UNDERSTANDING CALIBRATION REPORTS
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UNDERSTANDING CALIBRATION REPORTS

INTRODUCTION

A calibration report, also known as a calibration certificate, is an important document containing essential information regarding equipment calibration and conditions. It is mainly used to report results of calibration. A calibration report should include details on out-of-tolerance conditions, along with any special measurement conditions. It also provides information on calibration correction.

There isn’t much debate around whether it’s important to have calibration testing done on your equipment. Many times it is required by an accrediting body. However, once you get the calibration report back, it can sometimes be confusing or difficult to understand what it all means.

In this whitepaper, we will cover what a calibration report is, what should be included in it, what it all means and what to do with the results.


WHAT IS A CALIBRATION REPORT?

To fully understand a calibration report, you first need to know what exactly a report is made up of. Below, we have listed some basic factors that should always be included in your calibration report.

  • The dates and environmental conditions at the time of calibration
  • The received condition of the equipment – including descriptions such as the ones below:
    • In-tolerance with description of meeting all specifications needed
    • Operational failure, with description of failure
    • Out-of-tolerance with out of tolerance description

  • The returned condition of the equipment – including descriptions such as the ones below:
    • In-tolerance with description of meeting all specifications needed.
    • Special specifications are met with description based off of customer’s request

  • A traceability statement
  • The standards used during calibration
  • The calibration procedure used on the equipment – this should also include a revision level if necessary
  • The calibration interval
  • Contact information for questions and concerns regarding the calibration report

Calibration reports should always be received after calibration, regardless of if you have accredited calibrations or traceable calibrations performed on your equipment. Depending on the application in which some equipment is used, you may be required to have such documentation on file for the said equipment at all times. It important to keep calibration reports up to date and organized. Each calibration report will have a serial number that associates one calibration with one instrument, therefore; it should be easy to keep calibration reports in order. This helps with audits and day-to-day functions.

WHAT TO LOOK FOR IN YOUR CALIBRATION REPORT

Proper understanding of a calibration report is critical. To best understand a calibration report, it is important to first know exactly what information should be included in the report and why. Below, we have created a list of what to look for in your calibration report and why it is significant.

BASIC INFORMATION

  • –this is an effortless, but very important part of a calibration report. The title helps to identify that the document is in fact a calibration report.
  • – every calibration report should include the name and the address of the calibration laboratory.
  • – a unique identification number should be always be present on a calibration report.
  • – while these seem like a given, it is extremely important to ensure that page numbers are included on your calibration report, along with page of the series it is. For example, page 4 of 5.
  • – customer’s name and address should always be included in a calibration report. This ensures that the right report is given to the right customer.

CALIBRATION INFORMATION

  • – a calibration report should include proper identification of the calibration method used during service.
  • – calibration reports should also indicate the condition of the equipment/tool being calibrated, along with a brief description of the equipment/tool for identification purposes.
  • – a calibration report should list the date of the receipt of the calibrated equipment/ tool. It should also include the date of the calibration.
  • – this one may be a given, but it is always important to ensure that a calibration report lists the calibration results and the unit of measurement.
  • – Knowing who worked on a certain tool or performed a calibration is important. A calibration report should include the names, functions and signature of the personnel authorizing the calibration report.
  • – specific information on calibration conditions, e.g., environmental conditions, should be included in a calibration report. Notably, this should section should contain information on the environmental conditions under which the calibrations were performed, especially if they influenced measurement results.
  • – A calibration report should always present evidence of measurement traceability to SI units of measurements.

UNDERSTANDING THE RESULTS OF YOUR CALIBRATION

After receiving calibration results, it’s important to review the calibration report to ensure accuracy. When reviewing the results, the following checkpoints should be concentrated on:

CORRECTION OF ERROR

This checkpoint is very important in regards to measuring instruments and devices and helps to identify errors and tolerance. For example, during preventive maintenance, a correction factor is determined to and then inputted on the equipment being calibration to compensate or correct the errors displayed.

TOLERANCE

This checkpoint is particularly important for understanding the total allowable error within an instrument. Tolerance is typically represented as a +/- value. Notably, instruments can become deformed due to environmental changes that lead to material expansion and contraction. For this reason, it is extremely important to review the calibration results for this checkpoint to ensure you understand the tolerance and to be able to take the allowable error range into consideration.

AS FOUND/AS LEFT DATA

These checkpoints includes data for before an instrument was calibrated and after it has been calibrated. It’s important to check this data to ensure that the measurement value lies within the limit. If your data shows an allowable limit, then your measurement value is acceptable.

Another important factor to acknowledge when checking the “as left” and “as found” data is that the “as left” column will, in some cases, differ in adjustment due to the “as found” value being outside of an acceptable limit.

TRACEABILITY AND UNCERTAINTY

These checkpoints include determining if the calibration results have calculated an estimated uncertainty ratio and if the results are traceable. If an uncertainty ratio is calculated correctly then traceability of measurements can be guaranteed. This is because during uncertainty estimation, a laboratory’s best measurement capability (BMC) is incorporated, which is acquired from a higher laboratory standard.

WHAT TO DO WITH YOUR CALIBRATION REPORT RESULTS

If you’re sending your equipment in for calibration, it’s likely you know why it’s important. Calibrating your equipment can prevent injury to the persons operating the equipment or injury from bad results. When you receive a calibration report, it can sometimes be confusing. However, the information that is contained in these reports helps you to pass inspections with accrediting bodies, as well as know whether your equipment is safe to use. It is important to know why and how all this information is useful, so here’s what do with your calibration report results now that you’ve received them.

ACCURACY

One of the most important questions of instrument calibration is, “How accurate are my instruments measurements?” By analyzing the results on a calibration report, this question can be answered.

As previously mentioned, calibration results given on the calibration report may vary both in specific values and also in formats, but usually display the value of a standard and the results obtained when using the instrument to measure that standard. The calibration report will also display the calculation of the actual error of the instrument calibration and the correction value.

These results help display and maintain instrument accuracy and can be used for repair purposes or readjustment.

RELIABILITY

When using an instrument, it is important to ensure that the readings can be trusted. Unfortunately not all measurements will read perfectly; therefore, knowing that your instrument is reliable after calibration is crucial. A calibration report displays instrument reliability.

The results on the calibration report indicate the degree of accuracy of an instrument. A calibration report includes a measurement uncertainty ratio which helps to indicate if an instrument is drifting. If an instrument’s measurements are reading outside of the calibration reports given ratio, than the instrument has drifted out of calibration is not reliable.

TRACEABILITY

Calibration report results are most useful if they can be related to other measurements. Traceability helps companies to maintain manufacturing tolerances, which in turn helps companies trace their measurement to a specific standard.

Traceability is particularly important to ensure overall accuracy and reliability and aids in inspections.

UNCERTAINTY

Taking uncertainty into account helps to determine the accuracy of instrument measurements. A calibration report can be used to determine if an instrument is reliable and accurate by comparing instrument measurements to the uncertainty measurement ratio calculated on the report.

In conclusion, calibration report results can be used to determine the overall accuracy and reliability of an instrument and can also be used to help determine when an instrument needs to be recalibrated.

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