Thermo Scientific 146i, Instruction Manual

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System Description
Software
Thermo Fisher Scientific Model 146 i Instruction Manual 8-7
Back Pressure Regulator
Controls back pressure flow through the system.
Reaction Chamber
The reaction chamber is where the sample reacts with ozone and produces
excited NO
2
that gives off a photon of energy when it decays.
The reaction chamber is heated and controlled to approximately 50 °C to
ensure optimum instrument stability.
Pressure Regulator and
Gauge
Regulates and measures gas flow through the system.
Software
The processor software tasks are organized into four areas:
• Instrument Control
• Monitoring Signals
• Measurement Calculations
• Output Communication
Instrument Control
Low-level embedded processors are used to control the various functions on
the boards, such as analog and digital I/O and heater control. These
processors are controlled over a serial interface with a single high-level
processor that also controls the front-panel user interface. The low-level
processors all run a common piece of firmware that is bundled with the
high-level firmware and loaded on power-up if a different version is
detected.
Each board has a specific address that is used to identify to the firmware
what functions are supported on that board. This address is also used for the
communications between the low-level processors and the high-level
processor.
Every tenth of a second the frequency counters, analog I/O, and digital I/O
are read and written to by the low-level processor. The counters are
accumulated over the past second and the analog inputs are averaged over
that second. The high-level processor polls the low-level processors once per
second to exchange the measurement and control data.