A digital multi-function meter is a meter that displays the measured value digitally. An instrument that converts measurements into digital quantities and displays them in digital form. In industrial measurement, the measured variables or analog quantities such as displacement, current, voltage, and air pressure are converted into digital quantities through an analog-to-digital converter (referred to as analog-to-digital conversion). The digital multi-function meter displays the measured value in digital form, and the reading is intuitive. Generally include: use the dial and pointer to indicate the power, use the electromagnetic force-based electrical measurement circuit, analog-to-digital conversion and digital display.
1. The principle of digital multi-function meter
The principle of digital multi-function meters is relatively complicated. Various models and functions are different, and the principles are also different. The common thing is that they are all composed of electronic components, and they all convert the measured analog quantity into digital quantity (A/D conversion) , and finally the measured value is directly displayed by the display. Due to the advantages of intuitive reading, convenience, and no visual error, etc., it has developed rapidly. In recent years, it has been developed to be connected to other actuators (such as printers), and can also output switching or analog values to connect to control systems or computers. Some digital electrical instruments have their own central processing unit (CPU) and various memories, so some digital electrical instruments have been "microcomputerized" and intelligent.
2. Features of digital multi-function meters
2.1 Digital display, there is no visual error in the reading.
2.2 The accuracy is generally high. Since the digital electrical instrument has no movable parts of the electromechanical instrument, the influence of mechanical friction and deformation is very small. As long as the quality and performance of the components are no problem, the digital multi-function meter is relatively easy to manufacture. At present, it is not easy for general electromechanical instruments to achieve an accuracy of 0.1%, but digital multi-function meters can easily reach 0.05%. At present, some digital multi-function meters can achieve an accuracy of 0.01%.
2.3 High sensitivity. Since some digital multi-function meters are equipped with various amplification circuits or devices, they can measure smaller signals, such as voltage signals of about 1mv, current signals of about 1mA, and frequency signals of 0.01Hz.
2.4 High input impedance. Digital multi-function meters generally have their own working power supply. Except for the measurement current, the general impedance can be made higher, so that the impact on the measured physical quantity is very small during measurement.
2.5 Easy to use. Especially the portable and desktop instruments used in the laboratory can be made into multi-range (currently there are KM meters with a display range of -1999~9999), multi-functional instruments (can measure current, voltage, frequency, power, line speed and speed).
2.6 The anti-interference performance is poor. Due to the high sensitivity of the digital multi-function meter, its side effect is that the anti-interference performance is poor, and changes in the external magnetic field and electric field may easily cause changes in readings.
2.7 The accuracy of digital multi-function meters is expressed differently from pointer meters. Digital multi-function meters generally use the upper limit or reading value as a percentage of the reference value plus a few numbers to indicate the accuracy of the meter, such as KM Series of digital display instruments, system accuracy 0.1% (DC), 0.2% (AC) full scale 1 word. Generally, multi-function and multi-range digital multimeters have different functions and ranges, and the accuracy is also different. Therefore, you should pay attention when choosing and using digital multi-function meters. It is best to find a specialized instrument company to select the type for you.