TUSS4440: Maximum Measuring Range

Hi Mark,

The sensing distance is dependent on several factors.

A) Drive voltage 

Drive voltage impacts the energy required to drive the transducer at resonance and stronger the drive voltage the higher the SPL and larger the amplitude it can drive the transducer. If the wave has to propagate through a thick material a stronger drive voltage is needed it may be that a boost is required to generate high voltage. 

B) Frequency of the transducer

Frequency of the transducer also limits the sensing distance. Lower frequency is used to measure longer distance and higher frequency is used to measure shorter distance. This is based on the physics, the higher frequency as it hit the object the return echo signal may not have enough energy to transition back into the AFE. 

C) Medium like Air, water

The region of operation also impacts as ToF flight is dependent on sounds waves the sound waves travel different in Air vs water. 

To answer your question on the sensing range as it completely depends on the system we need more information on the system. To begin I would point you to the content on Basics of Ultrasonics that explain the principles. This will help explain some of the concepts and also limitations as discussed. 

The datasheet Application section also provides guidance on the Voltage and frequency of transducers and the distance range. 40Khz can measure 6m whereas 400Khz can measure 300mm. Let me know if this helps. 

Hi Tony,

The record length is dependent on the time the device spends listening for ultrasonic reflections from target objects. With the TUSS4440, the listen mode is the default mode. At the end of a burst, the device enters listen mode and stays in this mode until the next time the user triggers a burst event. Since the device stays in listen mode until the next time the user triggers the next burst, the user can control the record length.

However, since the TUSS4440’s analog output may have to be sampled by an external ADC and microcontroller, other system parameters can affect the record length. Some of these parameters include memory space available for storing samples and the ADC sample rate.  With the microcontroller settings used for the TUSS4440 GUI, a maximum record length of 72 ms is supported, which corresponds to a maximum distance of 12.3 m if we are assuming a speed of sound value of 343 m/s. If you were to store more samples, you should be able to theoretically sense further distances, assuming that the received ultrasonic reflections are strong enough to be sensed.

Regards,

Mekre