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Commit b25622f

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Use SI constants in CO unit converter (home-assistant#153187)
1 parent e887d5e commit b25622f

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3 files changed

+24
-10
lines changed

3 files changed

+24
-10
lines changed

‎homeassistant/util/unit_conversion.py‎

Lines changed: 19 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -91,6 +91,17 @@
9191
_FLUID_OUNCE_TO_CUBIC_METER = _GALLON_TO_CUBIC_METER / 128 # 128 fl. oz. in a US gallon
9292
_CUBIC_FOOT_TO_CUBIC_METER = pow(_FOOT_TO_M, 3)
9393

94+
# Gas concentration conversion constants
95+
_IDEAL_GAS_CONSTANT = 8.31446261815324 # m3⋅Pa⋅K−1⋅mol−1
96+
# Ambient constants based on European Commission recommendations (20 °C and 1013mb)
97+
_AMBIENT_TEMPERATURE = 293.15 # K (20 °C)
98+
_AMBIENT_PRESSURE = 101325 # Pa (1 atm)
99+
_AMBIENT_IDEAL_GAS_MOLAR_VOLUME = ( # m3⋅mol−1
100+
_IDEAL_GAS_CONSTANT * _AMBIENT_TEMPERATURE / _AMBIENT_PRESSURE
101+
)
102+
# Molar masses in g⋅mol−1
103+
_CARBON_MONOXIDE_MOLAR_MASS = 28.01
104+
94105

95106
class BaseUnitConverter:
96107
"""Define the format of a conversion utility."""
@@ -169,14 +180,17 @@ def _are_unit_inverses(cls, from_unit: str | None, to_unit: str | None) -> bool:
169180

170181

171182
class CarbonMonoxideConcentrationConverter(BaseUnitConverter):
172-
"""Convert carbon monoxide ratio to mass per volume."""
183+
"""Convert carbon monoxide ratio to mass per volume.
184+
185+
Using ambient temperature of 20°C and pressure of 1 ATM.
186+
"""
173187

174188
UNIT_CLASS = "carbon_monoxide"
175189
_UNIT_CONVERSION: dict[str | None, float] = {
176-
CONCENTRATION_PARTS_PER_MILLION: 1,
177-
# concentration (mg/m3) = 0.0409 x concentration (ppm) x molar mass
178-
# Carbon monoxide molar mass: 28.01 g/mol
179-
CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER: 0.0409*28.01,
190+
CONCENTRATION_PARTS_PER_MILLION: 1e6,
191+
CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER: (
192+
_CARBON_MONOXIDE_MOLAR_MASS/_AMBIENT_IDEAL_GAS_MOLAR_VOLUME*1e3
193+
),
180194
}
181195
VALID_UNITS = {
182196
CONCENTRATION_PARTS_PER_MILLION,

‎tests/components/sensor/test_recorder.py‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3626,7 +3626,7 @@ async def test_compile_hourly_statistics_changing_units_3(
36263626
13.050847,
36273627
-10,
36283628
30,
3629-
1.145609,
3629+
1.16441,
36303630
),
36313631
(
36323632
"carbon_monoxide",
@@ -3636,7 +3636,7 @@ async def test_compile_hourly_statistics_changing_units_3(
36363636
13.050847,
36373637
-10,
36383638
30,
3639-
1 / 1.145609,
3639+
1 / 1.16441,
36403640
),
36413641
(None, "%", None, "unitless", 13.050847, -10, 30, 0.01),
36423642
(None, "W", "kW", "power", 13.050847, -10, 30, 0.001),

‎tests/util/test_unit_conversion.py‎

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -119,7 +119,7 @@
119119
CarbonMonoxideConcentrationConverter: (
120120
CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
121121
CONCENTRATION_PARTS_PER_MILLION,
122-
1.145609,
122+
1.16441,
123123
),
124124
ConductivityConverter: (
125125
UnitOfConductivity.MICROSIEMENS_PER_CM,
@@ -291,13 +291,13 @@
291291
(
292292
1,
293293
CONCENTRATION_PARTS_PER_MILLION,
294-
1.145609,
294+
1.16441,
295295
CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
296296
),
297297
(
298298
120,
299299
CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER,
300-
104.74778,
300+
103.05655,
301301
CONCENTRATION_PARTS_PER_MILLION,
302302
),
303303
],

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