In Transformer Driven Mode, The Secondary Voltage Appears As A Distorted Sinusoidal Waveform; How Do I Clean-Up My Driver Signal Exciting The Transducer; I Can Hear An Audible Clicking Sound From The Ultrasonic Sensor. Is This Normal; How Can I Determine The Characteristics Of My Transducer If No Datasheet Is Provided, Or I Do Not - Texas Instruments PGA460 Troubleshooting Manual

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example of how much of an impact frequency can have on peak performance.
• Four Layer Board Option
– Additional groundling layers will help with noise rejection on the board level.
• Motor Switching Frequency
– Because the most influential factor is the motor switching frequency, increasing the motor
frequency to be at least 8 kHz beyond the nominal center frequency of the transducer will prevent
the PGA460 noise floor from saturating. If the switching frequency is greater than the resonant
frequency, there is no likelihood that harmonics will interfere with the transducer performance.
• Conductive Shielding
– Use conductive shielding to ground and surround the ultrasonic enclosure such that the noise is
absorbed by the shielding, rather than coupling onto the board, cables, transformer, or transducer
of the ultrasonic module.
• Alternative Transducer
– Use conductive shielding to ground and surround the ultrasonic enclosure such that the noise is
absorbed by the shielding, rather than coupling onto the board, cables, transformer, or transducer
of the ultrasonic module.
6.4 In transformer driven mode, the secondary voltage appears as a distorted sinusoidal
waveform. How do I clean-up my driver signal exciting the transducer?
The most influential variables responsible for forming the sinusoidal driver at the transducer are the
external tuning capacitor and damping resistor values. See the
and Software Optimization
also impact driver cleanliness. If the transformer is saturated through the primary windings, then distortion
will be present at the peaks of the waveform. Reduce the current limit until the peak is no longer distorted,
but still maximized in peak-to-peak amplitude. Though a clean driver is ideal, more sound pressure level is
still be generated from a larger peak-to-peak distorted sinusoidal waveform. Ensure the current limit is
enabled in transformer driven mode.
6.5

I can hear an audible clicking sound from the ultrasonic sensor. Is this normal?

An audible clicking noise may be heard when driving the transducer, especially in the transformer driven
mode. This typically indicates that the sensor is being driven at the maximum supported power, but can
also indicate that the sensor is being overdriven. As long as the current limit is applied, the transformer
saturation current is not exceeded, the transducer driving voltage specification is not exceeded, and the
pulse count is limited, there is no reason to be concerned. The noise is mainly an artifact of the excitation
mechanics of the transducer.
6.6 How can I determine the characteristics of my transducer if no datasheet is provided,
SLAA733 – May 2017
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application report for details on selecting these values. The current limit can
120
Limit Disabled
100
80
60
40
20
0
-20
-40
-60
-80
-100
-120
0 5 10 15
Figure 29. Transducer Driver Waveform Smoothness
PGA460 Frequently Asked Questions (FAQ) and EVM Troubleshooting
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Running the Hardware and Environmental Factors
PGA460-Q1 Ultrasonic Module Hardware
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