Electrical testing encompasses a broad range of methods for testing electronic components and troubleshooting and maintaining industrial, commercial, or residential electric systems. Electrical test equipment includes devices to measure voltage, AC current, capacitance, and resistance. Devices for electrical testing are commonly used by technicians working in industrial environments to inspect and maintain systems or by those installing electrical systems such as cabling, wiring, or HVAC (heating, ventilation, and air conditioning) in residential or commercial settings. Electrical testing tools can test equipment, wiring, and power supplies for electric faults that may pose a safety risk to people or damage to equipment. Some tools are used to verify the operation of electronic components in research and development or manufacturing environments.