The principle and function of the electric meter field calibrator
With the gradual improvement of the power grid construction, the corresponding power distribution devices have developed rapidly, the accuracy level of the power meters has become higher and higher, and the requirements for the power meter on-site calibrators have also increased. The instrument power indicator is generally required to reach level 0.05. There must be harmonic analysis, incorrect wiring judgment, vector graph display, and correction coefficient calculation on the function. In addition, the measured data requirements are saved and uploaded to the PC for management and application. It is also required to carry Convenient, small size, low power consumption, so using ARM and CP2102 technology will be able to meet the design requirements. Welding Components ,Steel Welded Assemblies ,Laser Welding Subassembly,Steel Welded Assembly Ningbo Metal Sharing Supply Chain Management Co., Ltd , https://www.sheetsharing.com
First, the hardware principle Hardware by the analog input channel, sample and hold circuit, A / D converter, CP2102 digital signal processor, ARM and its peripheral components. In the input channel, the three-phase voltage is directly connected and is sampled by a precision resistor to the A/D converter. The current sampling is divided into three ways: precision transformer, 5A clamp transformer and 500A clamp transformer to meet the different requirements of on-site calibration.
The collected signal is converted into a digital signal by 16-bit serial A/D conversion. The sample-and-hold device guarantees the synchronization of sampling, so that the voltage and current of each phase are sampled at the same time, and finally input to the digital signal processing CP2102 in a serial manner. CP2102 is the abbreviation of digital signal processor (Digital Signal Processor). It performs high-speed operation on the sampled signal, processes it, and transmits the result to the central processing unit (ARM) via the bus. The central processing unit (ARM) performs post-processing on the CP2102 processing results to implement functions such as man-machine conversation, data storage, and function switching. The monitor adopts 26k true color large screen with 640×480 resolution, and the background color can be adjusted to adapt to different environments.
Second, the realization of the function of the instrument design indicators for the 0.05 level, mainly by the sampling circuit and A / D to ensure that the algorithm also has a great influence. The instrument adopts non-synchronous sampling. The sampling frequency is not synchronized with the measured signal, which will bring additional errors. The residual error can be corrected by software method. After reference 3 has been tested, the basic power error can meet the design requirements. Due to the high performance of ARM, combined with various conditions of on-site verification of the energy meter, the instrument provides a wealth of extended functions, mainly in the following aspects.
1. The instrument can receive the information to be calibrated from the host computer, including the phase line, constant, type, transformer magnification, number, and transformer capacity. When the meter is calibrated, only the input number can be used to load all the information for verification. When the verification result is stored, the above information may also be included and there is a verification time, error, and electrical measurement information at the time of measurement. The peak-to-valley flatness information that can be calibrated can be obtained manually or via 485, including positive and negative active power and positive and negative reactive power. The number of storage 1000 blocks.
2. The large-screen LCD can display three-phase voltage, current, power, frequency, power factor, and display current gear (base meter, 5A clamp meter, 500A clamp meter) information in the verification interface. Can display two errors, if it is the main table sub-table shows the error of the two tables, if it is a multi-function energy meter can simultaneously display active and reactive error.
3. Can carry out the word test, can accumulate the electric energy, check the working condition of the energy meter character wheel.
4. Can display the phasor diagram and phase value, check the wiring function (error or correct wiring), directly calculate the correction factor under the wrong wiring conditions, can recover the lost power in time.
5. It can test angle difference, ratio difference and error of low voltage current transformer CT in measuring device.
6. Has a harmonic analysis function, display line distortion, various harmonic content, waveform, can also check the fundamental wave table.
7. It is the adoption of ARM technology that can make the power meter calibrator with powerful functions small in size, small in power consumption (important calibrator of the field calibrator), easy to carry, and it will surely become effective for electric energy measurement staff. equipment.