Cable Shielding Effectiveness
SE = 8.686 × t × √(πfµσ)
Quick answer
This calculator solves SE = 8.686 × t × √(πfµσ) for SE. With Frequency 10 MHz, Permeability (H/m) 0.5 H/m, Conductivity (S/m) 1.1 S/m, Shield Thickness 10 mm, the result is 361.1 dB.
Calculator
Formula
Description
Cable shielding attenuates electromagnetic interference through absorption and reflection. This simplified formula shows that shielding effectiveness increases with frequency, shield conductivity, permeability, and shield thickness. At low frequencies, magnetic shielding is difficult because the absorption loss is small, requiring high-permeability materials like mu-metal. At high frequencies, even thin copper or aluminum shields provide excellent attenuation. Braided shields are the most common type, offering good flexibility and moderate SE (40-90 dB), while solid tube shields provide the best performance (>100 dB).
Variables
- SE — Shielding effectiveness (dB)
- f — Frequency (Hz)
- µ — Permeability of shield material (H/m)
- σ — Conductivity of shield material (S/m)
- t — Shield thickness (m)
Practical Notes
Braided cable shields have coverage percentages of 60-98%, and SE improves with higher coverage. Double-shielded cables (braid + foil) achieve 90-120 dB SE. For copper: σ = 5.8×10⁷ S/m, µ = µ₀ = 4π×10⁻⁷ H/m. Cable shield grounding is critical: ground at one end only for low frequencies (to avoid ground loops) or at both ends for high frequencies (to maintain shield current return path).
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| f | Frequency | MHz | Hz, kHz, MHz, GHz |
| mu | Permeability (H/m) | — | H/m |
| sigma | Conductivity (S/m) | — | S/m |
| t | Shield Thickness | mm | mm |
Step by step
- 1. What you know: Frequency 10 MHz, Permeability (H/m) 0.5 H/m, Conductivity (S/m) 1.1 S/m, Shield Thickness 10 mm
- 2. The relation: SE = 8.686 × t × √(πfµσ)
- 3. Substitute: f = 10 MHz, mu = 0.5 H/m, sigma = 1.1 S/m, t = 10 mm
- 4. Result: SE = 361.1 dB
Worked examples
Minimum range
Given: Frequency 100 kHz, Permeability (H/m) 0.025 H/m, Conductivity (S/m) 0.055 S/m, Shield Thickness 0.1 mm
Result: SE = 0.01805 dB
Low range
Given: Frequency 1 MHz, Permeability (H/m) 0.25 H/m, Conductivity (S/m) 0.55 S/m, Shield Thickness 1 mm
Result: SE = 5.709 dB
Typical
Given: Frequency 10 MHz, Permeability (H/m) 0.5 H/m, Conductivity (S/m) 1.1 S/m, Shield Thickness 10 mm
Result: SE = 361.1 dB
High range
Given: Frequency 100 MHz, Permeability (H/m) 0.8 H/m, Conductivity (S/m) 1.76 S/m, Shield Thickness 100 mm
Result: SE = 18270 dB
Maximum range
Given: Frequency 1 GHz, Permeability (H/m) 8 H/m, Conductivity (S/m) 17.6 S/m, Shield Thickness 1000 mm
Result: SE = 5.78 × 10⁶ dB
How SE changes with Frequency
| Frequency (input) | SE (result) |
|---|---|
| 1 MHz | 114.2 dB |
| 2.5 MHz | 180.5 dB |
| 5 MHz | 255.3 dB |
| 7.5 MHz | 312.7 dB |
| 10 MHz | 361.1 dB |
| 15 MHz | 442.2 dB |
| 20 MHz | 510.6 dB |
| 40 MHz | 722.1 dB |
| 70 MHz | 955.3 dB |
| 100 MHz | 1142 dB |
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<p><a href="https://vbatpower.com/formulas/cable-shielding/">Cable Shielding Effectiveness</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Cable Shielding Effectiveness?
Use SE = 8.686 × t × √(πfµσ). With Frequency 10 MHz, Permeability (H/m) 0.5 H/m, Conductivity (S/m) 1.1 S/m, Shield Thickness 10 mm, SE works out to 361.1 dB.
What is the formula for Cable Shielding Effectiveness?
The formula is SE = 8.686 × t × √(πfµσ). Cable shielding attenuates electromagnetic interference through absorption and reflection.
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