Indiana Calibration Services

What is Calibration?

Calibration is qualitative determination of the errors of measuring device and where necessary, adjusting these errors to a minimum. It is a set of operations that establish, under specified conditions, the relationship between values of qualities indicated by a measuring instrument or measuring system, or values represented by a material measure or reference material, and the corresponding known values realized by standards. Calibration is performed in accordance with a definite procedure that compares the measurements performed by an instrument to those made by a more accurate instrument or a standard for the purpose of detecting and reporting, or by adjustment, errors met in the instrument tested.


The words "calibrate" and "calibration" entered the English language during the American Civil War, in descriptions of artillery. Many of the earliest measuring devices were intuitive and easy to conceptually validate. The term "calibration" probably was first associated with the precise division of linear distance and angles using a dividing engine and the measurement of gravitational mass using a weighing scale. These two forms of measurement alone and their direct derivatives supported nearly all commerce and technology development from the earliest civilizations until about 1800AD.

Purpose of Calibration

Instrument calibration is one of the primary processes used to maintain instrument accuracy. Calibration is the process of configuring an instrument to provide a result for a sample within an acceptable range.  Eliminating or minimizing factors that cause inaccurate measurements is a fundamental aspect of instrumentation design.

To ensure readings from an instrument are consistent with other instruments and to determine the accuracy of the instrument i.e. that it can be trusted for its observed/displayed measured value.

The value of calibration for industry

Calibration defines the accuracy and quality of your measurement. But just buying a certified, calibrated equipment is not the answer you need to service and maintain the calibration of your equipment throughout its lifetime for reliable, accurate and repeatable measurements. Accurate measurements play a vital role at each stage in development and manufacturing of a quality product for consistent and reliable performance. A reliable and accurate result brings confidence in you as well as in your product. The goal of calibration is to minimise the measurement uncertainty by ensuring the accuracy of your test equipment. Calibration quantifies and controls the errors or uncertainties of the measurement processes to an acceptable level. Repeatability is a great virtue of equipment even ahead of accuracy, which can be defined only by quantification. In today’s world of competition, the only differentiator for your product is quality, which cannot just be assumed. To produce quality products, you need measurements that are accurate, reliable and repeatable. Not only for all the manufacturing processes but also for R&D firms, it is necessary to use calibrated equipment  to ensure reliability of results. Correctly performed calibration increases the productivity, optimises resources, and assures consistency, comparability and compatibility of products, services and acceptability. The importance of calibration cannot be undermined by any user. When performing any type of measurement, you must have confidence in your results that they are accurate and within specifications. Testing and measurement with calibrated equipment brings this confidence and is a form of quality assurance.

Mere Adjustment is not calibration! Most users are always confused between calibration and adjustment. It is important for the user to understand the difference between the two. When you are experimenting in a lab, and you do not see a ‘zero’ reading when the equipment is not connected, you make ‘adjustments’ to remove the offset. This is not calibration. Calibration is process of parameters verification of any equipment against a well-known standard. Calibration report is a data that shows what parameters of the equipment are within the manufacturer specification or what are out of specification. It does not include adjustment of parameters that are out of specification. Adjustment is a procedure in which parameters are adjusted within the specification range and usually done by the manufacturer or user. Although most companies maintain high levels of standards, they need to calibrate the equipment regularly. Drift in accuracies over a period is unavoidable but can be detected in time, corrected mathematically and adjusted by calibration, i.e., by using  a reference or a standard equipment. All calibration labs do not have capabilities of adjustments and fine-tuning.

What is Traceability ?
Traceability in calibration is an unbroken chain of comparisons (all having stated uncertainities) with national and international superior standards i.e., the equipment  which is used as master should be calibrated with better accuracy master until the traceability reaches to National Physical Laboratory (NPL) or international standards.

Why measurements must be Traceable ?

  • Traceable measurements ensure the uniformity of manufactured goods and industrial processes.
  • To support equity in trade as well as compliance to regulatory laws & standards.
  • Essential to the development of technology.
  • To provide traceable calibration of test and measurement equipment is an ISO-9000 requirement (Purpose: With an eye to provide safety and fitness for use) to ensure that the products manufactured in one country will be acceptable in another on the basis of agreed to measurement standards, methods & practices)
  • Provides users with assurance of the confidentiality, validity and accuracy of the data provided while testing. 

Uncertainty- How accurate are your measurements?
The result of any measurement does not indicate true value, but only an approximation or estimate of the true value of the specific quantity. Therefore, the result is complete only when accompanied by a quantative statement of uncertainty.
Uncertainty is defined as how close the measurement result is likely to be to the true value with reference to the value assigned to the national prototype standard for that parameter with certain probability or confidence level.

  • This is expressed in quantitative aspect of measurement quality.
  • This means traceability is automatically established when measurement uncertainty is quoted.
  • Uncertainty of measurement determines the measurement capability of a measurement standard or a measuring equipment.

Calibration Interval-Validity Period.
For how long is your calibration certificate valid? Or how frequently you need to calibrate your equipment? This is a very subjective question. The answer depends on many factors like the type of the measuring equipment, usage of the equipment, man-handling and atmospheric changes that may influence the reading. In all the cases, these are variables. The simple answer to this question, although not a very helpful one, is “when it needs it”. The calibration cycle of the equipment depends on the sensitivity of the equipment, environmental condition, usage, etc. Hence the calibration cycle varies from six months to 36 months depending upon the type of the equipment. Usually, it is required to be calibrated after an interval of twelve months from the date of previous valid calibration and needs frequent recalibration. The user has to fix the periodicity after seeing the results for three to four consecutive calibrations. For example, if every year it is exactly the same or within limits, he can extend the periodicity. If every year it becomes worse and he has to adjust or write down the correction chart, he has to compress the schedule. If the equipment undergoes any kind of repair, it has to be calibrated after repair. Adequate records of the test data must be maintained over a period of time to draw support for extension of validity period.

Difference between calibration and validation

A calibration is a process that compares a known (the standard) against an unknown (the customer's device). During the calibration process, the offset between these two devices is quantified and the customer's device is adjusted back into tolerance (if possible). A true calibration usually contains both "as found" and "as left" data.

A validation is a detailed process of confirming that the instrument is installed correctly, that it is operating effectively, and that it is performing without error. Because a validation must test all three of these operational parameters, it is broken into three different tests: the installation qualification (IQ), the operational qualification (OQ), and the performance qualification (PQ). It is confirmation by examination and the provision of objective evidence that the particular requirements for a specific intended use are fulfilled.
Salient Features (Calibration)

National And International Traceability