Calmetrics Re-Certification Services

Properly maintained and calibrated thickness Standards are paramount to obtaining accurate, reliable results from thickness testing instruments. With over forty years of experience and service to the surface and metal finishing industries, Calmetrics Inc., is pleased to provide the following recommendations on Standards re-certification intervals and the underlying principles which helped establish the recommended intervals listed below:

• 1. We recommend foil standards used for XRF be recertified in one year intervals

  Foil standards are a practical means of calibrating thickness-gauging tools because of the non-contact nature of X-ray devices. The versatility of foils for handling multiple applications with the potential to reduce the overall cost of reference standards has made foils a very popular form of calibration standards. Calmetrics has taken great care to improve the durability of its foil standards through a combination of mounting & packaging enhancements, and the use of proprietary protective coatings. Nevertheless, foil standards are still fragile items since they are very thin. In some cases, they must withstand internal stresses common to some plated materials, and, depending on the type of standard, can become very susceptible to mechanical damage through handling and/or damage from environmental stresses.
  
  As such, it is not unusual for cracks or pinholes to develop over time, or for a foil to suffer significant damage due to accidental mishandling. Catastrophic damage is obvious, as is the necessity for replacement. However, small cracks or pinholes may not be readily noticeable. Though nearly microscopic in size, it is important to recognize that the size of the measurement beam of a typical XRF system is also nearly microscopic. Small cracks and pinholes can significantly affect a calibration if the X-ray beam is inadvertently positioned over the crack or hole in the foil. Calmetrics’ re-certification service of foils includes not only a uniformity test but also an inspection of the foil for microscopic cracks and pinholes that may adversely affect your calibrations and subsequent measurements.

• 2. We recommend plated (hard) standards used for XRF be recertified in two year intervals

  Since there is no contact with these standards during the calibration/measurement procedure, there is minimal potential for physical damage. Only accidental mishandling will cause significant damage. These type of standards are generally very stable with long life expectancies. Re-certification of these standards is recommended to assure that migration and intermetallics formed at the coating/substrate interface, or oxidation, all of which will occur over time for many coating/base combinations, do not significantly affect the X-ray thickness value originally assigned to that standard. Generally speaking, the above recommended re-certification intervals, when strictly followed, have historically provided our customers with adequate protection against erroneous measurements due to calibration errors caused by dysfunctional standards. However, standards usage and the degree to which they are cared for, will vary according to the user. Therefore, based on your own experience, with regular re-certification of standards, you may find it necessary to recertify your standards more or less frequently than the above recommendations suggest, in order to comply with your specific quality control requirements.

• 3. What ISO 17025 says about recertification cycles:

  ISO 17025 standard specifies the re-certification interval in section 5.10.4.4. This section states, “A calibration certificate (or calibration label) shall not contain any recommendation on the calibration interval except where this has been agreed with the customer. This requirement may be superseded by legal regulations”.
  
  This means you as the customer must inform us what the re-certification cycle should be. We have provided some recommended, general re-certification cycles above. But it is your responsibility to inform us of the re-certification cycle, if any, that is to be indicated on the certificate we supply. Your quality management system should have a means to specify these re-certification cycles. Generally, our standards are very stable and if handled with care, they do not need frequent re-certification. However, it may be good practice to start with a re-certification cycle as recommended by Calmetrics above and then, in cases where no problems are encountered during the re-certification process, you may consider extending the re-certification cycle based on positive historical data and experience. If however, you find your standards show damage often enough when returned to us for re-certification, you may want to consider increasing the frequency of re-certifications and/or reviewing your standards handling and storage procedures.

• 4. Brief Description of Recertification Procedure

  Initially, your standards are logged in when received and visually inspected under high magnification. At that point an assessment is made to determine if the standard integrity is sufficient for continued use or if it should be replaced because of detectable damage to it.
  
  The standard is then put through our re-certification process which involves calibrating an instrument using a set of “master” standards that are directly traceable to a set of certified, NIST traceable artifacts. The calibration involves long measuring times for maximum measurement confidence. After calibration, several measurements are taken across the surface of each of your standards, again using long measuring times for maximum, practical measurement certainty. The variation of these measurements is evaluated to determine thickness uniformity and the average of these measurements is compared to the labeled thickness of the standard to evaluate accuracy. If the standard is within specifications for thickness, uniformity, and accuracy, it is then considered re-certifiable. This procedure is almost identical to the procedure used to initially assign values to your standards when they were first calibrated. In other words, we treat your standard as if it were being calibrated for the very first time and compare our results to those of the initial calibration as indicated in our records and on your standard label.
  
  Additional actions we take while your standards are in our care include cleaning of dirty standards (where possible); replacement of worn, hard-to-read, labels; remounting of loose standards, no-charge replacement of damaged standards mounts and boxes, and/or replacement of badly damaged standards at discounted prices.

• 5. Summary of benefits of re-certification service

  a) confirmation that your standard has not physically changed either through misuse or internal/external factors that might affect it’s physical integrity.
  
  b) If a standard is found to be damaged or otherwise unfit for use, we offer replacements at significantly discounted prices compared to the prices of the same standards purchased for the first time.
  
  c) We provide the measurement data that is compared to previous measurement data. If new measurement data is within the allowable tolerances for thickness and/or composition of the standard, the standard is re-certified providing you with added assurance that its value(s) are valid.
  
  d) Calmetrics, as required by its own internal procedures reviews its master standards for accuracy at regular intervals. In this process, it is often true that additional master standards are added to the original set to provide further confidence in the master calibrations used to calibrate your standards. In addition, new, more accurate technologies may be available and used when making new supplemental master standards or otherwise validating a set of master standards. Or our research may reveal a better method of calibrating our XRF instruments for a specific application which results in more accurate measurements. The benefits of any of these improvements are directly transferred to your standard.
  
  We hope this information helps you better understand our standards re-certification procedure. Since your measurements depend on the quality of your standards, our standards re-certification program can provide you with valuable reassurance and confidence in your thickness-testing program. If you have any questions regarding standards or require an RMA number to return them, please feel free to call us at 631 580-2522 or send us an e-mail at: info@calmetricsinc.com, or contact our representative in your area.
  
  Please Note: The” Infinite” and “Base” standards often provided with Calmetrics’ calibrated thickness standards sets, do not require thickness certification. Certifications are normally provided only for thickness standards with plated films and/or compositions of alloy films. The base and infinite standards consist of essentially pure, bulk, elemental material with no coating. As such, the coating thickness associated with these standards is, by definition, either zero or “infinite” (thick enough so that x-ray intensity will not change as thickness is changed), depending on the application for which the standards are intended to be used. Since these values are assigned by definition and used only for reference to determine relative x-ray intensities, no thickness certification is required. However, a statement of conformance to some basic analysis of the material can be provided upon request.