INFICON 2020ComboPRO Portable Photoionization Detector - Manual (Page 41)

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Recorded data can be reviewed on the display or downloaded to a computer. Data
are recorded by date and time.
The 2020ComboPRO has 5 keys for instrument operation. The keys are used to set
up and calibrate the 2020ComboPRO. All information entered with the keys and
stored in the 2020ComboPRO’s memory is retained when the instrument is switched
off. The clock and calendar continue to operate and do not need to be reset when the
2020ComboPRO is turned on.
General Operation
The 2020ComboPRO is a microprocessor-controlled air monitor for measuring the
presence of photoionizable compounds in air at parts-per-million levels. The block
diagram in Figure 2 shows the main components of the 2020ComboPRO.
Figure 2. The 2020ComboPRO Block Diagram
The microprocessor controls the components of the instrument and interprets and
records the signal generated by the photoionization detector (PID). Recorded data
and setup information entered into the microprocessor’s memory are retained when
the 2020ComboPRO is turned off.
A pump continuously pulls the air under test through the 2020ComboPRO’s PID.
The PID converts the concentration of photoionizable compounds in the sample into
an electrical signal. The microprocessor subtracts any background from the signal
and divides this signal by a sensitivity obtained by calibrating with a standard gas of
known concentration. This concentration appears on the 2020ComboPRO’s display
and, depending on the values entered through the 2020ComboPRO’s keypad, an
alarm status may be displayed and an audio signal may be heard.
The 2020ComboPRO can detect thousands of different types of airborne gases and
vapors and its response depends on the characteristics as well as the concentration of
each compound.
Inlet
Filter
Photoionization
Detector
Sample In Sample Out
Display and
I/O Connector
Keypad
Microprocessor
Power
Supply
Electrical Connections Gas Connections
Pump