A temperature-humidity chamber, comprising:
- a thermal insulation wall surrounding a predetermined measurement space;
- a hygrometer that measures a humidity of the measurement space defined by the thermal insulation wall;
- a temperature and humidity adjustment section that adjusts at least one of a humidity and a temperature within the measurement space on a basis of a result of measurement by the hygrometer;
- wherein the hygrometer includes:
- a heat transfer section having a first end located in the measurement space and a second end opposite to the first end and external of the measurement space;
- a heat transfer section temperature sensor provided in the measurement space to detect a temperature of the heat transfer section;
- a measurement space temperature sensor provided in the measurement space at a position spaced from the heat transfer section to detect a temperature of the measurement space;
- a heat release amount control unit having a power supply unit that outputs a regulated electricity, a contact portion contacting the second end of the heat transfer section and a release portion exposed to the outside space for releasing heat from the heat transfer section to the outside space, the heat release amount control unit being controllable to release a prescribed amount of heat from the release portion to the outside space when powered by the power supply unit;
- a computation device that calculates a humidity of the measurement space,
- wherein the computation device stores (i) a first formula expressing a relation between a temperature of the heat transfer section, a temperature of the measurement space, an amount of heat released to the outside space from the release portion and a water vapor pressure of the measurement space, (ii) a second formula for calculating a humidity of the measurement space from a water vapor pressure of the measurement space and a saturated water vapor pressure at the temperature of the measurement space, and (iii) data in which a temperature and a saturated water vapor pressure at each temperature are associated, the first formula being based on a base formula associating a sum of sensible heat and latent heat with the amount of heat released to the outside space from the release portion, the sensible heat being a heat that enters the heat transfer section from the measurement space, the latent heat being a heat supplied to the heat transfer section by dew formation on the heat transfer section, the base formula expressing the sum that equals the amount of heat released to the outside space from the release portion, and
- the computation device includes a first calculating section and a second calculating section, the first calculating section being configured to calculate a water vapor pressure of the measurement space, using the first formula, from a temperature of the heat transfer section detected by the heat transfer section temperature sensor, a temperature of the measurement space detected by the measurement space temperature sensor and the prescribed amount of heat released to the outside space from the release portion when dew formation is occurring in the first end of the heat transfer section located within the measurement space in a state where the amount of heat released to the outside space from the release portion is controlled to the prescribed amount when the heat release amount control unit is powered by the power supply unit, and the second calculating section being configured to calculate a humidity of the measurement space, using the second formula, from the water vapor pressure of the measurement space calculated using the first formula and the saturated water vapor pressure at the temperature of the measurement space obtained using the data.