Shunhai Technology: Strategy for Improving the Anti-jamming Capability of Precision Alloy Resistors in the Electronic Field
Date：2025-12-16
Viewed：4
As a critical component in electronic circuits, alloy resistors' anti-interference capability directly impacts circuit stability. This is especially critical in high-precision measurement and medical equipment applications where signal purity is paramount. To enhance their anti-interference performance, a multi-dimensional approach is required, including electromagnetic compatibility (EMC) design, structural optimization, and environmental isolation.
1. Electromagnetic shielding: blocking the invasion of external electromagnetic radiation
Electromagnetic interference from external environments (e.g., electromagnetic waves generated by motors or high-frequency devices) can easily enter the alloy resistor through spatial coupling, causing abnormal resistance fluctuations. Encasing the alloy resistor with a metal shielding cover effectively blocks electromagnetic radiation.
Shielding material selection: The shield is made of high-conductivity copper or nickel-plated steel plate, utilizing the "eddy current effect" to convert electromagnetic energy into heat for dissipation. The shielding efficiency must exceed 60dB (meaning the external electromagnetic intensity is reduced to 1/1000 of its original level).
Grounding design: The shielding cover must be grounded at a single point to prevent the 'antenna effect'. The grounding wire should be short and thick (with a cross-sectional area of ≥2.5mm²), directly connected to the circuit system's grounding busbar to ensure rapid discharge of induced charges on the shielding cover.
2. Circuit Filtering: Conduction Path of Conduction Interference Suppression
The main interference of alloy resistor is power supply noise and high frequency signal coupling.
Power supply filtering: A LC filter circuit is formed by connecting a magnetic bead (for high frequency) and an electrolytic capacitor (for low frequency) in series in the alloy resistor power supply circuit. For example, a 100μH magnetic bead paired with a 10μF electrolytic capacitor can suppress power supply noise from 100kHz to 1GHz, keeping the voltage ripple across the resistor ≤10mV.
Signal filtering: When using alloy resistors in detection circuits (e.g., current sampling), a RC absorption circuit (100Ω resistor + 100pF capacitor) must be connected in parallel at the signal output to suppress high-frequency interference, ensuring a signal-to-noise ratio (SNR) of ≥60dB for sampled signals.
3. Structure Optimization: Reduce the Coupling Path Between Itself and the Outside World
Wiring design: The lead of alloy resistor should be short and straight to avoid forming loop wiring (which is prone to electromagnetic induction). If long lead is required, twisted pair wire (twist pitch ≤10mm) should be used to reduce electromagnetic coupling coefficient by canceling each other's magnetic field.
For isolation installation, mount the alloy resistor on an insulating bracket (e.g., ceramic bracket) with at least 5mm clearance from the metal chassis to minimize conducted interference. When sharing the PCB with high-power components (e.g., relays or motors), maintain a 10mm isolation zone and separate them with grounded copper foil.
4. MATERIALS AND TECHNOLOGY: REDUCING INTERFERENCE SENSITIVITY FROM THE SOURCE
Improvement of alloy materials: Adding elements such as nickel and chromium to resistive alloys can enhance their electromagnetic compatibility. For instance, a manganese-copper alloy (84% copper, 12% manganese, 4% nickel) is over 30% less sensitive to high-frequency electromagnetic interference compared to pure copper resistors.
Encapsulation process: Ceramic encapsulation (e.g., 96% alumina ceramic) is employed to block interference conduction through its high insulation properties. The interior is filled with epoxy resin (containing iron powder magnetic core) to absorb low-frequency magnetic field interference, ensuring the resistor's magnetic sensitivity remains ≤10ppm/mT.
5. Grounding and Grounding Grid Design: Avoiding Ground Potential Interference
Single-point grounding: The grounding terminal of the alloy resistor circuit must be independently connected to the system's "star grounding" point. This prevents sharing the grounding circuit with high-power equipment and avoids interference caused by ground potential differences. The grounding conductor's resistance must be ≤0.1Ω to ensure interference currents do not flow through the resistance circuit.
Floating ground design: In precision measurement circuits, the module containing alloy resistors is isolated from the system ground (using optocouplers or isolated amplifiers), ensuring the potential difference between the module ground and the system ground is ≤10mV, thereby fundamentally eliminating ground loop interference.
Through these strategies, alloy resistors maintain stability in complex electromagnetic environments: in industrial settings (EMI intensity 10V/m), resistance fluctuations remain ≤0.01%; in medical devices, they withstand strong interference sources like defibrillators to ensure accurate and reliable monitoring signals. The core of anti-interference design lies in blocking interference coupling paths—whether through space radiation, conductive coupling, or ground potential differences—targeted blocking ensures the alloy resistor operates consistently.
