Ammeter through a wire which expands as it heats. Although these instruments have slow response time and low accuracy, they were sometimes used in measuring radio-frequency current. These also measure true RMS for an applied AC. In much the same way as the analogue ammeter formed the basis for a wide variety of derived meters, including voltmeters, the basic mechanism for a digital meter is a digital voltmeter mechanism, and other types of meter are built around this. Digital ammeter designs use a shunt resistor to produce a calibrated voltage proportional to the current flowing. This voltage is then measured by
Electrical contractor classified by three major types of work performed. Electrical contractors employ workers in many capacities, determined by their level of training and experience. Some common jobs include: In the United Kingdom, the two main trade associations are the Electrical Contractors' Association, covering England, Northern Ireland and Wales, and SELECT - the Electrical Contractors' Association for Scotland. The main certification bodies are the National Inspection Council for Electrical Installation Contracting and Elecsa. The National Electrical Contractors Association (NECA) is the largest trade association in the electrical contracting industry, with about 4500 members. NECA publishes an industry magazine, and sponsors an annual