Ultra Low Budget 50khz data acquisition
Ultra Low Budget 50khz data acquisition
(OP)
Hello. If you are in a rush, skip to the bold text.
I am currently working on a project using an arduino Uno R3 micro controller for data acquisition. This is outside of expertise (As if I have one of those). The Scope of this project is not for high precision. This is a monitoring system which will not have the responsibility of high precision. What I'm monitoring is engine knock. I am sampling well above the Nyquist rate for engine knock, and the samples are 10 bits. It is sufficient for the intents and purposes of the project, but don't be afraid to point out the more optimal routes than an Arduino Uno.
Background/Current status.
- I have figured out how to over-clock the arduino to acheive 50khz sample rate at 10 bits (500,000 bit/sec).
- I am able to sustainably transfer the data bytes to my PC by sending them in 1kb batches
- I have a non-resonant piezoelectric knock sensor with a shielded wire (Bosch 0 261 231 047).
- The charge from the knock sensor is of very high impedance (near 1 Mohm), and presumably low in voltage
- The ADC on the Arduino requires impedance less than 10,000 ohms (zero is ideal)
- The voltage range of inputs should ideally be between 0 and 5 volts.
Questions/Next steps.
- For this application, whats the easiest way to amplify this signal into a low impedance 0-5v charge?
- Is there anything inexpensive that I could buy off the shelf to do this?
If this thread has interest, I will expand the purpose of this thread to help other beginners do similar projects later.
Thank you
I am currently working on a project using an arduino Uno R3 micro controller for data acquisition. This is outside of expertise (As if I have one of those). The Scope of this project is not for high precision. This is a monitoring system which will not have the responsibility of high precision. What I'm monitoring is engine knock. I am sampling well above the Nyquist rate for engine knock, and the samples are 10 bits. It is sufficient for the intents and purposes of the project, but don't be afraid to point out the more optimal routes than an Arduino Uno.
Background/Current status.
- I have figured out how to over-clock the arduino to acheive 50khz sample rate at 10 bits (500,000 bit/sec).
- I am able to sustainably transfer the data bytes to my PC by sending them in 1kb batches
- I have a non-resonant piezoelectric knock sensor with a shielded wire (Bosch 0 261 231 047).
- The charge from the knock sensor is of very high impedance (near 1 Mohm), and presumably low in voltage
- The ADC on the Arduino requires impedance less than 10,000 ohms (zero is ideal)
- The voltage range of inputs should ideally be between 0 and 5 volts.
Questions/Next steps.
- For this application, whats the easiest way to amplify this signal into a low impedance 0-5v charge?
- Is there anything inexpensive that I could buy off the shelf to do this?
If this thread has interest, I will expand the purpose of this thread to help other beginners do similar projects later.
Thank you





RE: Ultra Low Budget 50khz data acquisition
TTFN
I can do absolutely anything. I'm an expert!
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RE: Ultra Low Budget 50khz data acquisition
To minimize trouble-shooting while developing/testing this, could I possibly purchase the desired an op-amp from an online store? I want a solid one for getting a baseline.
http://www.rhinopower.org/knock/knock.html
RE: Ultra Low Budget 50khz data acquisition
TTFN
I can do absolutely anything. I'm an expert!
homework forum: //www.engineering.com/AskForum/aff/32.aspx
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers
RE: Ultra Low Budget 50khz data acquisition
This is an amp they offer: http://www.analog.com/media/en/technical-documenta...
It is the most optimal setup that I have seen so far. Thanks for the help, I am probably going to buy their evaluation board.
RE: Ultra Low Budget 50khz data acquisition
I am hoping that the AD8220 amp will be able to amplify the signal up to a maximum of 5 volts.
The sensor that is providing signal is: http://www.bosch-motorsport.com/media/catalog_reso...
The data sheet is very high level, but the output impedance is actually around 500K ohms.
Can anybody foresee any of the problems that I will face when amplifying signal with those two products acting as a system?
The knock sensor is shielded relatively well, and I am going to be processing the data digitally. The software I will use is Matplotlib, or I may be able to use Matlab.
After I get it working, I hope to integrate a circular buffer for the data. This is for monitoring transients, so I don't really need every single data point to be logged.
"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin
RE: Ultra Low Budget 50khz data acquisition
The Bosch sensor appears to be a bare piezo-crystal that would typically need a charge amplifier. Can your amplifier convert charge to voltage before amplification?
Walt
RE: Ultra Low Budget 50khz data acquisition
I am not sure that the AD8220 can convert charge to voltage, but I am somewhat doubting it. The sensor produces 26 ± 8 mV/g at 5khz. Id definitely like to understand this more if you could help.
This is the information that I was basing my theory on:
(Using the same sensor that I have) The sensor output was fed directly into the analyser (high impedance) to avoid loading the sensor andtThe analyser was set up to perform a frequency sweep at 1g between 1kHz and 25kHz. The result is shown below:
http://www.rhinopower.org/knock/knock.html
RE: Ultra Low Budget 50khz data acquisition
Google Search: charge amplifier versus voltage amplifier
http://www.ti.com/lit/an/sloa033a/sloa033a.pdf
https://www.endevco.com/resources/expertArchive/Ap...
http://www.mkesc.co.uk/Chargeamps.pdf
http://www.mmf.de/instrumentation.htm
Walt
RE: Ultra Low Budget 50khz data acquisition
I do know that my amp has a FET buffer in the input. The output impedance from the sensor is 500kOhms, the input impedance on the amp is 10Mohms, if I remember correctly. I have some reading to do on the amps I have, and alternative plans of action.
RE: Ultra Low Budget 50khz data acquisition