Size response
You need a reference diameter to establish or check an instrument’s size response.
Step 1
Define the job
Count performance
You need a known particle number concentration and repeatable sample preparation.
Filter challenge
You need an aerosolizable population compatible with the filter-test method.
Wafer deposition
You need PSL suitable for deposition—or a finished wafer standard with specified pattern and count.
Step 2
Define the environment and medium
| Question | Why it changes the choice |
|---|---|
| Will particles remain in water? | Controls suspension compatibility, dilution and liquid-counter use. |
| Will particles be aerosolized? | Generator efficiency, residue, concentration and delivered distribution become critical. |
| Will particles be dried? | Drying can create residue, aggregation or a different delivered population. |
| Will particles be deposited on a wafer? | Deposition system, wafer size, surface and SSIS response define the workflow. |
| Is the matrix chemically complex? | Ionic strength, pH, solvents and surfactants can destabilize the suspension. |
Step 3
Define the evidence required
- Certified mean or peak diameter for the exact lot.
- Measurement method and stated uncertainty.
- Distribution metric such as standard deviation or coefficient of variation where needed.
- Particle concentration or solids content when the procedure depends upon it.
- Lot number, expiration, storage and handling requirements.
- Traceability statement that accurately describes the calibration chain.
Step 4
Match the family—not merely the diameter
Standard aqueous size family
Best when the primary requirement is a certified diameter in a water suspension.
High-concentration SSIS family
Best when the deposition system requires selected pre-mixed concentration nodes.
Ready-to-use count control
Best when routine counting repeatability is the primary objective.
Challenge-particle family
Best when the method needs high-solids aerosol challenge rather than calibration precision.
Step 5
Reject false equivalence
Do not substitute based only on nominal diameter. The same number can appear in products with different concentration, uncertainty, CV, bottle volume, certificate scope and intended use.
When the technical requirement is incomplete, use the requirement brief rather than guessing.
Applied Physics technical pathway
Match the standard to the measurement—not the other way around.
Send the instrument, medium, target size, concentration, certificate and packaging requirements to Applied Physics for a technical recommendation.