An improved version of a low-temperature double calorimeter for the temperature range 20-320 K is presented. The temperature of the adiabatic shield is increased at a programmable rate, while the temperature differences to the samples are regulated to zero. Temperature control and data acquisition are achieved by software algorithms integrated in a single computer program. The apparatus yields a typical precision Delta C-p/C-p of 10(-3) with approximate to 50 data K-1.