Multimeters are divided into analog multimeter and digital multimeters according to the structure of meter and method of measurement.Multimeters are a kind of electric parameter measuring instrument, and also tools that are applicable to all electric occasions.In comparison with analog multimeters, digital multimeters have the merits of higher measurement accuracy, higher input impedance, and direct reading, etc.Digital multimeters can be divided into two categories according to its appearance: handheld multimeters and desktop multimeters.
Compared to handheld multimeters, desktop multimeters are generally advantageous due to having more digits and more measuring functions and being more accurate. But desktop multimeters are more expensive, bulkier and not convenient to carry around, thus being applied mostly to production test, scientific research, and development and teaching, etc. Though handheld multimeters are inferior to the desktop ones in terms of accuracy and function, yet they are cheaper and easier to carry around; they are more applicable to households and being carried around for maintenance.
On the basis of range selection, multimeters can be further divided into two categories: auto range multimeters and manual range multimeters.Auto range multimeters and manual ones make no big difference in accuracy and function, just like the auto and manual gear cars of the same type. The major difference in the two kinds of multimeters lies in the process of range selection.The multimeter is designed with multiple measuring ranges.According to the requirements of measurement accuracy, there are three and a half digit, four and a half digit and five and a half digit multimeters. The more the digits there are, the more accurate the multimeter will be.Basic measurement parameters of multimeters are direct voltage, alternating voltage, direct current, alternating current, resistance, and capacitance, etc.
The grading of multimeters will be determined in line with the needs and the function of main IC. For instance, a multimeter that is able to measure 200V direct voltage to the utmost might have the voltage range designed as 200mV, 2V, 20V, and 200V. If a user wants to test 19.5V voltage, he/she must choose the 20V measuring range to get the most accurate reading. If 200V is selected, the given reading will be inaccurate. If 2V is chosen by accident, it will exceed the limiting value of the measuring range, the meter will display over range indication (OL). Therefore, manual range multimeters require users to try out measuring ranges from the maximum to the minimum one to test unknown parameters; users will need to change over from one range to another time after time, or to estimate the scope of the parameters to be measured in advance, and to select a range accordingly; it is prone to misoperation in this process. However, the auto range multimeters will spare users the trouble of range selection. After an electrical parameter is an input into the instrument, the chip of the instrument will figure out the range of the parameter and choose a correct measuring range. It will be more convenient and safer. But it will take the chip some time to read, analyze and judge the measuring range, it will respond to the electrical parameter and display a reading at a slower speed than the manual range multimeter. For some extremely experienced electricians who only need to test relatively simple parameters, they may give a quick valuation on the electrical parameter to be measured, and select a range accurately; the manual range multimeters will be more advantageous in quick response and lower price, compared to auto range multimeters at the same level. However, as for common users, the convenience and safety of auto range multimeters are unparalleled. As the chip of auto range multimeters keeps upgrading, the price advantage of manual range multimeters is shrinking step by step. We can believe that the auto range multimeters will gradually dominate the market.