ThermoFisher Scientific 146iQ, Инструкция по эксплуатации

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Introduction
Principle of Operation
Thermo Scientific 146iQ Instruction Manual 1-3
All of the components used such as mass flow controllers, ozone generator,
power supplies, solenoid valves, and photometer have been used previously
for calibration purposes, and are known for their accuracy and reliability.
In the 146iQ, these components are integrated into a single
microprocessor-controlled unit. The instrument can be controlled locally
via the front-panel interface or remotely, using a datalogger or computer.
The standard 146iQ hardware/plumbing configuration comprises gas and
zero air flow controllers, as shown in
Figure 1–2 . The basic unit can handle
six gas standards, controlled by individual solenoids. The zero air flow and
the gas flow are regulated by mass flow controllers. The zero air controller
is high flow (typically 10 slm full scale). The primary gas flow controller is
low flow (typically 100 sccm). An additional available gas flow controller
option would allow the user to dilute gas standards over a wider range than
allowable/achievable with a single span gas mass flow controller. When the
two gas flow controllers are installed, they are connected in parallel to the
same gas solenoid. The 146iQ turns on the gas flow controller with the
lowest flow rate that can accommodate the requested/calculated flow and
hence can provide the most accurate flow metering. When a flow is
requested/calculated that is higher than the highest range of the flow
controllers, but is lower than their combined maximum range, both gas
flow controllers are utilized. A PTFE mixing chamber is used to achieve
complete mixing of the two components at the desired concentration level.
This hardware/plumbing configuration allows precision gas dilution.
The 146iQ can be equipped with an optional internal ozone generator.
The hardware/plumbing configuration of the standard instrument with the
ozone generator is shown in
Figure 1–3 . The generator produces ozone by
exposing air to light at 185nm. The achievable ozone concentration is
changed by varying the intensity of the lamp and varying the zero air flow.
With all of the gas standard solenoids deactivated, the 146iQ can be used
as a transfer standard ozone-generating source.
Gas Phase Titration (GPT) is achieved by combining ozone with a known
NO concentration, and measuring the loss of NO using the NO channel of
a chemiluminescence analyzer. The amount of NO
2
formed is equal to the
measured decrease in the NO level, as shown in the following equation:

h O NO O NO
2 2 3
   
Principle of
Operation
Dilution
Ozone Generation
Gas Phase Titration