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I am currently messing around with a project I thought would be fun but am having some issues.

My goal is to use a signal generator to send a wave through my 7MHz (Steminc) piezo s-configuration transducer (through the carotid artery) and to use another transducer to capture the scattered wave and measure the doppler shift. I am trying to do a proof of concept first, and want to just get the measurement through a scope; however, when I try placing them, I only get noise.

My electronics background in theory is ok, but in practice is not strong at all. I'm assuming I need some circuitry or have overlooked something along those lines. I was hoping someone could give me some guidance, whether it be a useful resource or somewhere to start as far as the circuitry.

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  • \$\begingroup\$ We could sure use a schematic or diagram of some type. We need to see what you are doing. You may need an amplifier specific to the transducer your using. \$\endgroup\$
    – user105652
    Commented Dec 26, 2017 at 19:48
  • \$\begingroup\$ Are you trying to do this in air? If so, it is likely that the transducers need to be in a liquid for better coupling efficiency. \$\endgroup\$
    – Barry
    Commented Dec 26, 2017 at 22:07
  • \$\begingroup\$ Signal from a signal generator is most probably ways too low to effectively drive transmitting transducer.... usually a few 10 Vpp is needed, can your generator reach ? \$\endgroup\$
    – carloc
    Commented Dec 26, 2017 at 22:08
  • \$\begingroup\$ @Barry It is through skin, I am using the hydrogel that you get from hospitals. \$\endgroup\$
    – user172904
    Commented Dec 27, 2017 at 3:19
  • \$\begingroup\$ @Sparky the link for my transducer steminc.com/PZT/en/piezo-ceramic-transducer-16x025mm-s-7-mhz I'm sure that's not what you're looking for but I don't have much else. \$\endgroup\$
    – user172904
    Commented Dec 27, 2017 at 3:20

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Signal level directly from the transducer is probably tens of mV at most, and may be getting lost in the scope noise. Try to reflect or transmit from only a few mm and (if not already doing so) use your scope probe in X1 mode, which reduces the input-referred noise floor by an order of magnitude.

For more serious work you will need an appropriate preamplifier.

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  • \$\begingroup\$ The signal generator is pushing a sine wave at 10Vpp, my transmitter is basically right next to my reciever. These are single element transducers, the issue could be that I am placing the transducers at almost 90 degress... do I need anything to be connected to the receiving transducer as far as amplifiers, etc? \$\endgroup\$
    – user172904
    Commented Dec 27, 2017 at 3:25
  • \$\begingroup\$ Any specs on the transducers? Are they coupled through an appropriate medium for their design (reasonably acoustically impedance matched)? \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Dec 27, 2017 at 4:28
  • \$\begingroup\$ It may be me but I do not think the site gives much, for example I cannot figure out what voltage the transducers should ideally be driven at (see link). They have a material spec sheet (see link), for material SM211. They are being coupled with a hydro gel, like one you would get at the doctors. I do not currently have a matching material implemented. \$\endgroup\$
    – user172904
    Commented Jan 3, 2018 at 18:40

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