What principle do particle counters operate on?

• A. Size discrimination
• B. Conductivity measurement
• C. Light blockage
• D. Pressure difference

Answer: (C)

Particle counters primarily operate on the principle of light blockage. In this method, a beam of light is directed through a sample of liquid. As particles in the sample pass through the light beam, they obstruct (or block) the light, which can be detected and measured. The extent to which the light is blocked correlates with the size and number of particles present in the liquid. This technique allows for a precise and efficient means of counting and sizing particles, which is essential in various water treatment applications to monitor for contaminants and ensure water quality standards.

While size discrimination is also important to understand in the context of how particle counters function, the core mechanism that allows for detection and quantification is indeed the obstruction of light. Conductivity measurement and pressure difference do not pertain directly to the functioning of particle counters, as they measure different properties and are used for different purposes in water treatment processes.