Abstract: Eddy current sensors are frequently used to detect and control non-electrical quantities such as pressure, temperature, displacement, and vibration. However, due to the influence of temperature, especially high temperature, they suffer from significant measurement errors. This paper proposes a closed-loop circuit testing system composed of deep negative feedback, which improves the stability and temperature drift suppression capability of eddy current sensors. By comparing tests under no-load and loaded conditions, the results demonstrate the effectiveness and advancement of the system. Keywords: Test principle; Test system; Negative feedback technology; Experimental analysis Abstract: Eddy current sensors are used to test and control various voltages, such as pressure, temperature, displacement, vibration, etc. However, temperature fluctuations, especially at high temperatures, can lead to serious measurement errors. This paper proposes a closed-loop circuit test system with negative feedback. This system improves the stability of the eddy current sensor and its ability to suppress temperature fluctuations. Comparing non-loaded and loaded conditions, the results demonstrate the system's availability and capability. Keywords: Test principle; Test system; Negative feedback technology; Experimental analysis 1 Test Principle Eddy currents refer to the induced electromotive force and closed-loop current generated within a metal body in a changing magnetic field. The generation of eddy currents inevitably consumes some magnetic field energy, causing a change in the impedance of the coil generating the magnetic field. Eddy current sensors are based on this eddy current effect. As shown in Figure 1, when an alternating current i flows through the coil l, an alternating magnetic field H is generated around the coil. An induced electromotive force is generated in the metal body s placed in the magnetic field, forming an eddy current. This eddy current will inevitably cause a change in the coil impedance. The magnitude of the coil impedance z is related to the resistivity ρ, permeability μ, size factor r, excitation frequency f, and distance x between the coil and the metal body being measured. The coil impedance z can be expressed by the following function [1]: For details, please click: Application of negative feedback technology in eddy current sensor detection