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Reverse Power Detection Test — MSO5000 Liveview Validation

Scenario: Zero Net Power Consumption, Net Energy Return

This experiment demonstrates the ability of various measurement tools to correctly detect reverse real power (i.e., energy being fed back to the source) in a test circuit specifically designed to consume zero net power but return energy to its input terminals over time.

Purpose

To verify if consumer-grade or professional instruments are capable of correctly identifying and quantifying negative real power in scenarios such as:

  • Resonant LC networks,
  • Capacitive injection,
  • Non-linear energy-return systems.

Test Setup

  • Circuit Goal: No net energy consumed; periodic energy return to source.
  • Voltage and Current Channels: Precisely synchronized using the Rigol MSO5000 series oscilloscope.
  • Measurement Methods:
  • Direct waveform capture with oscilloscope (shunt-based).
  • Electromechanical analog wattmeter (torque-based).
  • CT-based smart meter and consumer plug meter (e.g., EMONIO P3).
  • MSO5000 Liveview Power Analysis (custom real-time P/Q/S computation).

Results Summary

Test Condition Rigol Oscilloscope MSO5000 Power Analysis EMONIO P3 Smart Meter Mechanical Wattmeter
Load: ON -11W -13W 13W, 0VAR -Q, +P stopped (0 W)
Load: OFF -12W -13W -12W, -358VAR +Q, +P stopped (0 W)
  • Measurements from Rigol and MSO5000 Liveview clearly show negative real power.
  • Smart meters fail to detect direction — falsely show positive power with reactive component.
  • Mechanical wattmeter stops (indicating 0 W net torque), consistent with zero net consumption.
  • EMONIO P3 shows conflicting values, likely due to CT inaccuracies.

Date of test: 2025-08-04

Why CT-Based Devices Fail in This Scenario

  • Current Transformers (CTs) are AC-only and do not convey direction of current.
  • Without high-resolution, synchronized voltage sampling, they cannot resolve phase angles accurately.
  • Many consumer smart meters clip or average near-zero or bidirectional power flows to zero or small values.
  • Reverse power often gets filtered or ignored by firmware logic to avoid confusing the end-user.

Key Insights

  • Shunt-based or waveform-based systems (like the MSO5000 + Liveview) capture full time-domain polarity and phase information.
  • Reverse power can only be accurately measured if both voltage and current are sampled simultaneously and with sufficient resolution.
  • Mechanical wattmeters still outperform most digital consumer meters when it comes to true power direction detection.

Conclusion

This test validates that the MSO5000 Liveview power analysis tool — built on waveform-level analysis — provides physically correct and direction-sensitive power measurements.

It outperforms several commercial devices by: - Respecting waveform phase, - Avoiding false assumptions based on RMS-only math, - Accurately detecting reverse power flow.

Such capabilities are critical for advanced applications, including: - Reactive compensation tuning, - Energy harvesting validation, - Power quality analysis in complex loads.

Author: MSO5000 Liveview Development Team*