"""Thermocouple scaling for DAQ: voltage → °C with cold-junction compensation."""
from enum import Enum
import thermocouples as tc
from instro.daq.scaling.scaling import Scaler
[docs]
class TC_TYPE(Enum):
B = "B"
E = "E"
J = "J"
K = "K"
N = "N"
R = "R"
S = "S"
T = "T"
[docs]
class TC_UNIT(Enum):
CELSIUS = "degC"
KELVIN = "K"
FAHRENHEIT = "degF"
RANKINE = "degR"
[docs]
def kelvin_to_unit(temp_k: float, unit: TC_UNIT) -> float:
"""Convert a Kelvin temperature to ``unit``."""
match unit:
case TC_UNIT.CELSIUS:
return temp_k - 273.15
case TC_UNIT.KELVIN:
return temp_k
case TC_UNIT.FAHRENHEIT:
return temp_k * 9 / 5 - 459.67
case TC_UNIT.RANKINE:
return temp_k * 9 / 5
case _:
raise AssertionError(f"unhandled TC_UNIT {unit}")
[docs]
def unit_to_kelvin(temp: float, unit: TC_UNIT) -> float:
"""Convert a temperature in ``unit`` to Kelvin."""
match unit:
case TC_UNIT.CELSIUS:
return temp + 273.15
case TC_UNIT.KELVIN:
return temp
case TC_UNIT.FAHRENHEIT:
return (temp + 459.67) * 5 / 9
case TC_UNIT.RANKINE:
return temp * 5 / 9
case _:
raise AssertionError(f"unhandled TC_UNIT {unit}")
[docs]
class ThermocoupleSensor(Scaler):
"""Thermocouple voltage → °C with cold-junction compensation.
>>> ThermocoupleSensor(TC_TYPE.K, cjc_temp=25.0) # Type K, 25 °C reference junction
"""
def __init__(self, type: TC_TYPE, cjc_temp: float):
"""Initialize the thermocouple sensor.
Args:
type: Thermocouple type (B/E/J/K/N/R/S/T).
cjc_temp: Cold-junction reference temperature in °C.
"""
self._type = type
self._cjc = cjc_temp
self._tc = tc.get_thermocouple(self._type.value)
[docs]
def scale(self, raw: float | int) -> float:
"""Voltage (volts or millivolts per the ``thermocouples`` library) → temperature (°C)."""
return self._tc.volt_to_temp_with_cjc(voltage=raw, ref_temp=self._cjc)
@property
def units(self) -> str:
return "degC"
[docs]
class InverseThermocoupleSensor(Scaler):
"""Temperature (°C) → voltage with cold-junction compensation — inverse of ``ThermocoupleSensor``.
>>> InverseThermocoupleSensor(TC_TYPE.K, cjc_temp=25.0) # Type K, 25 °C reference junction
"""
def __init__(self, type: TC_TYPE, cjc_temp: float):
"""Initialize the inverse thermocouple sensor.
Args:
type: Thermocouple type (B/E/J/K/N/R/S/T).
cjc_temp: Cold-junction reference temperature in °C.
"""
self._type = type
self._cjc = cjc_temp
self._tc = tc.get_thermocouple(self._type.value)
[docs]
def scale(self, raw: float | int) -> float:
"""Temperature (°C) → voltage with cold-junction compensation."""
return self._tc.temp_to_volt(raw) - self._tc.temp_to_volt(self._cjc)
@property
def units(self) -> str:
return "V"
instro