I. Core hardware precision control system
High-precision Sampling Circuit Design
Current Sampling: Manganese-copper shunt (accuracy ±0.1%) or low-bias Hall sensor (linearity ≤0.05%), together with 24-bit ADC (e.g., ADS1256), the sampling rate is up to 20kHz, which ensures that the current waveform is not distorted.
Voltage sampling: 0.01% accuracy metal foil resistor (temperature coefficient <5ppm/°C), parallel compensation capacitor (error ±0.5%) to eliminate phase shift, voltage measurement error is controlled within ±0.2%.
Optimization of metering chip and algorithm
adopts special metering chip (e.g. ATT7053E) with built-in power metering kernel (active precision 0.2S level), together with FFT algorithm to analyze harmonic components in real time, and the metering error of the 2nd-31st harmonics is ≤±0.5%.
Temperature compensation mechanism: the chip has a built-in temperature sensor (accuracy ±0.5℃), and through the segmented linear compensation algorithm, the accuracy drift within the range of -20℃~+60℃ is controlled within ±0.3%.
Anti-interference hardware design
EMI filter network (common mode inductor + X/Y capacitor) is installed on the power supply side to suppress grid interference; PCB layout adopts a 4-layer board structure to isolate the power supply layer from the ground layer, and the impedance of the signal alignment is controlled at 50±5Ω.
Critical signal paths (e.g., sampling circuits) are encapsulated in shielded enclosures, and the electrostatic protection reaches IEC 61000-4-2 Level 4 (±15kV air discharge). The key signal paths (such as sampling circuits) are encapsulated in shielded enclosures.
Manufacturing process and calibration technology
Fully automated calibration process
Multi-point calibration by four-quadrant power calibration device (accuracy 0.05 level) before delivery:
Low load point (1% Ib): error ≤ ± 0.5%;
Common load point (50% Ib): error ≤ ± 0.2%;
Overload point (120% Ib): error ≤ ± 0.3%.
Adopt laser trimming technology (resolution 0.1μΩ) to dynamically compensate the sampling resistance to ensure the consistency of full-range accuracy.
Temperature cycling aging test
The finished product has gone through - 25℃~+70℃ (humidity 95% RH) 300 times of cycling aging, keeping 4 hours for each cycle, and re-calibrating after aging to ensure that the temperature drift is ≤±0.2%/10℃ in long-term operation.
Environmental adaptability solutions
| environmental factors | Influence mechanism | Response |
| Temperature fluctuations | Temperature drift of sampling elements and changes in chip performance | Adopt a component with a temperature drift of <10ppm/°C, and a built-in dynamic temperature compensation algorithm |
| Electromagnetic interference | Sampling signal distortion and misjudgment of metering chip | The shell is made of galvanized steel sheet (shielding efficiency ≥ 60dB), and the inside is magnetically shielded |
| Mechanical vibration | Loose component solder joints and offset sampling circuits | The key components are fixed with underfill glue (Tg≥125°C), and the PCB is designed with stiffeners |
| Grid harmonics | The fundamental measurement error increases | IIR digital filter (cut-off frequency 2kHz) is used to suppress higher harmonic interference |
Software algorithm and data protection
Dynamic error correction technology
Real-time monitoring of voltage and current phase difference, automatically start phase compensation algorithm when the power factor is <0.5, reactive power metering error ≤±1.0%.
Abnormal data identification: Kalman filtering algorithm to filter pulse jitter (jitter time <50ms), to ensure that the pulse counting accuracy of 100%.
Data security and traceability
measurement data using CRC-32 calibration + AES-128 encryption storage, to prevent tampering; every 15 minutes to generate frozen data, can be traced back to the measurement curve within 3 months.
Communication interface (RS485 / Bluetooth) using hardware flow control, data transmission BER <10-⁶, to ensure that the accuracy of remote meter reading is consistent with the local.
Five, installation and maintenance guarantee
standardized installation scheme
guide rail installation torque control at 2.5-3.0N・m, to ensure that the contact resistance <50mΩ; into the end of the line using anti-loosening terminals (such as WAGO cage spring terminal), to avoid poor contact caused by the measurement error.
Installation spacing requirements: the distance between neighboring meters ≥20mm, ensure good heat dissipation, ambient temperature deviation ≤±5℃.
Intelligent Operation and Maintenance System
supporting management platform for real-time monitoring of the meter status:
measurement error exceeds the limit (such as > ± 0.5%) automatic alarms;
battery voltage is lower than 2.8V triggered by replenishment reminder;
to provide remote on-line calibration function (subject to authorization by the metrology department).
Industry standards and certification system
complies with GB/T 17215.321-2008 "0.2S Class Static AC Active Energy Meter" standard, and has passed the type test of power meter of the national grid (error test, environmental adaptability test and other 32 indexes).
It has obtained the calibration certificate issued by CNAS accredited laboratory, and the full-range error curve meets the requirements of 0.2S level (error ≤±0.2%), and the precision decay is ≤0.1% after 1000 hours of continuous operation.
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