CATEGORY BENEFITS
What are Viscosity Standards
A viscosity standard is a fluid with a certified viscosity value at defined temperatures. These values are established through controlled calibration procedures and include measurement uncertainty. Viscosity standards are used to confirm that instruments are performing correctly and producing reliable results.
Why Viscosity Standards Matter
Using certified viscosity standards allows laboratories to:
- Verify instrument performance
- Maintain traceability to national or international standards
- Demonstrate compliance during audits
- Compare results across laboratories Without reference standards, viscosity measurements cannot be reliably validated.
Certification and Traceability
Certified viscosity standards are typically produced and calibrated under:
ISO 17025 (calibration competence)
ISO 17034 (competence and consistent operation of reference material producers)
Certificates include viscosity values, uncertainties, serial number and batch idenfication.
How Viscosity Standards are used
Standards are used for:
- Calibration & verification of glass capillary viscometers
- Verification of automated viscosity systems
- Routine quality control checks
- Inter-laboratory comparisons The selected standard should closely match the expected viscosity range of the samples being tested.
Selecting Certified standards
This page explains the purpose and role of viscosity standards. For certified oils, viscosity ranges, and ordering options, visit:
Certified values are provided for kinematic viscosity, dynamic viscosity and density, together with uncertainties of measurement to consider, when you use viscosity standards to check. The uncertainty evaluation has been carried out in accordance with requirements specified by the United Kingdom Accreditation Service (UKAS). The following types of oil viscosity standards are available in the PSL Rheotek range:
- kinematic viscosity
- low temperature
- high viscosity
- dynamic viscosity
Tip
The most reliable verification of your work is achieved, when you use a viscosity standard that has a similar viscosity value as your production samples. For example, if your production sample is a diesel oil, which usually comes in at 2.7 mm2/s at 40 degrees C, the optimal viscosity reference standard is the S3. This has a nominal value of 3 mm2/s at 40 degrees C.
How to read the results
It is very unlikely that your result will be 100% identical to the certified value on the bottle of the viscosity standard. The quality manual in your laboratory will provide the data on the allowed tolerance band. If there is no tolerance band for verification with viscosity standards in the laboratory quality manual, you can refer to the acceptable tolerance bands listed in Annex A4 of the method document ASTM D445.
If the result is outside the tolerance band, the first thing to do is to run the viscosity standard again. The purpose of this is to establish whether the first result of the viscosity standard test was an outlier. If repeated measurements are still outside the tolerance band it is time to send the viscometer to us for recalibration or purchase a replacement.
FAQ
You asked, we answered
What is a certified viscosity standard?
A reference fluid with documented viscosity values and uncertainty.
How do I select the correct standard?
Select a standard close to your sample’s expected viscosity for best accuracy.
Do viscosity standards expire?
Yes, standards have defined stability periods and should be used within their certified validity.
How do I store my viscosity standards?
We recommend storing the viscosity standards away from direct sunlight at a cool and stable temperature. 20 degrees C or 60 degrees F is ideal.
Can I reuse the oil viscosity standard?
No, this is not possible. On completion of verification, the portion of the bottle used for the testing must be discarded. Oil viscosity standards are single use.
What is the traceability of the certificate of calibration?
Our laboratory is UKAS accredited and audited every year. Our work in viscosity calibration, production of reference materials and handling of reference materials is carried out under ISO 17025 and ISO 17034. Sample certificates of calibration are available on request.
What is the primary reference in kinematic viscosity?
The primary reference in kinematic viscosity is double distilled water at 20 degrees C. This has an internationally agreed viscosity of 1.0034 cSt or mm2/second.
CUSTOM SOLUTIONS
Do you need a custom product for your custom requirements?
We listen to customer challenges. Each PSL Rheotek viscometer system is configured for the owner. A wide variety of international test method protocols are readily available in the software. Company specific method protocols are also supported.
