Can a Simple AD Converter Be Built for Ultrasound Analysis?

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Discussion Overview

The discussion revolves around the feasibility of building a simple analog-to-digital (AD) converter for analyzing ultrasound signals, specifically in the context of a bat detector project. Participants explore various approaches, including standalone ADCs, microcontrollers with built-in ADCs, and the potential use of existing USB devices or sound cards.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that a chip exists for the desired AD conversion, but questions whether it should sample at 200 kHz instead of 196 kHz.
  • Another participant proposes using a microcontroller with a built-in ADC, specifically recommending the PIC 32 bit series for its sampling capabilities and USB support.
  • Concerns are raised about the complexity of programming a PIC microcontroller, especially for beginners, with a request for recommendations for ready-to-use ADCs.
  • Some participants mention that ordinary sound cards may sample up to 200 kHz, with one suggesting the modification of a sound card to achieve higher sampling rates, although uncertainty exists about the necessary software and hardware modifications.
  • A participant recommends a ready-made USB oscilloscope, noting its sufficient bandwidth and sampling rate for the intended application.
  • Discussion includes the possibility of modifying sound cards to remove built-in low pass filters, with questions about the feasibility of such modifications.
  • Pro audio sound cards are mentioned as capable of sampling at higher rates (192 kHz or 384 kHz), with a specific model cited as an example.

Areas of Agreement / Disagreement

Participants express various viewpoints on the best approach to achieve the desired AD conversion, with no consensus on a single solution. Multiple competing methods, including standalone ADCs, microcontrollers, and sound cards, are discussed without resolution.

Contextual Notes

Participants note limitations regarding the programming complexity of microcontrollers and the potential need for modifications to sound cards, which may depend on specific hardware configurations and software capabilities.

DrDu
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I was building a simple bat detector for a child and also built one for me:
http://home.earthlink.net/~bat-detector/SBD2Parts.html
Now I was wondering whether it would be possible to built a simple AD converter,
which can be fed the amplified signal of the microphone before it enters the counter,
so that the signal can be analyzed on the computer.
Does anybody has an idea how to realize a cheap AD converter for that purpose?
It should sample at at least 196 kHz to be able to resolve up to 100 kHz signals.
Maybe there exist also ready to use USB devices for that purpose?
 
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DrDu said:
I was building a simple bat detector for a child and also built one for me:
http://home.earthlink.net/~bat-detector/SBD2Parts.html
Now I was wondering whether it would be possible to built a simple AD converter,
which can be fed the amplified signal of the microphone before it enters the counter,
so that the signal can be analyzed on the computer.
Does anybody has an idea how to realize a cheap AD converter for that purpose?

It seems likely that there's a chip that does what you want:
http://www.analog.com/en/analog-to-digital-converters/ad-converters/products/index.html

DrDu said:
It should sample at at least 196 kHz to be able to resolve up to 100 kHz signals.

Would it not then have to sample at >= 200 kHz?
 
A standalone ADC will need lots of additional circuitry to make it work. But instead, a micro-controller could be used which already has a built in ADC. I'd recommend a model with a bit of a punch such as the PIC 32 bit series. They come with ADCs that can do 1 MSPS sampling, and support USB.
 
what said:
A standalone ADC will need lots of additional circuitry to make it work. But instead, a micro-controller could be used which already has a built in ADC. I'd recommend a model with a bit of a punch such as the PIC 32 bit series. They come with ADCs that can do 1 MSPS sampling, and support USB.
The microcontroler solution sounds interesting, however, from what I found in the web, the programming of a PIC is not trivial, and I am quite an electronics beginner. I had hoped that someone might recommend me a ready to use ADC. I also found some links which I interpreted as claiming that even some ordinary sound cards can sample up to about 200 kHz.
 
DrDu said:
The microcontroler solution sounds interesting, however, from what I found in the web, the programming of a PIC is not trivial, and I am quite an electronics beginner. I had hoped that someone might recommend me a ready to use ADC. I also found some links which I interpreted as claiming that even some ordinary sound cards can sample up to about 200 kHz.

From the sound of the OP, I thought you wanted to build an ADC to PC interface.

One can also get a ready made USB scope such as the pico-scope:

http://www.picotech.com/picoscope2000.html

The cheapest models have about 10 MHz bandwidth and 50 MSPS which should be more than ample to sample a 200 KHz signal.

Edit: I guess you could also mod a sound card, they might have high sample rates. But I'm uncertain about the software needed to push it to maximum, and hardware mod to make it work. I assume sound cards have audio filters which you would have to remove.
 
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Thank you, I think I shall opt for an oscilloscope. When I was last playing with electronics (about 20 years ago), a
storage oscilloscope was prohibitively expensive. Is picoscope recommendable?
Nevertheless I would like to know whether it is possible to modify an ordinary sound card.
As I understand, the sampling rate would be sufficient, however, they have a built in low pass filter. Do you think it is possible to knock out the low pass filter?
 
There are "pro audio" soundcards (meant for computer music creation, not game playing) that sample at 192 kHz or even 384 kHz. For example http://www.m-audio.com/products/en_us/Audiophile192.html

That card has more options than you need, but it's a fairly old design now and you should be able to buy one for about $100 to $150.

The "built in" sound chipsets in most consumer-level PCs only run at the sample rate of CDs, i.e. 44.1KHz (or sometimes 48kHz) and you can't do any simple mods to change that.
 
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