Inductance standards and decades provide highly accurate and digitally variable standard values of inductance for calibration, comparison and testing. Inductance opposes a change in an electrical circuit and is usually measured in henries (H). Inductance standards usually consist of a single, fixed value component or several components (e.g., several fixed value resistors) that are not in the same circuit. Continuously variable devices often include a potentiometer. Inductance standards with more than one component have multiple posts or a rotary switch for selecting different resistance values. Most inductance decades consist of several components in the same circuit. The standard resistance value is selected by varying the number of resistors in the series or parallel circuit. Transfer, primary, and laboratory grade inductance standards are used to compare or transfer accuracies from the National Institute of Standards and Technology (NIST) or other nationally certified organizations to working decades. Typically, these working devices are robust or rugged units for production or in-line testing and calibration.
