Source: https://guthlabs.ai/docs/instruments/oven-temperature-converter/

instrument / verified-clean

# Oven Temperature Converter

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/oven-temperature-converter/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/oven-temperature-converter/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/oven-temperature-converter/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/oven-temperature-converter/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Everyday & Life

**Tranche**: tranche-2

**Evidence ID**: t2-031

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The basic Fahrenheit/Celsius arithmetic is sound, but the instrument cannot receive a single unambiguous implementation specification because the inverse conversion formula, gas-mark lookup data, convection adjustment unit convention, adjustment direction, rounding policy, and cooking-time input are not fully defined. The honest-label warning correctly identifies the convection adjustment as a heuristic, but it should also disclose the unit-rule discrepancy and gas-mark table assumption.

### Formula and scope findings

- The Fahrenheit-to-Celsius formula is correct: °C=(°F−32)×5/9.

- The specification claims conversion in both directions but does not state the inverse formula: °F=°C×9/5+32.

- The convection adjustment is internally inconsistent across units: subtracting 25°F is equivalent to subtracting approximately 13.89°C, not 20°C. Subtracting 20°C is equivalent to subtracting 36°F.

- The adjustment direction is ambiguous: it is not specified whether an input conventional temperature should produce a suggested convection temperature, or whether an input convection temperature should produce a conventional equivalent.

- The gas-mark conversion is delegated to a table but the actual table, supported fractional gas marks, rounding policy, and regional standard are not specified.

- The approximately 25% time reduction cannot produce an adjusted cooking time because no cooking-time input is defined.

### Unit assumptions

- Fahrenheit and Celsius temperatures use the standard affine conversion formulas; temperature differences use a 5/9 scale ratio.

- For these test vectors, the convection rule is interpreted as subtracting 25°F when the source temperature is Fahrenheit, or subtracting 20°C when the source temperature is Celsius; these are not equivalent rules.

- Gas mark 6 is assumed to map to 400°F, approximately 204.44°C, using a common UK gas-mark table.

- Displayed Celsius values are rounded to two decimal places; intermediate arithmetic uses full precision.

- A conventional-oven input is interpreted as requesting a suggested convection-oven setting.

- The 25% time figure is interpreted as a suggested percentage reduction, not an exact adjusted duration.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

The spec has a material convention ambiguity: applying the stated −20 °C rule versus the stated −25 °F rule produces different convection temperatures. At extreme finite inputs, JavaScript precision also erases the 25 °F adjustment.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "inputs": {
    "temperature": 350,
    "unit": "°F",
    "oven_type": "conventional"
  },
  "expected_outputs": {
    "converted_celsius": 176.67,
    "suggested_convection_fahrenheit": 325,
    "suggested_convection_celsius": 162.78,
    "suggested_time_reduction_percent": 25
  },
  "working": "1. Convert temperature: (350−32)×5/9 = 318×5/9 = 1590/9 = 176.6667°C, which rounds to 176.67°C. 2. Apply the Fahrenheit convection rule: 350−25 = 325°F. 3. Convert the suggested convection setting: (325−32)×5/9 = 293×5/9 = 1465/9 = 162.7778°C, which rounds to 162.78°C. 4. The heuristic time suggestion is a 25% reduction."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

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

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche2/tranche2-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`