A noncontact temperature sensing device receives radiative emissions from a sensed object to measure radiant heat flux and computes a temperature using multiple photodiode sensors, or elements, each sensitive to a different bandwidth of near IR light. The device samples a fluctuating heat source such as a flame or explosion at a fast sampling frequency, and compares corresponding or simultaneous readings in each bandwidth for computing a ratio of the respective bands and determining a temperature via ratio pyrometry. Multiple sensors of adjacent bands each receive corresponding readings of near IR emissions, perform fast, concurrent sampling to mitigate inconsistencies of heat source fluctuations, and compute a temperature based on a ratio between the sampled readings of the different bands. Near IR detection allows common and inexpensive photodiodes to be employed, and the photoelectric rather than thermoelectric sensing allows faster sampling and at a greater distance from the sensed heat source.