The minimum detection range of ultrasonic systems is determined by the properties of the transducer itself and the way it is pulsed. The blindspot, or transducer ringing-decay time, is caused by the resonant energy oscillating at the base of the transducer in a monostatic configuration (that is, one that both transmits and receives). Higher frequency transducers have smaller ringing-decay times, thus reducing the minimum range. Using this approach, however, will reduce the sensing range. Using a bistatic approach can eliminate this ringing behavior, as this setup isolates the sending and receiving transducers, but it will be double the cost of a monostatic solution.

Another way to reduce the blindspot is by lowering the pulse count and lowering the current limit. This may reduce the strength of the echo that is returned, however.

If a low-frequency, monostatic setup must be used, and if lowering the pulse count and current limit decrease the integrity of the received echo, additional passive components may be introduced to reduce the blindspot. A damping resistor in the range of 500 Ω to 25 kΩ may be added in parallel to the transducer to reduce the ringing-decay time.

For more information on how to optimize the ultrasonic setup, see the PGA460 Ultrasonic Module Hardware and Software Optimization application report (SLAA732).