Source: https://guthlabs.ai/docs/instruments/skin-effect-skin-depth-calculator/implementation/

instrument implementation / implementation-contract

# Skin Effect / Skin Depth Calculator implementation

A source-bound implementation contract for Skin Effect / Skin Depth Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-092

**Effect**: Computation or source lookup only

## Input and validation requirements

The instrument can fail or mislead at zero or negative frequency, and it lacks a defined full Bessel-function calculation for the thin/intermediate-conductor branch. Unit and diameter-versus-radius ambiguity can also change the reported resistance ratio substantially.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "material": "copper",
    "resistivity_ohm_m": 1.68e-8,
    "relative_permeability": 1,
    "frequency_hz": 1000000,
    "wire_diameter_m": 0.01
  },
  "expected_outputs": {
    "skin_depth_m": 0.00006523,
    "skin_depth_um": 65.23,
    "rac_rdc_ratio": 38.33
  },
  "reference_data": {
    "copper_resistivity_ohm_m_20C": 1.68e-8,
    "copper_resistivity_source_convention": "widely tabulated standard value; CRC/IEC textbook value at 20 °C",
    "mu0_H_per_m": 0.0000012566370614,
    "mu0_source_convention": "widely tabulated standard value, μ0=4π×10^-7 H/m",
    "copper_relative_permeability": 1,
    "relative_permeability_source_convention": "widely tabulated standard value for nonmagnetic copper"
  },
  "working": "μ=μrμ0=1×1.2566370614×10^-6=1.2566370614×10^-6 H/m. δ=sqrt(ρ/(πfμ))=sqrt(1.68×10^-8/(π×1.00×10^6×1.2566370614×10^-6))=sqrt(4.2555×10^-9)=6.523×10^-5 m=65.23 μm. d/(4δ)=0.010/(4×6.523×10^-5)=0.010/2.6092×10^-4=38.33. Here d/δ≈153.3, so the high-frequency approximation is appropriate."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/skin-effect-skin-depth-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/skin-effect-skin-depth-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/skin-effect-skin-depth-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`