Gigahertz-Optik‘s Calibration Laboratory for Optical Radiation Measurement Quantities
Gigahertz-Optik’s calibration laboratory for optical radiation measurement quantities owns, uses and maintains lamp, detector and reflector based reference standards traceable to PTB, NRC, NIST and NPL.
1. Spectral Irradiance E(λ)
Spectral Irradiance E(λ) is the most basic radiometric measurement quantity and can be used to calculate many other quantities such as:
- Integral Irradiance E, associated with spectrally broadband detectors
- Photobiological Actinic Irradiance Ebiol
- Photosynthetically Active Irradiation EPAR
- Illuminance Ev
- Colorimetric Quantities
- Radiant Power, Radiant Intensity, Radiance, Luminous Flux, Luminous Intensity and Luminance for known geometrical relationships
The DAkkS/PTB proofed reference standard used here are 1000W FEL-type quartz-halogen lamps that have been carefully selected after a burn-in procedure of about 80 to 100 hours. The useful spectral range of these sources is 250 to 2500 nm. This type of calibration standard is also offered to our customers under the model number BN-9101 (refer to Calibration Standards & Uniform Light Sources chapter for more information).
2. Spectral Responsivity
Spectral Responsivity of optical radiation detectors is a commonly required calibration and is supplied with each Gigahertz-Optik detector order.
The DAkkS reference standard used in this type of calibration are Si–Photodiodes with its operating temperature controlled by a thermal sensor during the calibration procedure. The useful wavelength range of this reference detector is 248 to 1160 nm. Beside that NIST calibrated Si and InGaAs photodiodes are used for factory calibration in the spectral range from 200 to 1800 nm.
Calibrations other than spectral sensitivity and spectral irradiance are performed using calibration standards from NIST and other national labs. By intercomparison to the accredited DKD standards, long term stability and therefore traceability of the non-DKD standards is ensured.
ISO/IEC/EN 17025 (formerly ISO/IEC Guide 25, known as ANSI/NCSL Z540-1, and EN45001) accreditation assures the competency of calibration laboratories to carry out specific tests or calibrations and forms the basis of the lab’s quality system.
Traceability: an Unbroken Chain of Transfer Comparisons
Calibration is a prerequisite for maintaining accuracy in any type of measurement instrument. It is the foundation upon which subsequent measurements are based upon. Optical radiation calibration is typically done using the transfer method where the relationship between the reading of a device under test and that of a calibration standard is compared. The test device reading is then adjusted to that of the standard as needed, recorded and certified. Since this is a direct comparison qualification of this transfer standard is of the highest importance. A qualified standard should display an unbroken chain of transfer comparisons originating at a national standards laboratory. For example, the transfer standard of the national laboratory, primary standard (A) is used to calibrate the reference standard (B) at an accredited calibration laboratory. This reference standard is used to calibrate the laboratory work standard (C) to be used daily by the cal lab. This work standard is then used to calibrate the final product (D) or device under test. Accordingly, the calibration path is A-B-C-D. This path is called the chain of traceability. Each transfer device in the chain should be subjected to periodic examination to ensure its long term stability. The time span between examinations is typically set by the lab performing the calibration and is self-audited.
Accredited calibration laboratories guarantee recalibration cycle times for their standards plus a review of their calibration procedures since they are subject to annual review by an official accreditation authority.
For the optical radiation measurement quantities of Spectral Irradiance and Spectral Responsivity, the Gigahertz-Optik calibration laboratory offers DAkkS calibration with direct comparison to its reference standards and fully documented procedures. This type of calibration, which offers the lowest available calibration uncertainty, is normally requested by high level industrial calibration laboratories or institutions who may in turn use the calibrated device as theirown reference standard.
However, in the majority of applications, end-users only need a simpler more economically priced calibration, since their type of measurement may not demand the lowest possible measurement uncertainty. But they do demand calibration certificates showing a confirmed unbroken chain of traceability to a national standard. For this requirement Gigahertz Optik offers a „factory calibration“ for Spectral Irradiance and Spectral Responsivity and all other calibrations which do not require the higher accreditation level.
To confirm traceability, every calibration is documented by a calibration certificate, which lists the calibrated device‘s identification data, calibration procedure, calibration uncertainty, environmental conditions as well as the traceability data back to the national standards laboratory. The certificate is signed by the calibration engineer and stamped by the calibration laboratory manager.
The DAkkS ist the national accreditiation council in Germany. It is following the (EG) Nr. 765/2008 and the accreditation law (AkkStelleG) of Germany.
The basic idea of the DAkkS is to transfer as many PTB responsibilities to industry as possible, including the calibration of measurement and testing equipment. The DAkkS ensures the traceability of measurement and testing equipment to national standards by the accreditation and continuous control of industrial calibration laboratories (Gigahertz-Optik is accrediated as D-K-15047-01-00 by the DAkks).
Therefore, calibration carried out by DAkkS accredited calibration laboratories offers a secured traceable link to national calibration standards. An uninterrupted traceability chain of calibration to national standards is of critical importance for instrument and testing equipment manufacturers in order to be competitive in national and international markets and is absolutely necessary for any quality management system.
The qualification of the traceability to national standards is the job of the Physikalisch-Technische Bundesanstalt (PTB), the German national standard laboratory. The PTB will define, realize, keep and transmit the physical quantities of the SI-system, such as a meter, a second, a kilogram, a candela, etc.
To ensure objective results, equal standards must be used. The calibration of measurement and testing arrangements based on SI-units is a basis for correct, comparable, recognizable and therefore measurable values, which can be audited.
Within the DIN ISO 9000 standard the relationship between quality management and calibration are intertwined in part for continuous control of measurement and testing equipment.
Without exception, DAkkS accredited calibration laboratories fulfill the requirements of DIN EN ISO/IEC 17025 (general criterions to operate a testing laboratory). DIN EN ISO/IEC 17025 replaced EN 45001 and ISO/IEC Guide 25 in 1999.
The European position of the DAkkS is noted by its membership in the European Cooperation for Accreditation of Laboratories (EAL) in Rotterdam, which was founded out of the Western European Calibration Cooperation (WECC) and the Western European Laboratory Accreditation Cooperation (WELAC) in 1994. Within the EAL different national accreditation institutes cooperate with the goal of international acceptance of calibration certificates of the EAL-calibration laboratories. In November 2000, 34 accreditation institutions from 28 countries, including the PTB, the accreditation institution of the DKD, signed a Mutual Recognition Arrangement (MRA) of the International Laboratory Accreditation Cooperation (ILAC). More information about this arrangement and the participating countries is available online at
PTB - the German National Calibration Laboratory
The Physikalisch-Technische Bundesanstalt (PTB) is the highest technical authority for metrology in Germany. The PTB‘s responsibilities are to define, realize, keep and transmit the physical quantities of the SI-system, such as a meter, a second, a kilogram, a candela and many other standards.
The PTB is the official accreditation institution for DAkkS calibration laboratories such as the Gigahertz-Optik calibration laboratory for optical radiation measurement quantities. The PTB is also active in getting bilateral acceptance for international standards. Because of their activities in 1995, a Statement of Intent on Traceability of Measurement Standards was signed between the Physikalisch-Technische Bundesanstalt (PTB) and the National Institute of Standards and Technology (NIST) USA. The Equivalence of the National Standards of NIST and PTB for the SI Units of Luminous Intensity and Luminous Flux was officially recognized in April 1999.
More information is available on the internet at www.ptb.de
NIST - U.S. National Institute of Standards and Technology
As part of its responsibilities the Optical Technology Division of NIST's Physics Laboratory develops, improves, and maintains the national standards for radiation thermometry, spectroradiometry, photometry, colorimetry, and spectrophotometry; provides National measurement standards and support services to advance the use and application of optical technologies spanning the ultraviolet through microwave spectral regions; disseminates these standards by providing measurement services to customers requiring calibrations of the highest accuracy and performs research and publishes technical reports & procedures to further the base of knowledge.
For more information visit the NIST Physics Laboratory Optical Technology Division Home Page, www.nist.gov
NPL - National Physical Laboratory UK
NPL's Optical Radiation Measurement (ORM) Group provides services which are the backbone for optical radiation measurements in the UK and internationally. Here the UK's Primary Standards and scales are maintained, and research in measurement science is carried out.
ORM anticipates and responds to industrial and academic measurement requirements throughout the IR, Visible, and UV spectra.
Measurement and calibration services include the characterization and calibration of: all types of optical radiation sources, optical radiation detectors and associated devices, optical properties of materials and components & aspects of appearance including color, haze and gloss.
Visit NPL ORM Introduction Web Page www.npl.co.uk for more information.
NRC - National Research Council Canada
The NRC’s Institute for National Measurement Standards Photometry and Radiometry Group maintains photometric, radiometric, spectrophotometric and colorimetric standards, and provides associated, high-accuracy measurement services to industry, university, and government clients involved with lighting, transportation, manufacturing, telecommunications, public health and safety, and the environment.
More information is available on the internet at the NRC INMS Photometry & Radiometry Home Page: http://www.nrc-cnrc.gc.ca/eng/index.html