I want to apply a pulse-echo methodology (by using one single transducer as both transmitter and receiver). Do you know how to connect the transducer to the wave generator and oscilloscope to detect both transmitted pulse and echoes?
I have been trying to use the burst feature in manual mode by pressing the trigger button in the wave generator. However, when I do that, the oscilloscope is only capable of reading the wave generated instead of receiving as well the back-wall echo.
I am also using these types of transducers from Stemininc: Piezo Ceramic Plate 20x15x2.1mm 1 MHz, Piezo Ceramic Plate 7x7x0.2mm 250 KHz, and Piezo Ceramic Plate 20x15x3mm 710 KHz. Thus, I'm not sure if they are indicated to use this pulse-echo methodology.
I have two alligator cables connected to the oscillator and to the transducer: 1 to work as the transmitter and one to work as the receiver; and they are both connected in the same wires of the transducer. However, so far, it seems that these alligator cables connected to the same transducer are giving me the same wave.
Do you know if this equipment as it is is capable of doing these readings:
- reading of the transmitted and received waves (of amplitude vs. time), separately, by using this setup as is (when using two different cables), or
- reading of the transmitted and received waves combined in the same curve: maximum peak sent and resultant received echoes (back-end wall or cracks, for example)?
I am using a manually triggered pulse sine wave of amplitudes of either 10Vpp or 24Vpp, but the outcome is always identical. Should I be using a higher amplitude to make sure I receive the echoes?
Any help would be much appreciated.
Hello Catarina Baptista-Pereira ,
You basically need a T/R (Transmit/Receive) switch between your signal generator and your transducer, and your oscilloscope and your transducer. When your signal generator is producing the outgoing periodic pulses (or gated trains of sine waves) used to drive your transducer, the T/R switch disconnects the oscilloscope from the transducer. While your transducer is receiving the reflected signal between the periodically generated pulses from the signal generator, the T/R switch connects the oscilloscope to the transducer, but disconnects the signal generator from the transducer. Note, be aware of the concept of range ambiguity, i.e., if the reflecting surface is further away than the round trip time between two of the signal generator's pulses, then the incoming reflected signal may fall between the next two pulses of the signal generator making the reflecting surface's distance appear shorter than it actually is.
How you actually realize your T/R switch will depend on your drive signal amplitude, and the input impedance of your oscilloscope.
Regards,
Tom Cuff
Dear Thomas Cuff,
Thank you for your reply. I was not aware of this extra piece of equipment (T/R switch) and I have been searching about it. It was very helpful the information you shared.
Catarina Baptista-Pereira
I would also suggest that you include some form of compressor/expander (often accomplished with a crossed diode pair) to isolate the sensitive input amplifier on your oscilloscope from the high amplitude drive signal. Realistically though, the most convenient way to accomplish this, and the T/R switching that Tohmoas mentions is to use an off-the-shelf pulser/receiver. We frequently use the DPR range from JSR ultrasonics (www.imaginant.com) in our own work.
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