Source: https://guthlabs.ai/docs/instruments/wentworth-grain-size-classifier/implementation/

instrument implementation / implementation-contract

# Wentworth Grain-Size Classifier implementation

A source-bound implementation contract for Wentworth Grain-Size Classifier; 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**: t7-103

**Effect**: Computation or source lookup only

## Input and validation requirements

The zero-diameter input produces an undefined logarithm and must be rejected. The specification also does not explicitly define exact class-boundary endpoint ownership or enforce the diameter unit, creating boundary and unit-convention failure risks.

## 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": {
    "grain_diameter": 1,
    "unit": "mm"
  },
  "expected_outputs": {
    "phi": 0,
    "class_name": "very coarse sand"
  },
  "reference_data": {
    "rows": [
      {
        "diameter_mm": 1,
        "phi_boundary": 0,
        "class_name": "very coarse sand",
        "source_convention": "Udden-Wentworth grain-size scale, widely tabulated standard value"
      },
      {
        "diameter_mm": 2,
        "phi_boundary": -1,
        "class_name": "granule",
        "source_convention": "Udden-Wentworth grain-size scale, widely tabulated standard value"
      }
    ],
    "boundary_convention": "[lower diameter, upper diameter)"
  },
  "working": "φ = -log2(1.0) = -log2(1) = 0.0. The diameter is at the 1.0 mm boundary and, using [lower, upper), belongs to the 1–2 mm very coarse sand interval."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/wentworth-grain-size-classifier/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/wentworth-grain-size-classifier/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/wentworth-grain-size-classifier/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`