trouble-shooting of power problems and valve or heater
functionality. See Figure 11-4 for an annotated view of the relay board.
10.3.4.1. Heater Control
The M9110EH uses a variety of heaters for its individual components. All heaters are AC
powered and can be configured for 100/120 VAC or 220/230VAC at 50-60 Hz. The M200E
has five power relays, only some of which are used for the following circuits.
The two reaction cell heaters are electronically connected in parallel for analyzers at
100/120 VAC line power and in series for units configured for 220/230 VAC. One configura-
tion plug on the relay board determines the power configuration for the entire analyzer.
In order to operate efficiently, the NO
2
converter must be heated to 315˚C. An AC band
heater wrapped around the NO
2
converter cartridge contains two heater coils that can also
be configured with the above configuration plug. A thermocouple imbedded in the heater
measures the temperature and feeds a small voltage to the relay board’s thermocouple
amplifier, which, in turn, transmits the linearized analog voltage to the motherboard.
On units with IZS options installed, an additional set of AC heaters is attached to the IZS
oven. Some special M9110EH models may have other, non-standard heating zones installed,
such as a bypass manifold.
10.3.4.2. Valve Control
The relay board also hosts two valve driver chips, each of which can drive up four valves.
The main valve assembly in the M9110EH is the NO/NO
X
- Auto-zero solenoid valve component
mounted right in front of the NO
2
converter housing. These two valves are actuated with
12 V supplied from the relay board and driven by the CPU through the I 2 Z bus.
A second set of valves may be installed if the zero/span valve or the IZS option is enabled
in the analyzer. Specialty manifold valves may be present in the analyzer.
10.3.4.3. Status LEDs
Sixteen LEDs are located on the analyzer’s relay board to indicate the status of the
analyzer’s heating zones and valves as well as a general operating watchdog indicator.
Section 11.1.4.3 shows the states of these LEDs and their respective functionality and
location.
Special status circuitry monitors the communication between motherboard and relay board
and drives the red LED labeled D1 (watchdog LED). Should this LED ever stay ON or OFF
182 M9110EH Rev 0