Multimeters are electronic measuring instruments that combine several measurement functions in one unit. Multimeters can be hand-held devices useful for finding and correction of basic faults and field service work or bench instruments which can measure to a very high degree of accuracy. They can be used to troubleshoot electrical problems in a wide array of industrial and household devices such as electronic equipment, motor controls, domestic appliances, power supplies, and wiring systems. Analog multimeters are usually based on a microammeter whose pointer moves over a scale calibration for all the different measurements that can be made. However, most electricians use digital multimeters (DMM). DMMs have a digital or liquid crystal display (LCD), where measurement readings appear in exact numerical values. The display also alerts you to any pertinent symbols and warnings. The dial of digital Multimeters allows you to select the function you want to measure. The dial also plays another essential role in making any kind of electricity-related measurements: determining the range of measurement. The range that is selected on the dial determines the placement of the decimal point as it appears on the LCD. In turn, the position of the decimal point determines how refined, or precise, the reading is. This is called resolution. Digital multimeters also have auto-polarity for direct-current readings to show if the applied voltage is positive or negative. They also have the sample-and-hold feature which latches the most recent reading for examination after the instrument is removed from the circuit under test. Digital Multimeters also allow for a graphic representation, such as bar graph, of the quantity under test. They also have simple data acquisition features which help in recording maximum and minimum readings over a given period, in taking take a number of samples at fixed intervals. Digital pocket multimeters are used in a variety of measurement applications, including heating, ventilating and air conditioning (HVAC), building inspection, electronics, industrial and manufacturing, automotive and food service equipment. An electrical multimeter is used for electrical troubleshooting and testing in residential or commercial setups. It has low input impedance which prevents false reading caused by ghost voltage. An electrical multimeter also has automatic ac/dc voltage selection. HVAC multimeter is a compact true-RMS meter for HVAC troubleshooting. Among other multimeter features, it has a built-in thermometer for temperature measurement. An HVAC Multimeters also allows for microamps measurement to test flame sensors. It also has back-lighting options to ease the working in poorly-lit areas.