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Original question:

PGA450-Q1: low temperatures causes no response from sensor

PGA450-Q1: echo changes

GUY WAISMAN
Prodigy 70 points
Part Number: PGA450-Q1

Hi,

we've been reported by our customers that some of our unit's distance measurements are off.

investigation of the fifo data, shows that the echo amplitude is much higher and saturation time is much longer when temperature is lower. if you look at a cycle of 24 hours - this happens mostly during the night.

xlsx examples are attached. 

you can clearly see longer saturation that crosses our defined thresholds in comparison to the 15:00 example where saturation time cuts in half,

notice that we do some filtering of the first 80 samples so that is why the begging of the fifo is distorted from the original fifo (outcome is still the same).

am I suppose to use less pulses during the night? in clod temperatures? 

can you explain what causes this effect?BinId - 2375 _(4)_LogFile_26.02.22_15.xlsxBinId - 2375 _(1)_LogFile_27.02.22_22.xlsxBinId - 2375 _(2)_LogFile_27.02.22_15.xlsxBinId - 2375 _(3)_LogFile_26.02.22_22.xlsx

thanks,

guy

  • 0
    TI__Mastermind 23045 points

    Hello Guy,

    Thanks for posting to the PS forum. I reviewed the data provided although I was not sure which data log belong to cold and hot temperatures, I assumed the data that looks like the image below belonged to the cold temperatures. So please let me know if this assumption is correct.

    One thing to note is that the speed of sound is dependent on the ambient temperature. When the temperature is high molecules are much easier to get excited and the speed of sound is actually faster in comparison to cold temperatures. It is possible that this could be what is occurring in this instance. Another though would be to verify the operating temperature of the transducer and see if the transducer is also cooled if it also affects its performance. Since the transducer physically vibrates I would assume it is also subject to perhaps ring slower than the intended frequency, lower frequencies translate to longer ringing/decay times.

    Reducing the amount of pulses would definitely reduce the ringing time. I hope this helps and feel free to let me know if you have any other questions.

    Best,

    Isaac