Methods of flame detection are investigated using a pulsed detonation combustor as a research platform. An experimental pulsed detonation combustor using ethylene and propane fuel with an operational frequency up to 11 Hz has been assembled without the use of mechanical valves. A highly instrumented acrylic tube is used to experimentally examine and visually observe the deflagration to detonation transition region during cyclic operation. In this experimental setup, high frequency pressure transducers, ionization probes, CCD cameras, and flame sensing photo-diodes are used to simultaneously determine how the pressure rise, chemiluminescent flame front, and ionization of the gaseous mixture are interrelated and coupled near this transition point. The reaction of both photo diodes and ion probes to the passage of a flame front is nearly identical; the flame front location is confirmed with high speed video and occurs when the signals of each instrument begin to rise from a ground state. The induction delay between the passage of the pressure wave and the passage of the chemiluminescent combustion wave is directly observed by comparing engine pressure as recorded by dynamic transducers to ionization as recorded by ionization probes and photo diodes. Multiple peak ionization zones are observed during a single detonation cycle, indicating the presence of retonation waves, expansion fans and reflected wave characteristics after the initial detonation wave exhausts from the engine; these observations are supported by coincident pressure rises and visual observations. Advantages and disadvantages of each flame detection method are compared.