physics

Particle counter

Particle counter is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Particle counter rather than just read about it. In short: A particle counter is used for monitoring and diagnosing particle contamination within specific clean media, including air, water, and chemicals. Particle counters are used to support clean manufacturing practices in a variety of industrial applications.

Key takeaways

Particle counter belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Particle counter to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Particle counter from memory before moving on to harder problems.

Reference excerpt

A particle counter is used for monitoring and diagnosing particle contamination within specific clean media, including air, water, and chemicals. Particle counters are used to support clean manufacturing practices in a variety of industrial applications. Clean manufacturing is required for the production of many electronic components and assemblies, pharmaceutical drug products and medical devices, and industrial technologies such as oil and gas.

Technology Particle counters function primarily using the principles of light scattering, although other technologies may also be employed. Light scattering by particles use instrumentation comprising a high-intensity light source (a laser), a controlled media flow (air, gas or liquid) and highly sensitive light-gathering detectors (a photo detector). Laser optical particle counters employ five major systems:

Lasers and optics: A laser operates on a single wavelength, so the light source is consistent with constant power output to illuminate the particle sampling region. Controlled flow: The viewing volume is a small chamber illuminated by the laser. The sample medium (air, liquid or gas) is drawn into the viewing volume, the laser passes through the medium, the particles scatter (reflect) light, and a photodetector tallies the scattered light sources (the particles). Photodetector: The photodetector is an electric device that is sensitive to light, and when particles scatter light, the photodetector observes the flash of light and converts it to an electric signal, or pulse. An amplifier converts the pulses to a proportional control voltage. Pulse height analyzer (PHA): The pulses from the photodetector are sent to a pulse height analyzer (PHA). The PHA examines the magnitude of the pulse and places its value into an appropriate sizing channel, called a bin. The bins contain data about each pulse, and this data correlates to particle sizes. Black box: The black box, or support circuitry, looks at the number of pulses in each bin and converts the information into particle data. Light obscuration by particles works on the principle where the presence of particles blocks some of the light from the photodetector, typically through either absorbance or light scattering. The photodetector records the obscuration of light and converts this to an electrical signal, this signal is then correlated to a specific sized particle using a PHA as with the scattering description above. Direct imaging particle counting employs the use of a high-resolution camera and a light source to detect particles. Vision based particle sizing units obtain two dimensional images that are analyzed by computer software to obtain particle size measurement, images can be retained and replayed for additional analysis A Coulter counter is an apparatus for counting and sizing particles suspended in electrolytes. It is typically used for cellular particles. The Coulter principle, and the Coulter counter that is based on it, is the commercial term for the technique known as resistive pulse sensing or electrical zone sensing.

Detection methods There are several methods used for detecting and measuring particle size or size distribution — light blocking (obscuration), light scattering, Coulter principle and direct imaging. A high intensity light source is used to illuminate the particle as it passes through the detection chamber. The light blocking optical particle counter method is typically useful for detecting and sizing particles greater than 1 micrometre in size and is based upon the amount of light a particle blocks when passing through the detection area of the particle counter. This type of technique allows high resolution and reliable measurement. If light scattering is used, then the redirected light is detected by a photo detector. The light scattering method is capable of detecting smaller-sized particles. This technique is based upon the amount of light that is deflected by a particle passing through the detection area of the particle counter. This deflection is called light scattering. Typical detection sensitivity of the light scattering method is 0.05 micrometre or larger. However, employment of the condensation nuclei counter (CNC) technique would allow a higher detection sensitivity in particle sizes down to nanometre range. A typical application is monitoring of ultrapure water in semiconductor fabrication facilities. If light blocking (obscuration) is used the loss of light is detected. The amplitude of the light scattered or light blocked is measured and the particle is counted and tabulated into standardized counting bins. The light blocking method is specified for particle counters that are used for counting in hydraulic and lubricating fluids. Particle counters are used here to measure contamination of hydraulic oil, and therefore allow the user to maintain their hydraulic system, reduce breakdowns, schedule maintenance during no or slow work periods, monitor filter performance, etc. Particle counters used for this purpose typically use ISO Standard 4406:1999 as their reporting standard, and ISO 11171 as the calibration standard. Others also in use are NAS 1638 and its successor SAE AS4059D. If direct imaging is used, a halogen light illuminates particles from the back within a cell while a high definition, high magnification camera records passing particles. Recorded video is then analyzed by computer software to measure particle attributes. Direct imaging particle counting employs the use of a high resolution camera and a light to detect particles. Vision based particle sizing units obtain two dimensional images that are analyzed by computer software to obtain particle size measurement in both the laboratory and online. Along with particle size, color and shape analysis can also be determined. Direct imaging is a technique that uses the light emitted by a laser as a source to illuminate a cell where particles are passing through. The technique does not measure the light blocked by the particles, but rather measures the area of the particles functioning like an automated microscope. A pulsed laser diode freezes the particle motion. The light transmitted through the fluid is imaged onto an electronic camera with macro focusing optics. The particles in the sample will block the light, and the resulting silhouettes will be imaged onto the digital camera chip.

Matrices Applications of particle counters are separated into three primary categories:

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Particle counter

Start with the simplest possible case. Write down what Particle counter claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Particle counter before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Particle counter ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Particle counter

In research: Particle counter appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Particle counter in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Particle counter is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aerosols, Counting instruments, Meteorological instrumentation and equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Particle counter outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Particle counter” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Particle counter in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Particle counter means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Particle counter out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Particle counter in simple terms?

Why does Particle counter matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Particle counter?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Particle counter.