Pid Theory - MSA Sirius Mode D'emploi

Chapter 2,
PID Theory and Definitions
To support the safe and effective operation of the Sirius Multigas
Detector, MSA believes operators should have a working knowledge of
how the instrument functions, not just how to make it work. The
information presented in this section supplements the hands-on
operational instruction provided in the rest of the manual for the PID.

PID Theory

A photoionization detector (PID) uses an ultraviolet lamp to ionize the
compound of interest. A current is produced and the concentration of
the compound is displayed in parts per million on the instrument meter.
Figure 2-1. Typical Photoionization Sensor Design
2-1