Grashof incubator has continuously changed for improvement from A-type to G-type as an effort to increase quality both in physical and thermal terms. The unchanging part is the use of an analog thermostat as an electrical cut-off based on the upper limit of temperature. The accuracy and uniformity of the analog thermostats are not reliable. This is the main cause of the performance of several grashof incubators that are not uniform with each other. Changes in the heating chamber design and the use of TD-W1209 digital thermostats that are applied to the H-type prototype grashof incubator are intended so that their performance is following SNI IEC 60601-2-19: 2014 (Indonesia National Standard) criteria. By using these standards, it can be seen the effect of the digital thermostat on heat performance, especially the accuracy of temperature and uniformity in the baby's cabin of G-type and H-type. From the results of changes in H-type, the average reading deviation in the device is only about-0.65oC (from +/-1.5oC tolerance). Uniformity in-cabin temperature increased to 93,8% in H-type from previously only 88,1% on G-type. Modification of the heating chamber design and applying W1209 digital thermostats, placing the H-type in good accordance to the SNI IEC 60601-2-19: 2014 criteria.