Single heat flux sensor arrangement

A method of measuring a core body temperature of a subject, comprising:

• attaching a sensor to the subject, the sensor comprising a heater, a thermally insulating layer of thermally insulating material, an inner temperature sensor arranged at an inner region of the thermally insulating layer, and an outer temperature sensor arranged at an outer region of the thermally insulating layer;
• determining a first equilibrium temperature of one of the inner temperature sensor or the outer temperature sensor, and subsequently activating the heater to heat the outer region of the thermally insulating layer of the sensor;
• determining a second equilibrium temperature of the one of the inner temperature sensor or the outer temperature sensor;
• subsequently calculating a value of thermal resistivity R0 of the subject according to
• R
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• 0
• =
• T
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• 12
• -
• T
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• 11
• T
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• 11
• -
• T
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• 21
• +
• T
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• 22
• -
• T
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• 12
• ·
• R
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• 1
• wherein T11 is a first inner temperature sensor temperature value, T12 is a second inner temperature sensor temperature value, T21 is a first outer temperature sensor temperature value, T22 is a second outer temperature sensor temperature value, and R1 is thermal resistivity of the thermally insulating layer;
• and
• calculating the core body temperature of the subject based on the calculated thermal resistivity value.

A heat flux sensor device comprising:

• a sensor configured to contact skin of a subject, the sensor comprising an thermally insulating layer, an inner thermistor at an inner region of the thermally insulating layer to be arranged adjacent to the skin, and an outer thermistor at an outer region of the thermally insulating layer, wherein the thermally insulating layer has a thermal resistivity R1;
• a heater configured to heat at least the outer region of the thermally insulating layer, and
• a processing unit programmed to:
• receive a first inner temperature value T11 from the inner thermistor at a first equilibrium temperature of the sensor,
• receive a first outer temperature value T21 from the outer thermistor at the first equilibrium temperature of the sensor,
• receive a second inner temperature value T12 from the inner thermistor at a second equilibrium temperature of the sensor higher than the first equilibrium temperature;
• receive a second outer temperature value T22 from the outer thermistor at the second equilibrium temperature of the sensor;
• and
• calculate a thermal resistivity value R0 of the subject according to:
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• T
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• 1
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• 2
• -
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• 1
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• 1
• T
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• 1
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• 1
• -
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• 2
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• 1
• +
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• 2
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• 2
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• 1
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• 2
• ·
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• 1.