What is Calibration?
This is an age-old question with many different answers, depending on who you ask. And for those of you who may be confused, go ahead, and stay confused. Because there really are numerous meanings of “Calibration”.
A simple definition of ‘Calibration’ when speaking of measuring instruments is to measure the accuracy of your instrument against instruments of known and higher accuracy, and adjust it as needed, to assure that it conforms to its specifications over its full range of operation.
Whenever an instrument makes a measurement of an internationally accepted value (such as volts DC or AC, Ohms, Hertz, centimeters, degrees Celsius, PSI, kilograms, etc.), calibration compares the accuracy of the measured or generated value of the instrument against those international units. And if your instrument does not match those units, it is adjusted until they match (although some instruments do not have the ability to be adjusted).
This is an important detail that many do not well understand. Whether you are measuring lengths to install a window, weighing produce at a grocer, pumping gasoline, monitoring steam pressure at a power plant, torqueing lug nuts on a tire of a car, or so many other examples, the instrument making the measurement must be right.
For all the measured things we all use every day to work together, they must match. You measure a window frame with a ruler or tape measure to make sure its dimensions are correct, so that when you install a pre-fabbed window, it fits correctly. The manufacturer of the window at some point used calibrated instruments to make it the right size. And your tape measure or ruler were at some point compared to the same internationally accepted units to make sure they measure accurately – to make sure they matched the window.
This is what calibration really is. It is making everyone’s measurements match. The accuracy of all instruments drift over time. In electronic instruments, components that make the measurements right gradually change. That means the readings made by that meter gradually wander away from their match with internationally accepted values, so it needs to be periodically checked and adjusted to make the measurement right again.