Size calibration
Establish or adjust the relationship between instrument response and reference particle size.
Core distinction
Nominal size, certified mean and instrument response are different quantities
The number in a product name may be a target or nominal diameter. Calibration decisions should use the certified result for the lot and understand how the instrument converts particle interaction into a reported size.
| Term | Meaning | Decision consequence |
|---|---|---|
| Nominal diameter | Convenient target or catalog designation | Useful for search and ordering, not sufficient for calibration |
| Certified mean / peak | Lot-specific measured size result | Primary reference value for the procedure |
| Uncertainty | Quantified doubt associated with the stated result | Must fit the required measurement capability |
| CV or distribution | Spread of the particle population | Influences peak width and resolution testing |
| Optical-equivalent size | Instrument response relative to calibration material | Can differ for particles with different refractive index or shape |
Four jobs
Calibration, verification, count control and challenge are separate
Verification
Check that an existing calibration remains within acceptance criteria without necessarily adjusting it.
Count control
Evaluate repeatability or counting performance using a defined concentration.
Challenge testing
Introduce a controlled population to test efficiency, leakage or response under a specified method.
Commercial consequence: buying a higher concentration or broader size range does not make a product more suitable. It may make it wrong.
Selection sequence
A disciplined purchasing workflow
- Define the measurand and acceptance criterion.
- Identify the instrument method, medium and useful dynamic range.
- Select a particle family designed for the application.
- Choose available certified nodes that bracket or test the required response.
- Review uncertainty, CV, concentration and certificate scope.
- Validate sample preparation, handling and sampling.
- Record lot, expiration, storage and chain of use.
Applied Physics pathways
Current family-level decision map
20–900 nm aqueous PSL
Submicron size-calibration and research nodes.
Approximately 1–160 µm aqueous PSL
Micron and larger size-calibration nodes.
Count controls
Ready-to-use concentration pathways for liquid particle counters.
HEPA challenge material
Higher-solids material for filter challenge applications.
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.