Calibration is a comparison test between a reference device and a device under test in a known, stable temperature environment. Without regular calibration, your equipment can fall out of spec, provide inaccurate measurements, and threaten the quality of the equipment. Calibration maintains measurement accuracy, standardization, and repeatability to assure reliable results; whilst validation is the accompanying documentation confirming and proving that measurement’s accuracy.
Instrument calibration of your temperature monitoring device is not only a safety concern but also an economic consideration since the accuracy of temperature monitoring devices can also affect production and your bottom line. Temperature calibration involves the reliable, reproducible and documented comparison of a temperature monitoring device, sensor or data logger being tested with reference equipment. The referenced instrument is precise and undergoes regular checks in an accredited laboratory.
It is a widely accepted industry rule that calibration testing is done every one to two years or according to the manufacturer’s suggested timeline to ensure accuracy is still according to spec. Temperature monitoring devices can experience a “drift” over time, influencing their accuracy. As components age and usage increases, the risk of drift varies according to the temperature monitoring device type. It is best practice that product temperature monitoring equipment be calibrated daily before use. Also, you must calibrate new equipment upon receipt and before putting it into service. And did you know that thermometers dropped on the floor or used frequently require calibration more often? This testing ensures the device’s accuracy continues to conform to nationally and internationally accepted standards.
The calibration standard operating procedures can be accredited to ISO/IEC 17025 standards. To ensure reliability, regular audits and intercompany tests are hosted. ISO/IEC 17025 is the most important standard for calibration and testing laboratories worldwide. Laboratories accredited to this international standard have demonstrated that they are technically competent and able to produce precise and accurate calibration data, specifying general requirements for the competence to carry out calibrations.
The South African National Accreditation System (SANAS) is the official accreditation body for South Africa and the only national body responsible for carrying out accreditations in respect of conformity assessment, as mandated through the Accreditation for Conformity Assessment, Calibration and Good Laboratory Practice Act (Act 19 of 2006). SANAS accreditation certificates are a legal recognition by the Government of South Africa that an organisation is competent to perform specific tasks. SANAS provides formal recognition to laboratories to the international ISO/IEC 17025 standard for the competence of testing and calibration laboratories.
One can calibrate a device using several methods – which can be a little complex to grasp. Calibration labs use their experience, equipment, the inaccuracy of the device under test (DUT), and the time required to decide. The options include 2-point calibration and 3-point calibration.
A 2-point calibration is also known as a zero and span adjustment. To create an offset correction, it uses a single point to calculate the difference between the reference value and the DUT reading and requires pressurising the device to the top 20% of the range to get the span or second point reading. (Versus when done in the lower 20% of the transducer range for 1-point calibration.)
A two-point calibration is more accurate than a one-point calibration, but a 3-point calibration consists of a high, middle, and low check and thus grants you proof of accuracy over a more extensive range.
Calibration does not make sensors more accurate; instead, accuracy is inbuilt by design. So foremost, manufacturers pair robust calibrated temperature monitoring devices with a compatible algorithm. Then, technicians conduct instance tests to ascertain that the resulting measuring equipment is precise and satisfies the specifications and a validation certificate is often supplied with new equipment dispatched from the manufacturer.