PGA460-Q1: Getting different distance below and beyond operating range

Hello Adam,

Thanks for posting the sensors forum! The 1124cm reading indicates that no object was detected. Whenever the UMR is read from the PGA460-Q1 if an object is not detected the results will give maxed out readings so the data will indicate 0xFFFF for the MSB+LSB for the ToF, 0xFF for the peak, and 0xFF for the peak amplitude of the echo. So you could update your algorithm to toss our readings that are not detected by looking for these factors.

If you are trying to identify items farther than 3 meters make sure that your excitation voltage is capable of reaching further than the 3m and you may require to update your threshold/gain configurations to adjust for the further distances.

Readings smaller than 30cm can be difficult if you are running a single device with a single transducer. This is mainly due to a limitation in ultrasonic sensing in general. When you send out a signal through a transducer the excitation voltage saturates the transducer which also serves as your method of detecting returned echoes, but since that transducer is saturated with voltage you must wait for the voltage to decay enough to allow for signals to return back to the transducer. The minimum distance when using a single transducer is mostly dependent on the excitation voltage, transducer frequency, and amount of pulses being emitted from the device. If you find that your voltage reduces before the 30cm mark it may be possible that your threshold configuration may not be at the optimal spot and reducing this may be necessary. If you are using multiple devices and transducers then the minimum distance achievable should essentially be near 0.

If you have not used the PGA460-Q1 EVM and GUI I typically suggest to try and use this as this provides a visual representation on the timing/levels that are configured on the device (gain and threshold configurations). I hope this helps please let me know if there are further questions I can help out with!

Best,

Isaac

Thank you for such prompt support. Could you recommend any strategies for filtering signals in firmware to determine if our ultrasonic transducer is functioning effectively at distances under 30cm?

Hello Adam,

No worries, always glad to help out. As far as implementing any filtering on the firmware side for distance below 30cm, this may not be really possible since as I mentioned the issue here is that the sensor is saturated hence any signals that come in are not really perceived and the frequencies are all the same so filtering out frequencies is not much of an option. There are some changes you could do to hardware to reduce the ringing time in to improve the detection under 30cm: https://www.ti.com/lit/an/slaa732a/slaa732a.pdf

Other users have also placed their sensor inside recessed portions of their system to help artificially reduce the blind zone distance, but the main way to eliminate the minimum distance detection is by using more than one transducer.

Best,

Isaac