A pulse controller device for controlling the excitation of a heat source used in thermographic imaging is disclosed. The pulse controller device comprises a power supply, a heat source coupled to the power supply, a device coupled to the power supply signaling the power supply to deliver electrical power to the heat source, a sensor for sensing the delivery of electrical power to the heat source, a flash duration module coupled to said sensor for measuring a duration of time, and a gate device coupled to said flash duration module for gating the electrical power utilized by the heat source. A method for thermographically evaluating a sample is also disclosed.