Source: https://guthlabs.ai/docs/instruments/materials-resistivity-conductivity-table/implementation/

instrument implementation / implementation-contract

# Materials Resistivity/Conductivity Table implementation

A source-bound implementation contract for Materials Resistivity/Conductivity Table; 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**: t7-001

**Effect**: Computation or source lookup only

## Input and validation requirements

- Area equal to zero causes division by zero; negative length or area must be rejected.

- Unknown material or missing table row must produce an explicit lookup error rather than a default value.

- The table must define valid temperature ranges; extrapolating the linear correction without bounds can produce inaccurate or even nonphysical results.

- The table convention and material grade must be retained with each value because copper and aluminum values vary by purity, alloy, annealing, and reference temperature.

- Unit ambiguity is hazardous: using mm^2 or cm^2 directly as m^2 produces errors of factors of 10^6 or 10^4.

- The blank honest_label is a concern: the instrument should state that temperature adjustment is an approximate linear model and that table values are nominal reference values, not universal material constants.

## 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",
    "length": 10,
    "length_unit": "m",
    "area": 1,
    "area_unit": "mm^2",
    "temperature": 20,
    "temperature_unit": "°C"
  },
  "expected_outputs": {
    "resistivity_ohm_m": 1.68e-8,
    "temperature_coefficient_per_C": 0.00393,
    "resistance_at_20C_ohm": 0.168,
    "adjusted_resistance_ohm": 0.168
  },
  "reference_data": {
    "material": "copper",
    "reference_temperature_C": 20,
    "resistivity_ohm_m": 1.68e-8,
    "temperature_coefficient_per_C": 0.00393,
    "source_convention": "CRC Handbook / widely tabulated standard value"
  },
  "working": "A=1 mm^2=1×10^-6 m^2. R20=ρL/A=(1.68×10^-8 Ω·m×10 m)/(1×10^-6 m^2)=0.168 Ω. Temperature factor=1+0.00393×(20−20)=1. Therefore R(20 °C)=0.168×1=0.168 Ω."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/materials-resistivity-conductivity-table/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/materials-resistivity-conductivity-table/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/materials-resistivity-conductivity-table/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`