Voltage Drop Calculator (wire run) 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

t7-076

Effect

Computation or source lookup only

Input and validation requirements

A zero source voltage produces a finite voltage-drop result but makes the required percentage and guideline pass/fail result undefined. The instrument also has a material one-way-versus-loop-length ambiguity unless the length convention is explicitly captured.

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": {
    "length": 100,
    "length_unit": "ft",
    "current": 15,
    "current_unit": "A",
    "conductor": "copper",
    "gauge": "12 AWG",
    "area_mm2": 3.31,
    "resistivity_ohm_m": 1.68e-8,
    "phase_config": "DC",
    "source_voltage": 120,
    "source_voltage_unit": "V"
  },
  "expected_outputs": {
    "voltage_drop_V": 4.6411,
    "voltage_drop_percent": 3.8676,
    "pass_3_percent": false,
    "pass_5_percent": true
  },
  "reference_data": {
    "copper_resistivity_ohm_m_20C": 1.68e-8,
    "copper_resistivity_source_convention": "widely tabulated standard value; CRC/NIST textbook value at approximately 20 °C",
    "awg_12_copper_area_mm2": 3.31,
    "awg_area_source_convention": "widely tabulated standard AWG cross-sectional-area value",
    "feet_to_metres": 0.3048,
    "feet_to_metres_source_convention": "exact SI/international definition"
  },
  "working": "R_per_m = rho / area = 1.68e-8 ohm·m / (3.31e-6 m²) = 0.00507553 ohm/m. R_per_ft = 0.00507553 × 0.3048 = 0.00154702 ohm/ft. DC voltage drop = 2 × L × I × R_per_ft = 2 × 100 ft × 15 A × 0.00154702 ohm/ft = 4.64106 V, rounded to 4.6411 V. Drop percentage = 4.64106 / 120 × 100 = 3.86755%, rounded to 3.8676%. Since 3.8676% > 3%, the 3% check fails; since 3.8676% ≤ 5%, the 5% check passes."
}

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