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Digital Voltmeter Solution
In the process of measuring electricity, the content includes current, voltage and frequency, among which the factor with the highest measurement frequency is voltage. With the advancement of science and technology, measuring high-precision voltage has become a common measurement difficulty faced by all walks of life. Digital voltmeters that replace pointer surfaces with digital surfaces and display measured values on LCD panels or digital tubes have important promotion. value.
Basic Specifications of Digital Voltmeters
Voltage measurement range: 0V-100V
Current measurement range: 0-999mA; 0-10A; 0-50A; 0-100A
Power supply range: 3V-30V
Voltage error: +-0.1%
Current error: +-1%
1. Overview of digital voltmeter
Digital voltmeter refers to a voltmeter that uses digital measurement technology to convert continuous analog quantities into discrete digital forms and display them. With the progress of society, the pointer voltmeter has been used with high frequency for a long period of time in the past, and its shortcomings such as inconvenient reading, low precision and relatively single function have gradually emerged, which can no longer meet the needs of today's society. Digital voltage The appearance of the table effectively solves the above problems. The digital voltmeter made by single-chip microcomputer not only has the characteristics of high accuracy, strong expansion ability, high integration and strong anti-interference ability, but also can communicate with the computer in real time, which coincides with the direction of social development. combine. At this stage, the digital voltmeter has been recognized by many fields such as automatic test system, electronic and electrical measurement, and has achieved good results in the application process.
2.The classification of digital voltmeters
There are many types of digital voltmeters, and there are many basis for their classification. The common classification methods include the following: ① Divide digital voltmeters into low-speed and high-speed according to the measurement speed; ② Divide according to the number of digits. The digital voltmeter is divided into 3/2 digits, 5 digits and 8 digits; ③ According to the quality and volume, the digital voltmeters are divided into desktop, portable and pocket.
Generally speaking, the division of digital voltmeters is mainly based on the A/D conversion method. According to the A/D conversion method, digital voltmeters can be divided into two types: indirect conversion and direct conversion. Among them, indirect conversion is divided into voltage-frequency transformation and voltage-time transformation. Voltage-frequency conversion refers to converting the measured voltage to a frequency value during the measurement process, and then displaying the frequency value through the frequency meter, and at the same time, it can also respond to the voltage value. Voltage-time conversion refers to the conversion of the measured voltage to the time interval during the measurement process. The larger the voltage, the larger the time interval, and then control and count the timing pulse according to the size of the time interval. The counted value represents the is the voltage value.
At the same time, there is also a comparative voltmeter, which is a digital voltmeter that compares the measured voltage with the reference voltage in a decreasing state to obtain the measured voltage value, and displays the value through the display. It takes a long time to compare one by one, and often requires several beats to complete. If you want to complete a measurement in a very short time, you need to speed up the beat speed.
3. Performance and characteristics of digital voltmeter
3.1 Compared with the accuracy
Compared with analog voltmeters, one of the outstanding advantages of digital voltmeters is higher accuracy. For example, for 31/2 digits and 41/2 digits, the accuracy of digital voltmeters is as high as ±0.1% and ±0.02 %.
3.2 Strong scalability
Based on the digital voltmeter, according to actual needs, it can be expanded into different types of intelligent instruments, general-purpose digital instruments, digital multi-meters, special-purpose digital instruments, etc. If the measurement of AC and DC current and voltage is completed through the conversion circuit, the calculation of power, effective value, peak value and other values can be realized through characteristic calculation. In addition, factors such as phase, period, frequency, etc. can also be measured via change adaptation. 3.3 High input impedance Through investigation, it can be found that for most digital voltmeters, 10~10000MΩ is a common input impedance. Of course, the highest value of input impedance can reach 1TΩ. During the measurement process, only a very small current is drawn in the circuit under test. The advantage of this is that the working state of the signal source under test will not be unnecessarily affected, thereby reducing the internal resistance of the signal source to a large extent and causing the measurement to occur. chance of error. 3.4 Higher resolution The resolution of a digital voltmeter refers to (except zero) the percentage of the minimum and maximum values that the digital voltmeter can display. For digital voltmeters, the 1 word at the end of the lowest voltage range can represent a voltage value that can respond to the sensitivity of the meter. In addition, as the number of displayed digits gradually increases, the last word will also have improved.
3.3 The display is intuitive and clear
Compared with the pointer voltmeter, the advantage of the digital voltmeter is that it can avoid inspection or other man-made measurement errors, so that the reading can maintain the corresponding accuracy and objectivity. In addition, the digital voltmeter is more in line with people's reading habits in daily life, which can greatly shorten the time required for reading and recording. Of course, the identifier display is also another excellent performance of the digital voltmeter. With this performance, people can directly read special symbols, unit symbols, and measurement bullets.
3.4 Strong anti-interference ability
Most of the digital voltmeters below 51/2 digits use integral A/D converters. The serial mode rejection ratio and common mode rejection ratio of the converter are 100dB and 80~120dB respectively. In addition, some high-end digital voltmeters also apply advanced science and technology represented by floating protection and digital filtering, which effectively improves the anti-interference ability.
3.5 Higher level of integration
Most of the digital voltmeters used at this stage use CMOS integrated circuits. Compared with pointer voltmeters, they have high integration and extremely low power consumption.
3.6 Fast measurement rate
First of all, you need to understand the meaning of the measurement rate. The measurement rate refers to the number of tests completed by the digital voltmeter for the measured voltage in seconds, and the unit is times/s. The factor that can directly affect the measurement rate is mainly the conversion rate corresponding to the A/D converter, and the reciprocal of the conversion rate is the measurement period. The measurement rates of 31/2-digit and 51/2-digit digital voltmeters are several times/s and dozens of times/s respectively. The 81/2-digit digital voltmeter has greatly improved the measurement rate by reducing the bit, and the measurement rate of the digital voltmeter is as high as 100,000 times/s.
Through the analysis of the content described above, it can be found that the appearance of digital voltmeter is the inevitable result of social development. The digital voltmeter not only made up for the deficiencies of the pointer voltmeter in terms of accuracy and integration, but also combined with the computer. The article mainly expounds the performance and characteristics of the digital voltmeter from the aspects of measurement rate, anti-interference ability, resolution and expansion ability. With the development of technology, the digital voltmeter will inevitably show better performance.
Shenzhen Zuchuang Microelectronics Co., Ltd. has solutions for digital display voltmeters, has participated in the circuit design and program development of many current and voltmeters, and can provide product control chips such as AC voltmeters and DC voltmeters. If you have digital display voltmeter, digital voltmeter, current voltmeter, AC voltmeter, DC voltmeter, vehicle voltmeter, automobile voltmeter, high voltage voltmeter, LED/LCD voltmeter, three-phase current voltmeter, digital voltage You can rest assured to entrust us with the solution development needs of voltage measurement tools such as meter heads, digital display AC voltmeters, digital DC voltmeters, digital current voltmeters, and automotive voltmeters. We have rich experience in customizing and developing electronic products, and can quickly Evaluate development cycle and material price.
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