Class of accuracy in electrical measurements and voltmeters have a high but not infinite internal impedance. Thus the measured parameters are somewhat altered during the measurements. Let E be the EMF of the source R be the resistance of the load and r be the resistance of the ammeter. The current through the load is I When the ammeter is connected in series with the load the current I is The difference introduced by the measuring device is then, The ratio of the difference to the actual value is Class of accuracy in electrical measurements In electrical engineering class of accuracy is a figure which represents
Electrical room enclosures of electrical equipment to prevent stray voltage and danger of electric shock, even during faults in the electrical system. Lightning protection requires different measures than protection from power-frequency faults. Electrical rooms may have electromagnetic shielding to prevent interference to nearby sensitive audio or video equipment. In large facilities access control systems may control admission to the room. Layout details and construction of electrical rooms will be controlled by local building code and electrical code regulations. Requirements for an electrical room relate to fire safety and electrical hazards. An electrical room is usually required to be secured from access by