By the term “tool” we mean any physical item that can be used to achieve a goal, especially if the item is not consumed in the process. Informally the word is also used to describe a procedure or process with a specific purpose.
A very big part of electrical calibration procedures consists of DC and Low Frequency (LF) measurements. Multimeters, resistors, power supplies and electrical testers are commonly used instruments that require periodical calibration. Voltage, current, resistance, inductance, capacitance, time and frequency are the principal quantities regarding DC and LF measurements. The Volt (V), the Ohm (Ω) and the Ampere (A) are examples of the basic units used for electrical measurements.
Metrology and calibration guides usually refer to the terms Measurement Standards and Measurement Traceability. Let us find out why these terms are important to metrologists and in what ways are related to one other.
Metrology is a science based on comparisons. A measurement of voltage, length, pressure or force must be compared to a well known and defined value, in order to produce a valid result. When performing comparisons, the existence of references for all measurement quantities is necessary. These references and their derived quantities are defined in the International System of Units (SI).
Calibration of gas meters has become a necessity nowadays. Several methods are applied for performing gas meters’ calibration. The most common ones are:
Gas meters can be divided into two categories: displacement meters and flow meters. Displacement meters measure volume directly through periodic filling and emptying of one or more measurement chambers. This is why displacement meters are considered to be volumetric meters. The most common displacement meters are:
Imagine we just finished the calibration of a resistor and the result of our measurement was 10.01 kΩ. Are we sure that this is the true value of the resistor? The answer is simple: No! We can never be 100% confident that we measured the true value. The true value could only be obtained by a perfect measurement, but such a measurement cannot exist. A doubt about our measurement result will always be there and this is the Uncertainty of Measurement.
UKAS (United Kingdom Accreditation Service) is recognized by the British government to assess the competence of organizations that provide certification, testing, inspection and calibration services, against internationally agreed standards.
We all know that test equipment is used to define a measurement of a parameter. Whether it is the temperature level of a pipe, the electrical charge running through a wire or even the moisture content in a building’s walls, specialist test equipment devices are able to accurately determine a measurement specific to that application.
If someone enters the term “ISO 17025″ in Google, they would probably find out that ISO 17025 is an International Standard with the title “General requirements for the competence of testing and calibration laboratories”. But what does this mean in practice?