Measuring Bus Frequency During Transients: Some Fundamentals

The success of digital instruments seems sometimes to founder when it comes to frequency measurement. Measurement science has developed certain broad principles over the centuries. They are so deep-rooted they are sometimes overlooked. The paper defines measurement largely by elucidating some of these broad principles, and defines frequency, a word subject to much interpretation, as a mathematical entity. Methods of measuring frequency are discussed. An example of the behavior of frequency during a fault, measured in accordance with all the basic principles, is given. The results are not particularly useful. Methods of improving the usefulness are discussed, but may violate some of the basic principles. In essence, “frequency” may not be the best measurand for a signal obtained during a fault.