Abstract: In a measuring instrument for obtaining information about a medium through which ultrasonic signals can be transmitted or from which ultrasonic signals can be reflected, transducers (21 and 22) are provided for sending and receiving the ultrasonic signals. Electronic amplification means (25) is provided to amplify received ultrasonic signals to a level suitable for processing by a signal processor (23) to provide the desired information. A power supply (20) is provided for activating the sending and receiving transducers (21 and 22) and the amplification means (25). Strobe switching means (26) is provided for activating the power supply (20) during periodic intervals, leaving intervening spans of time when the power supply (20) is inactive. Capacitive means (32) is provided for activating the amplification means (25) when the power supply (20) is inactive,thereby precluding electronic noise generated by the power supply (20) from establishing a gain limit for the amplification means (25).