Temperature Conversion

Temperature Conversion (cross-cutting/units-atmos/temperature-conversion)

Use when the task is converting temperatures between the kelvin, celsius, fahrenheit, and rankine scales: absolute temperatures with the scale offsets and ratios, temperature differences with the degree sizes only, and the absolute zero limit of each scale. The general aerospace quantity conversion table (knots, pressure, Mach) lives in the unit-conversion leaf; this leaf is the dedicated temperature scale logic.

Domain quick reference

• Scale pivots: 0 C is 273.15 K, 32 F, and 491.67 R; absolute zero is 0 K, 0 R, -273.15 C, and -459.67 F.
• Celsius to kelvin adds 273.15; celsius to fahrenheit applies the 9/5 ratio plus the 32 offset; rankine uses fahrenheit-sized degrees from absolute zero.
• Degree sizes: one kelvin equals one celsius degree; one rankine equals one fahrenheit degree; one kelvin equals 9/5 rankine.
• Absolute temperature conversion routes every scale through kelvin, so the physical temperature is invariant across the scales.
• Temperature differences use only the degree sizes: a ten celsius degree change is an eighteen fahrenheit degree change.
• A temperature below the absolute zero of its scale is physically meaningless; the logic raises ValueError.

Workflow

1. Identify whether the input is an absolute temperature or a temperature difference: a difference carries no scale offset.
2. For an absolute temperature, call convert_temperature(value, from_unit, to_unit) with the unit letters k, c, f, or r.
3. For a temperature difference, call convert_delta(value, from_unit, to_unit) with the same unit letters.
4. Check the result against the absolute zero of the target scale before gating the thermal data exchange.

Pitfalls

• Applying the 32 offset to a temperature difference: only absolute temperatures carry the offset; a difference uses degree sizes only, so ten celsius degrees are eighteen fahrenheit degrees.
• Mixing up the degree sizes: one kelvin is 9/5 rankine, not 5/9.
• Using the wrong scale letter: the logic accepts k, c, f, and r only, case-insensitive; full names like kelvin raise ValueError.
• Accepting a temperature below absolute zero: the logic raises ValueError; zero kelvin and zero rankine are the lower bounds.
• Duplicating the unit-conversion leaf: general quantity conversion (knots, pressure, density, mass) belongs to unit-conversion; this leaf covers the temperature scales.

Behavior contract (gate 3)

The scale, offset, and delta logic is exercised by the gate 3 contract test: scripts/test_temperature_conversion.py against scripts/temperature_conversion_logic.py (stdlib unittest, offline). Run:

python3 scripts/test_temperature_conversion.py

Compliance

• NACA Report 824 is US government work (public domain); the pack anchor per standards-map.yaml. The four temperature scales and their conversion factors are common engineering conventions, not RTCA or SAE content; summary and formulas only.
• compliance: STANDARDS-REF, gated: false.