Dimensional reference
Assigned particle size, distribution, method and uncertainty.
Instrument-specific calibration
Separate dimensional evidence from optical-response evidence.
A silica particle can have a well-characterized diameter while still producing a method-specific optical response that must be qualified in the receiving instrument.
Optical reference
Response under a defined wavelength, medium, path, geometry and instrument configuration.
Concentration reference
Mass, volume or number concentration with an appropriate preparation and uncertainty chain.
Compatibility audit
Ask whether the method assumes PSL, silica or another material.
| Instrument/application | Compatibility questions | Verification |
|---|---|---|
| Liquid optical particle counter | Carrier, refractive response, coincidence, size thresholds and calibration procedure | Manufacturer method and response check |
| Airborne counter / aerosol instrument | Aerosolization, drying, residue, density, charge and optical response | Controlled aerosol generation and accepted standard |
| UV-Vis or turbidity method | Wavelength, path length, concentration range and multiple scattering | Reference curve under the actual matrix |
| Microscopy / image analysis | Contrast, threshold, magnification, pixel calibration and morphology | Reference grid/scale plus particle-image controls |
| Wafer inspection | Substrate, wavelength, recipe, deposition and algorithm | Finished wafer artifact and tool qualification |
Calibration design
Use a hierarchy of evidence.
- Confirm the instrument manufacturer’s accepted calibration or verification procedure.
- Define the material and response model.
- Select the particle size points and concentration range.
- Control sample preparation, container, background and mixing.
- Run blanks, repeats and appropriate independent checks.
- Document uncertainty and decision limits.
Questions engineers ask
Frequently asked questions
Can a silica particle standard calibrate any optical particle instrument?
No. The instrument method, optical architecture, medium, size range and manufacturer procedure determine whether the material is appropriate.
Is optical response traceability the same as dimensional traceability?
No. A traceable size value does not automatically establish traceability of instrument response, count or concentration.
Sources and verification
Technical basis
- NIST measurement protocols — Supports separating dimensional, optical and concentration measurands.
- NIST traceability policy — Defines traceability for specific measurement results.
- Applied Physics UV-Vis silica pathway — Commercial material to evaluate for defined optical work.
Commercial specifications should be confirmed against the current Applied Physics quotation, certificate, lot documentation and product page before purchase or protocol use.
Continue the research
Related technical guidance
Optical scattering
Define the particle-medium-wavelength system.
Silica vs. PSL
Check material assumptions in the instrument method.
Particle size standards
Audit the certificate evidence.
Applied Physics technical pathway
Need a particle specification reviewed?
Send the target size, medium, concentration, application, certificate requirements and shipping destination. Applied Physics can evaluate the appropriate silica family or custom pathway.