Introduction to the main indicators, display digits, and display characteristics of a digital multimeter
The display digits of a digital multimeter are usually 3 1/2 to 8 1/2 digits. There are two principles for determining the display digits of a digital instrument: firstly, the digits that can display all digits from 0 to 9 are integer digits; The second is that the numerical value of the fractional digit is based on the highest digit in the maximum displayed value as the numerator, and when measuring at full scale, the value is 2000. This indicates that the instrument has 3 integer digits, while the numerator of the decimal digit is 1 and the denominator is 2, so it is called 3 1/2 digits, pronounced as "three and a half digits". Its highest digit can only display 0 or 1 (0 is usually not displayed). The highest digit of a 32/3 digit (pronounced as "three and two-thirds digits") digital multimeter can only display numbers ranging from 0 to 2, so the maximum display value is ± 2999. In the same situation, it is 50% higher than the limit of a 3 1/2 digit digital multimeter, especially valuable for measuring 380V AC voltage.
Popular digital multimeter generally belongs to handheld multimeter with 3 1/2 digit display, while 4 1/2 and 5 1/2 digit (below 6 digits) digital multimeter can be divided into handheld and desktop types. Most of the 6 1/2 digits or above belong to desktop digital multimeters.
The digital multimeter adopts advanced digital display technology, with clear and intuitive display and accurate reading. It not only ensures the objectivity of readings, but also conforms to people's reading habits, and can shorten the reading or recording time. These advantages are not possessed by traditional analog (i.e. pointer) multimeters.
The Principle and Standards of Multimeter on/off Range
On/off range is a measurement mode that almost all multimeters have, used to measure the continuity (short circuit) of a circuit. Generally, it will be combined with a buzzer and an LED light. The buzzer will sound or the LED light will light up, indicating that the circuit is conductive. As shown in the figure, the symbol in the red box represents the on/off range of the multimeter.
On/off gear principle
When the multimeter is set to the on/off position, the internal circuit that is connected is: the black lead is connected to the negative pole of the internal battery, the positive pole of the battery is connected to a resistance with a small resistance value, and the other end of the resistance is connected to a red lead. The internal beeping circuit obtains a trigger signal from the resistor. If the two probes are short circuited or the resistance between them is small, then the voltage on the triggering resistor in the meter is higher, triggering a beep. If the resistance between two probes is large, then the partial voltage of the internal triggering resistor in series is small and cannot trigger the beep.
On/off gear standard
The general definition is that 80 ohms or less is continuity, otherwise it is non continuity. That is to say, connect the red and black probes of the multimeter on both sides of a circuit. If the resistance value of this circuit is less than 80 ohms, the multimeter will make a sound and believe that this circuit is conductive.
