What kind of multimeter do I need for automotive?
Automotive multimeters are also called multimeters. The two mainstream multimeters in the market today are pointer multimeter and digital multimeters. Multimeter has complete measuring functions, simple operation and convenient carrying, and has become one of the most widely used electrical and electronic measuring instruments. It is also indispensable in other industries, such as electrical maintenance, communication equipment maintenance and automobile maintenance, especially electrician, electronic beginners and radio enthusiasts. Mastering the use methods and skills of multimeter is the basis for quickly judging the quality of components and detecting whether the circuit (or circuit) of electrical equipment is normal. Nowadays, digital measuring instruments have become the mainstream and tend to replace analog instruments. Compared with analog instruments, digital instruments have high sensitivity, high accuracy, clear display, strong overload capacity, easy to carry and simple to use.
Digital multimeter completes the measurement according to the conversion between analog and digital quantities, and it can display the measurement results digitally. The error of digital multimeter in measuring resistance is smaller than that of analog multimeter, but the relative error is still relatively large when it is used to measure resistance with small resistance. There are many types of digital multimeter, but the panel layout is basically the same, including display screen, power switch, function range selection switch and stylus jack (the role of jack may be different with different models).
Characteristics and safety information of digital multimeter
(1) adopting digital measurement technology
Digital multimeter adopts digital measurement technology, converts the measured analog quantity into digital quantity through A-D converter, and finally outputs it as digital quantity. As long as the meter does not jump, the measurement result is unique, which not only ensures the objectivity and accuracy of reading, but also conforms to people's reading habits. The display result is clear at a glance, and it will not appear artificial measurement error like analog multimeter.
(2) liquid crystal display
Early digital multimeters mostly used liquid crystal display (LCD) with a word height of 12.5 mm. At present, in order to improve the display clarity, most digital multimeters use large-size LCD with a word height of 18mm, and DT940C, DT960T, DT970, DT980 and DT9205 use super-large LCD with a word height of 25 mm.. Most of the new digital multimeters have added function identifiers, such as unit symbols mV, V, kV, μA, mA, A, ω, kω, mω, nS, kHz, pF, nF, μF, and measurement items symbols AC, DC, LOω, LO BAT (low voltage symbol), H (reading hold symbol) and AUTO (automatic range symbol).
(3) Wide measuring range
At present, the measuring range of new digital multimeter is wider than that of analog multimeter, such as the measuring range of resistance (Ω) is 0.01~20MΩ (or 200mΩ); The measuring range of DC voltage range (DCV) is 0.2 ~ 1000 V; The measuring range of AC voltage range (ACV) is 0.01~700V (or 750 V); The measuring range of frequency band (F) is 10Hz ~20kHz (or 200kHz).
(4) high accuracy
The accuracy (precision) of digital multimeter is much higher than that of analog multimeter. Because the accuracy of digital multimeter is the synthesis of systematic error and random error in the measurement result, it indicates the consistency between the measurement result and the true value (standard value) and can reflect the measurement error. In general, the higher the accuracy, the smaller the measurement error.
(6) High resolution
Resolution is the ability of digital multimeter to distinguish the measured small change. It reflects the sensitivity of the instrument, and the resolution of the instrument is different in different ranges. The resolution of the instrument in the range is defined as the resolution index of the digital multimeter.
Sometimes, the resolution is also called the sensitivity of the instrument. The resolution of digital instruments increases with the increase of display digits.
Resolution index can also be expressed by resolution. Resolution refers to the percentage of decimal digits that can be displayed by the instrument. For example, DT8900 31/2 digit digital multimeter can display decimal digits as 1 and digit as 1999, so the resolution is equal to 1/1999 ≈ 0.05%.
It should be pointed out that resolution is different from resolution;
For example, the resolution of 31/2-bit and 33/4-bit instruments is the same, both of which are 100μV, but they are different.
Resolution and accuracy belong to two different concepts. Resolution represents the "recognition" ability of the instrument for small signals, that is, the "sensitivity", while accuracy reflects the "accuracy" of the measurement, that is, the consistency between the measurement results and the true values. The two are not necessarily related and cannot be confused. In fact, the resolution is only related to the number of digits displayed in the instrument, while the accuracy is related to the comprehensive error and quantization error of the A/D converter and function converter inside the instrument. In practical application, the higher the accuracy and sensitivity, the better, but also depends on the specific object to be measured, otherwise it is also a waste.
