Coherent signal detection techniques are applied to conventional ultrasonic pulse‐echo measuring apparatus to achieve a 20–25 dB improvement in the minimum useful signal. Logic circuitry is described which generates all the reference and trigger waveforms required by the sampling oscilloscope, lock‐in amplifier, and other equipment. No other pulse generators are required. Amplitude adjustment of the pulsed rf comparator is determined to be equal that of the echo by a null indication of the lock‐in voltmeter.