What is a Particle Counter?
A particle counter is an electronic instrument that detects and counts airborne or liquid particles. Particles are detected using laser based optical systems that shine a powerful light through a detection chamber. The detection chamber has collection optics that produce a signal which is processed to determine particle quantity and size in a given volume. There are two main detection methods in common use:
- Light Scatter: As the particles pass through the detection chamber then light energy is either absorbed by the particle or reflected. Off axis electronic sensors measure how much light is scattered in order to calculate how many particles have passed through the chamber. Typically used for counting smaller particles in either air or liquid. eg 0.1 to 25µm diameter
- Light Obscuration: As larger particles pass through the detection chamber they directly obscure the laser light and the electronic sensor measures the drop in order to count the particles. Typically best for counting larger particles in liquids. eg 0.5 to 600µm diameter
What kinds of Particle Counter are there?
For normal pharmaceutical, electronics,aerospace and industrial applications there are two main types of particle counter:
- Air Particle Counter: Typically used in a classification and monitoring Cleanrooms or to order to detect particles in critical processes.
- Liquid Particle Counter: Typically used to monitor the size and quantity of particles in pharmaceutical products like liquids for injection. Also used to monitor the quality of hydraulic oil for industrial applications.
The Particle Counter for Air:
Most air particle counters are used in a cleanroom environment in order to count and size the particles in the air. Cleanrooms are widely used within the pharmaceutical, electronics and aerospace industry to carry out manufacturing under extremely clean conditions. In these environments it is very important to reduce contamination to a minimum. A small pump draws ambient air through the detection chamber and past the laser based optical sensor.
- Yield Maximization:In a cleanroom manufacturing semiconductor chips the yield can be significantly reduced if particles fall onto the surface and contaminate the silicon wafers. The particle counter is used to prevent expensive quality control problems. The manufacture of processor chips takes place in many stages over a period of weeks so it is important to prevent the contamination at each stage to minimize reductions in product yield due to particle contamination.
- Compliance with Regulations:The pharmaceutical industry has various regulatory agencies that establish, maintain and enforce regulations relating to particle monitoring in Aspetic Manufacturing areas. Failure of a regulatory “Audit” can result in fines, manufacturing shut downs and scrapping of entire manufacturing product runs. The particle counter is used to provide a profile of the particles present to comply with the regulations and to indicate any potential issue with contamination.
The Particle Counter for Liquid:
There are applications for a liquid particle counter in the pharmaceutical, medical devices, electronics, the hydraulic power industry. A sample of the liquid to be tested has to be introduced into the instrument. A small pump is used to draw the liquid into the detection chamber where the laser based optics are located. For pharmaceutical products it is important to be able to carry out the full test with only a very small sample in order to reduce the cost. For example the HIAC 9703+ can carry out a test with just 1mL of product and so reduces waste to the minimum.
- Complaince with Regulations - Liquids for Injection: To comply with USP <788> quality control procedures the manufacture of liquids for injection have to be regularly monitored. Particles in these medical products could have serious health impacts if injected into a patient.
- Contamination Control – Medical Devices: During the final step of artificial joint manufacture there is a thorough rinse process using ultra-pure water. The level of particle contamination in rinse water is monitored to ensure that the products will be safe when used with a patient.
- Quality Control – Electronics: Silicon wafers are routinely rinsed with ultra-pure water during the manufacture process. Again the profile (quantity and size) of the particles present in the rinse water is monitored to ensure that the wafers are ok for the next stage.
- Predictive Maintenance - Hydraulic Oil: When hydraulic oil becomes contaminated with particles it can very quickly reduce the efficiency and cause expensive damage to a hydraulic system.. Monitoring contamination of hydraulic oil can also be an indication of “wear and tear” of the equipment requiring investigation and possible servicing. Hydraulic oils and fluids used in aircraft, cranes, lifts, excavators and other industrial machines.
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