INFICON 2020ppbPRO Portable Photoionization Detector - Manual (Page 39)

ISP-074-576-P1D 33
In Tag mode operation, the 2020ppbPRO prompts you to locate a site and then to
record a background and sample readings for the site. You can record up to 12,000
manual entries. There is no averaging of data in Tag mode.
Recorded data can be reviewed on the display or downloaded to a computer. Data
are recorded by date and time.
The 2020ppbPRO has 5 keys for instrument operation. The keys are used to set up
and calibrate the 2020ppbPRO. All information entered with the keys and stored in
the 2020ppbPRO
’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
2020ppbPRO is turned on.
General Operation
The 2020ppbPRO is a microprocessor-controlled air monitor for measuring the
presence of photoionizable compounds in air at parts-per-billion levels. The block
diagram in Figure 2 shows the main components of the 2020ppbPRO.
Figure 2. The 2020ppbPRO 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 2020ppbPRO is turned off.
A pump continuously pulls the air under test through the 2020ppbPRO ’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 2020ppbPRO
’s display
and, depending on the values entered through the 2020ppbPRO ’s keypad, an alarm
status may be displayed and an audio signal may be heard.
The 2020ppbPRO 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.
The 2020ppbPRO does not distinguish one type of compound from another,
but displays a number indicating the total concentration of all photoionizable
compounds in the sample.
Inlet
Filter
Photoionization
Detector
Sample In Sample Out
Display and
I/O Connector
Keypad
Microprocessor
Power
Supply
Electrical Connections Gas Connections
Pump