What are the technical parameters and measurement methods of a digital multimeter
1. Resolution, Word Count, and Bits
Resolution refers to the ability of a multimeter to distinguish small signals during measurement. Knowing the resolution of a multimeter can determine whether it can observe small changes in the measured signal. For example, if a digital multimeter has a resolution of 1mV on a 4V range, it indicates that it can observe a change of 1mV (1/1000 V) when reading 1V.
If you must measure a minimum length of 1/4 inch (or 1 millimeter), you will not purchase a ruler with a minimum scale of 1 inch (or 1 centimeter). If the normal temperature is 98.6 degrees Fahrenheit, a thermometer that can only measure whole degrees is not very useful. You need a thermometer with a resolution of 0.1 degrees.
The words' bit 'and' word 'are used to describe the resolution of a multimeter. They can be grouped by the number of words or digits displayed on a digital multimeter.
One piece of 3 ½ The digital multimeter can display three whole digits (0 to 9) and one "half digit" (only one "1" is displayed or left blank). One piece of 3 ½ The display resolution of the digital multimeter is high, which is 1999 words. One piece of 4 ½ The display resolution of the digital multimeter is as high as 19999 words. Compared to "bit", using "character" can more accurately describe the accuracy of a multimeter. Current 3 ½ The resolution of a digital multimeter may be as high as 3200, 4000, or 6000 words.
For certain measurements, a 3200 word multimeter can provide better resolution. For example, if you want to measure a voltage of 200V or higher, a 1999 word multimeter cannot measure 0.1V. A 32 million meter can display up to 0.1V when measuring voltages up to 320V. Before exceeding a voltage of 320V, this resolution is the same as that of the more expensive 20000 word multimeter.
2. Accuracy
Accuracy is the maximum allowable error generated under specific operating conditions. In other words, accuracy represents the closeness between the measured value displayed on a digital multimeter and the actual value of the measured signal.
The accuracy of a digital multimeter is usually expressed as a percentage of the reading. An accuracy of 1% of the reading indicates that if the displayed reading is 100V, the actual voltage value may be any value between 99V and 101V.
The technical parameters may also include a range of bits added to the basic accuracy parameter. This range represents the number of words that may vary in the rightmost digit of the displayed value. In this way, the accuracy in the above example can be expressed as "± (1%+2)". Therefore, if the displayed reading is 100V, the actual voltage value will be between 98.8V and 101.2V.
The parameters of an analog multimeter are determined by the full-scale error, rather than the percentage of the displayed reading. The typical accuracy of an analog multimeter is ± 2% or ± 3% of full scale. At 1/10 full scale, the accuracy becomes 20% or 30% of the reading. The typical basic accuracy of a digital multimeter is based on readings between ± (0.7%+1) and ± (0.1%+1) or better.
3. Ohm's law
The voltage, current, and resistance of any circuit can be calculated using Ohm's law, which is expressed as "voltage equals the product of current and resistance" (see Figure 1). Therefore, if any two values in the formula are known, the third value can be determined.
A digital multimeter utilizes Ohm's law to directly measure and display resistance, current, or voltage. The following describes how to use a digital multimeter to conveniently measure the required parameters.
4. Digital and analog displays
The digital display has high accuracy and resolution, and can display three or more digits for each measurement value.
The accuracy of analog pointer display is not very high, and the effective resolution is also low, because it is necessary to estimate the value between two tick marks.
Bar charts can display signal changes and trends like analog pointers, but they are more durable and less prone to damage compared to pointers.
