Two simple and novel pyrheliometers have been designed and constructed based on anew methodology to measure solar irradiance. They are respectively the double-sensor and the single-sensor methods. The sensor surface is made of heavily oxidized stainless steel foil, which is formed as a circular disk and thermally joined to a large stainless steel ring acting as a heat sink. For the former method, through respectively measuring the temperature differences between the two sensors＇ center points and the heat sink, the incident solar irradiance and the heat-loss coefficient on the sensor＇s surface can be determined using thermal equilibrium equations under steady-state conditions. For the latter method, the ratio of solar irradiance to the temperature difference between the single-sensor＇s point center and the heat sink is a constant. The constant depends on the geometric dimensions, thermophysical properties of the sensor and the heat-loss coefficient. It can be calibrated using a standard pyrheliometer. Comparing a calibrated TMI Mark-VI pyrheliometer with the double-sensor pyrheliometer, the maximum relative deviation and the standard deviation are less than 3.0% and 2.7%, respectively. For the single-sensor pyrheliometer, the corresponding deviations are 3.18 and 1.5%, respectively. The instruments are simple and inexpensive. Their accuracy can meet the need of routine measurements of solar irradiance.