0
\$\begingroup\$

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.

\$\endgroup\$
7
  • \$\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
    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
    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
    Dec 26, 2017 at 22:08
  • \$\begingroup\$ @Barry It is through skin, I am using the hydrogel that you get from hospitals. \$\endgroup\$
    – user172904
    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
    Dec 27, 2017 at 3:20

1 Answer 1

0
\$\begingroup\$

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.

\$\endgroup\$
3
  • \$\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
    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\$ 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
    Jan 3, 2018 at 18:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.