Data Instruments | Instrumentation & Automation | Theory of Calibration & Validation

Instrument Calibration And Validation

Data Instruments is committed to ensuring that our customers can achieve the correct result. One of the fundamental component of our program to meet this goal is our extensive Instrument Calibration & Validation Service. This service covers a comprehensive list of analytical instruments, including all electro-chemical instrumentation systems.

Definition of Calibration :

Calibration is the determination of the accuracy of an instrument, usually by measurement of its variation from a standard, to ascertain necessary correction factors.

Calibration can also involve the act of adjusting equipment so that it performs in accordance with an established standard or specification.

The process of Calibration establishes, under specified conditions, the relationship between the values indicated by the measuring system, and the corresponding values of a quantity realised by a reference standard or working standard within specified accuracy and precision. Measurements are based upon International Standards which are traceable; meaning all readings for each calibration is logged and therefore traceable right down to the equipment used for the instrument calibration.

Instrument Calibration

To have full confidence in your analytical measurements it is essential that you can demonstrate that each component of the measuring system is functioning to specification. If any component of the measurement system does not meet this requirement, questionable results will be obtained. For conductivity measurement, the following must be verified:

The conductivity meter’s ability to correctly process both conductivity and temperature inputs correctly
The conductivity sensor’s ability to generate the correct output signal
The temperature sensor’s ability to generate the correct output signal
(this includes conductivity sensors with integral temperature sensors)

Data Instruments’ Technical Services Department have developed a conductivity calibration service that meets all of these requirements. This service comprises :

Use of certified, traceable electrical simulators and standards to verify that the conductivity meter is processing input signals correctly.
Comparison of the temperature probes performance with a certified reference thermometer
Calibration of the conductivity sensor using certified, traceable conductivity standards.
Verification of the correct performance of the conductivity sensor using certified, traceable control standards. The values of the control standards used can be selected to reflect your typical conductivity measurement ranges.

This service can be performed at your own premises; or alternatively you can send your conductivity meter to Data Instrument for calibration in our purpose-built Metrology Laboratory. Conductivity meter calibration should be performed at least once a year, but for critical applications a greater calibration frequency will be required to provide the required confidence in the analytical measurements.

Examples of problems that have occurred from not calibrating equipment :

A major manufacturer of premium golf balls didn't have their weighing scales checked because they were used for shipping purposes only. They shipped out large containers of balls based on a total weight. After a program of periodic calibration was finally implemented, they discovered that each bin contained 300 more balls than had been stated which was equivalent to a £500 loss per bin.

A manufacturing process used an oven with a calibrated temperature controller. After three months the controller was found to be inaccurate meaning that the actual temperature was substantially higher than specified. The quality and reliability of products made during the whole period were now in question and a costly product recall seemed necessary. Although it finally transpired that the error didn't adversely affect manufactured product, it took a month's work to prove it.

There are many more cases like these but the point is that it's not worth leaving your equipment to potentially be fine by not having it calibrated!

Instrument Validation :

Instrument Validation is a fully documented process that ensures that an instrument is working correctly. To have proven confidence in analytical measurements, each component that contributes to the overall quality of the result must be identified and quantified. Instrument Validation demonstrates that the measuring instrument is working correctly and hence does not have a detrimental effect on the quality of the analytical results.

It is a regulatory requirement for pharmaceutical companies to perform Instrument Validation on all new analytical instruments; but Instrument Validation is becoming increasingly popular in other industries that also require proof of the correct result. Instrument Validation requires detailed knowledge of the instrumentation system being validated and is therefore usually performed by the company supplying the instrument.

Data Instruments’ Technical Services Department are qualified to perform Installation Validation on an extensive range of conductivity meters. This service consists of 3 components :

Installation Qualification (IQ) – all of the instrumentation components are identified and checked against the manufacturer’s component listing. The working environment conditions are documented and checked to ensure that they are suitable for the operation of the instrument.
Operation Qualification (OQ) – each of the instrument’s function are checked to ensure that they conform to the manufacturer’s specifications. This includes the use of certified, traceable electrical simulators and standards to verify that the conductivity meter is processing input signals correctly.
Performance Qualification (PQ) – the performance of the conductivity meter for its routine analytical use is checked to ensure that this complies with its specification. The temperature sensor readings are compared with a certified reference thermometer. After calibration, the conductivity sensor readings are compared using certified, traceable control standards. Control Standards of similar values to the intended test samples must be used for PQ – Data Instruments’ extensive range of conductivity standards means that we are uniquely placed to offers meaningful PQ for all conductivity measurement applications. Data Instrument provide full documentation of the Installation Validation, including instrument specifications and certificates for all of the test equipment and standards used. This documentation demonstrates that the conductivity meter is appropriate for its intended use.

Instrument Re-Qualification

Instrument Validation should not be viewed as a one-off event – confidence in analytical results is required for the whole of the instrument’s working life. To ensure that this confidence is retained, the instrument validation process should be repeated at regular intervals during the instruments operational life.

Data Instrument offer a Re-Qualification service that meets these requirements. The difference between our Installation Validation and Re-Qualification services is that IQ is omitted for the Re-Qualification service. Re-Qualification should be performed at least annually and should be performed more frequently for applications whose test results have critical implications.