Abstract: An enthalpy calculator outputs a value of enthalpy directly calculated from two measured items such as dry bulb temperature and relative humidity, and includes: a humidity sensor for converting relative humidity into an electrical signal; a temperature sensor for converting dry bulb temperature into an electrical signal; and arithmetic units for outputting the calculated enthalpy value as an electrical signal after performing a calculation based on the signals input by the temperature sensor 12 and the humidity sensor 5 in accordance with the following equation:i=at.psi.+bt+c.psi.+dwhereina, b, c, and d are preselected constants, and:t: dry bulb temperature (.degree.C.).psi.: relative humidity (%),a, b, c, and d being selected so that .vertline.i-i.sub.0 .vertline..ltoreq.0.5 within a fixed temperature range if:i.sub.0 =0.240t+(597.3+0.441t)xandx=0.622.multidot..psi..multidot.h/P-.psi..multidot.

Abstract: An enthalpy calculator unit outputs a value of enthalpy directly from two measured parameters, such as dry bulb temperature and relative humidity, and includes a humidity sensor 17 for converting a measured relative humidity into an electrical signal; temperature sensors for converting a measured temperature into electrical signals; and arithmetic units for calculating the enthalpy and for outputting electrical signal corresponding thereto after performiing a calculation based on the signals input by the sensors in accordance with the following equation:i=(ae.sup.bt -c)(t+d).psi.+mt+nwherea, b, c, d, m, and n are constants, and:t: dry bulb temperature (.degree.C.).psi.: relative humidity (%),and a, b, c, d, m, and n are selected so that .vertline.i-i.sub.0 .vertline..ltoreq.0.5 within a fixed temperture range if:i.sub.0 =0.240t+(597.3+0.441t)xx=0.622.multidot..psi..multidot.h/(P-.psi..multidot.h)whereP: atmospheric pressureh: saturated vapor pressure under the atomspheric pressure P.