Six Standards for Selecting Digital Multimeters
(1) Reliability: Especially under harsh conditions, reliability is more important than ever before.
(2) Security: The primary consideration in the design of digital multimeters, especially after independent testing by certified laboratories and printing the logos of testing laboratories such as UL, CSA, VDE, etc.
(3) Resolution: Resolution, also known as sensitivity, is the smallest quantization unit of the measurement result of an exponential multimeter, which can show small changes in the measured signal. For example, if the resolution of a digital multimeter is 1mV within the 4V range, then when measuring a 1V signal, you can see a small change of 1mV. The resolution of a digital multimeter is generally expressed in digits or words.
The resolution of a digital multimeter is a very important indicator, just like when you want to measure a length less than 1 millimeter, you will definitely not use a ruler with * small units in centimeters; If the temperature is 98.6 ° F, it is not useful to measure with a thermometer with only integer markings. You need a thermometer with a resolution of 0.1 ° F.
A 3 and a half digit table can display three full digits from 0 to 9 in the last three digits, while the first digit only displays one and a half digits (showing 1 or not), meaning that a 3 and a half digit table can achieve a resolution of 1999 words; A four and a half digit digital multimeter can achieve a resolution of 19999 words. Using words to describe the resolution of a digital table is better than using digits to describe it. The resolution of the current 3 and a half digit multimeter has been increased to 3200 or 4000 words. The 3200 word digital multimeter provides better resolution for certain measurements. For example, a 1999 word meter cannot display 0.1V when measuring voltages greater than 200V. The 3200 word digital multimeter can still display 0.1V when measuring a voltage of 320 volts. When the measured voltage is higher than 320V and a resolution of 0.1V is required, a more expensive 20000 word digital multimeter should be used.
(4) Precision: refers to the maximum allowable error that occurs in a specific usage environment. In other words, accuracy is used to indicate the degree to which the measured value of a digital multimeter is close to the actual value of the measured signal. For a digital multimeter, accuracy is usually expressed as a percentage of the reading. For example, a reading accuracy of 1% means that when a digital multimeter displays 100.0V, the actual voltage may be between 99.0V and 101.0V. In the detailed instruction manual, there may be specific numerical values added to the basic accuracy, which means the number of words to be added when transforming the right end of the displayed *. In the previous example, the accuracy may be marked as ± (1%+2). Therefore, if the reading of the multimeter is 100.0V, the actual voltage will be between 98.8V and 101.2V. The accuracy of an analog meter (or pointer multimeter) is calculated based on the error of the full range, rather than the displayed reading. The typical accuracy of a pointer multimeter is ± 2% or ± 3% of the full range. The typical basic accuracy of a digital multimeter is between ± (0.7%+1) and ± (0.1%+1) of the reading, or even higher.
(5) Ohm's Law: Ohm's Law reveals the relationship between voltage, current, and resistance. By applying Ohm's law, any circuit voltage, current, or resistance can be calculated as follows: voltage=current x resistance. Therefore, as long as you know any two values in the formula, you can calculate the third value. A digital multimeter is the application of Ohm's law to measure and display resistance, current, or voltage.
(6) Digital and analog pointer display: In terms of accuracy and resolution, digital display has great advantages, and measured values can be displayed in three or more digits. Analog pointers are slightly inferior in accuracy and resolution, and we generally rely on estimating the position of the pointer to read. The digital multimeter has a bar like analog pointer that displays signal changes and trends, but it is more durable and reduces damage
