Non-Contact Voltage Sensors Face Challenges in Accurate Measurement

Researchers at Kunming University have been working to address the challenges faced by non-contact voltage sensors, particularly in accurate measurement. The sensors, which use capacitive coupling to measure voltage, face difficulties in determining the division ratio due to variability in the probe-conductor coupling capacitance. This capacitance is influenced by factors such as the conductor's insulation material, radius, and relative position.

To overcome this challenge, the researchers proposed a sensor gain self-calibration method based on switching capacitors. This method involves obtaining multiple sets of real-time measurement outputs by connecting and switching different standard capacitors in parallel with the sensor's structural capacitance. The system is designed to simultaneously solve for the coupling capacitance and the voltage under test, achieving on-site autonomous calibration of the sensor gain. The researchers also designed a shielded coaxial probe structure and corresponding back-end processing circuitry to effectively suppress interference from stray electric fields in the surrounding space.

The experimental platform built to validate the method's effectiveness showed promising results within the 100-300 V power-frequency range. The reconstructed voltage amplitude showed a maximum relative error of 1.06% and a maximum phase error of 0.76 degrees. Harmonics were measurable up to the 50th order. Under inter-phase electric field interference, the maximum relative error of the reconstructed voltage amplitude was 1.34%, demonstrating significant shielding effectiveness. The results confirm the method's strong environmental adaptability and broad applicability across different conductor diameters.

Key Takeaways:

• The researchers proposed a sensor gain self-calibration method based on switching capacitors to address the challenges faced by non-contact voltage sensors.
• The method involves obtaining multiple sets of real-time measurement outputs by connecting and switching different standard capacitors in parallel with the sensor's structural capacitance.
• The system is designed to simultaneously solve for the coupling capacitance and the voltage under test, achieving on-site autonomous calibration of the sensor gain.
• The shielded coaxial probe structure and corresponding back-end processing circuitry effectively suppress interference from stray electric fields in the surrounding space.
• The experimental platform showed promising results within the 100-300 V power-frequency range.
• The reconstructed voltage amplitude showed a maximum relative error of 1.06% and a maximum phase error of 0.76 degrees.
• Harmonics were measurable up to the 50th order.
• Under inter-phase electric field interference, the maximum relative error of the reconstructed voltage amplitude was 1.34%, demonstrating significant shielding effectiveness.
• The results confirm the method's strong environmental adaptability and broad applicability across different conductor diameters.

Statistics:

• Maximum relative error of the reconstructed voltage amplitude: 1.06%
• Maximum phase error of the reconstructed voltage amplitude: 0.76 degrees
• Maximum relative error of the reconstructed voltage amplitude under inter-phase electric field interference: 1.34%
• Harmonics measurable up to: 50th order
• Conductor diameters measured: 6 mm2 to 35 mm2
• Measurement error controlled within: 1.57%

Sources:

• NewsRx. Findings from Kunming University Broaden Understanding of Electronics (Research On Non-contact Low-voltage Transmission Line Voltage Measurement Method Based On Switched Capacitor Calibration). Journal of Engineering. October 20, 2025; p 668.
• Research On Non-contact Low-voltage Transmission Line Voltage Measurement Method Based On Switched Capacitor Calibration. Electronics, 2025;14(18).