A thermal pulser utilizing I2R heating was developed for phase transformation studies in metals. The pulser combines fast rise and fall times and a feedback controlled, flat topped temperature pulse. The temperature sensor is either a three‐legged thermocouple arranged to cancel out IR drops due to current in the sample, or a radiation thermometer. Sample and thermocouple fatigue life were materially improved by employment of a sample mounting arrangement which combined prestretched spring clamps to eliminate sample bowing and a symmetrical design to essentially eliminate transverse magnetic forces on the sample. Measurements show peak temperature of consecutive pulses repeatable to approximately ±1%, and temperature during a pulse from 0.1 to 10 sec in duration constant to approximately ±0.7–1.5%, even for metals with high thermal conductivity. The power capability is adequate to melt thin samples of most metals.