Materials Resistivity/Conductivity Table implementation

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

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