How It Works: Trusted Technology, Made Simple The TempoTherm uses infrared technology to measure the heat emitted from the temporal artery, a major blood vessel just beneath the skin of the forehead. With a gentle touch and smooth scan across the forehead, the thermometer captures up to 1,000 readings per second, selecting the most accurate one using Exergen’s patented Arterial Heat Balance system. When to Call the Doctor: Start with TempoTherm When to seek medical advice?