User Manual

34 ISP-074-575-P1D

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