Architectures (1-phase/3-phase SoCs, AFE+MCU, PQ/harmonics, sub-metering), current/voltage sensors (shunt/CT/Rogowski/Hall/fluxgate), measurements & accuracy, communications and security, power & hold-up, key specs, design hooks, applications, and quick cheats.
Architectures
Single-Phase Metering SoC
On-chip ΣΔ/SAR ADC + DSP for P/Q/S, kWh/kvarh, RMS, PF and line frequency; smart plugs and household meters.
Three-Phase Metering SoC
Synchronous sampling with phase compensation, phase-loss/sequence detection for industrial/utility meters.
Metrology AFE + MCU
Discrete metrology AFE plus comms/application MCU for protocol/security customization.
Harmonics / Power-Quality AFE
THD and 2–40th harmonics with transient/flicker event analysis for PQ monitoring.
Sub-Meter / Branch Monitoring ICs
Many current channels with a shared voltage input for panels, cabinets and buildings.
Current / Voltage Sensors
Shunt Resistor
High precision/low phase shift; needs isolation (iso-ADC/isolators). Power loss P=I²R.
Current Transformer (CT)
Inherently isolated, low loss; watch core saturation and choose proper burden resistor.
Rogowski Coil
Wideband, non-saturating (output ∝ di/dt); needs accurate integrator for large/dynamic currents.
Hall / Fluxgate
Measures DC/low-frequency with isolation; higher BOM cost but versatile.
Voltage Divider / PT
Precision dividers or PTs; watch thermal drift and safety distances.
Measurements
Active/Reactive/Apparent Power & Energy
kWh/kvarh accumulation with forward/reverse energy support.
Power Factor & Phase Angle
Maintain accuracy at low PF via phase compensation and low-noise front ends.
RMS & Line Frequency
Auto detect 50/60 Hz and compute RMS V/I robustly.
Harmonics / THD
THD and harmonic power decomposition for PQ analytics.
Events & Anti-Tamper
Neutral-loss/reverse wiring, magnetic attack and N-L-PE imbalance detection.
Accuracy & Standards
Accuracy Class
Class 0.2S / 0.5S / 1.0 under IEC 62053 series and ANSI C12.20.
Dynamic Range
2000:1–10000:1; maintain error at low currents (e.g., 10 mA).
Temp Drift & Long-Term Stability
Temperature compensation of meter constants across life.
Safety / Isolation
Over-voltage categories, creepage/clearance and UL/IEC 62368/61010 compliance.
Comms & System
Energy Pulse (CF/KY)
Calibration/time-sync pulses; interface to optos/MCUs.
Digital Interfaces (UART/I²C/SPI)
Reading/configuration and firmware updates.
Field/Backhaul Comms
RS-485/MBus/PLC/Ethernet/Cellular/LoRa with DLMS/COSEM/Modbus and local IR.
TOU / RTC
Multiple tariffs (peak/valley) with retained RTC over power-fail.
Relay / Contactor Control
Load cut-off and state sensing.
Security & Protection
Secure Storage / Anti-Rollback
Monotonic energy/counters in FRAM/EEPROM/secure regions.
Crypto & Secure Boot
AES/CMAC, key injection and signed firmware.
Event & Tamper Log
Timestamps with reason codes; black-box retention on outages.
Front-End Protection
TVS/RC/fuse/GDT design for surge/lightning levels.
Power & Hold-Up
Wide-VIN Meter PSU
Isolated AC/DC with good efficiency and controlled start-up inrush.
Power-Fail Detect & Safe Commit
Supercap/hold-up to guarantee monotonic writes during power-down.
Ultra-Low-Power RTC / AMR
Battery-powered endpoints with wake-on-event metering.
Key Specs
ADC
Resolution (16–24-bit), ≥2–8 kS/s per channel, SINAD/ENOB and channel synchronicity.
Phase & Gain Errors
Phase compensation steps; consistency across temp and current range.
Harmonics & PQ
THD, harmonic order support and windowing (e.g., 10/12 cycles for 50/60 Hz).
Anti-Tamper Capability
Detect missing neutral, reverse flow, external magnet and bypass paths.
NVM
Endurance (write cycles), atomic commits on power-fail and long retention.
Interfaces & Protocols
DLMS/COSEM stacks and compatibility with head-end/concentrators.
Safety & Immunity
Creepage/insulation and ESD/surge to IEC 61000-4-2/-4-5.
Design Hooks & Pitfalls
Shunt Heating & Drift
Low-TCR (≤50–100 ppm/°C) 4-terminal shunts; calibrate across temp/current.
CT Saturation
Select burden/core to avoid distortion under harmonics/surges.
Rogowski Integrator
Accurate RC integrator with phase correction and zero-drift control.
Phase Compensation
Voltage/current path delay mismatch → PF error; use on-chip correction plus field calibration.
AFE Layout
Kelvin connections, short loops and A/D ground partition; isolate mains crosstalk & HF noise.
Front-End Protection Filters
Divider + TVS/RC parasitics vs. phase error; CM/DM filters for CT/shunt inputs.
Power-Fail Writes
PFAIL → debounce → atomic commit of key counters; ensure restart consistency.
Bidirectional / Grid-Tie
PV/storage four-quadrant energy with reverse-flow detection and tariff handling.
Calibration Flow
Multi-point (current/PF/temp) → solve gain/phase/offset → lock & write-protect.
Application-Focused
Single-Phase Smart Meter
Single-phase SoC + shunt/CT + RS-485/MBus/PLC + RTC/TOU + relay cut-off.
Three-Phase Industrial Meter
3-phase SoC with synchronous sampling, harmonics/events, Ethernet/RS-485 and large contactors.
Branch-Circuit Monitoring
Multi-channel AFEs + many shunts/CTs with Modbus/TCP gateway and alarms.
EV Charger
Legal-metrology AFE + contactor control + OCPP comms + leakage/thermal monitoring.
PV / Storage
Four-quadrant metering + anti-tamper (bypass/reverse) + grid-tie interfaces.
Smart Sockets / Rail Sockets
Single-chip metering + BLE/Wi-Fi/Thread + overpower trip + event logging.
Quick Cheats
I²R Power & Thermal
Shunt loss P=I²R; estimate temperature rise ΔT≈P×RθJA.
CT Range
Secondary voltage Vsec=Ipri/N × Rburden; avoid core saturation.
Power & Energy
Active power P=⟨v(t)i(t)⟩; energy E=∫P dt (discrete integration in metering ICs).
Power Factor
cosφ=P/S; low-PF accuracy depends on low noise & phase correction.
Harmonic Windowing
Configure window length vs. Fs (e.g., 10/12-cycle windows for 50/60 Hz).
