External ADC for scientific application (HPLC)

[system]

Hello, I'm a forum's worst nightmare; I'm a n00b to microprocessors, a biochemist, a medical student and researcher, only hobby programmer (C++ & Java) with a CS minor, and of course I have lots of clueless questions!

Research budgets can often be ridiculously small and we're trying to develop an Arduino datalogger solution for reading sensor data from some of our equipment. We've previously used LabView and a DAQ with success but are looking for a more customizable application we can use cheaply on more systems. We're doing high performance liquid chromatography (HPLC) for biologic samples if that matters. We plan on publishing and open-sourcing any successful results.

So, the HPLC machines work well and produce a signal from a cathode/anode sensor, a UV sensor or the like. Detecting and recording this signal with an Arduino is the goal of our current project. Sadly the Arduino's 10 bit resolution ADC is probably insufficient and I'm interested in an external ADC. Boy, did I take too long explaining that?

I'm looking at an Arduino Uno with prototyping board and various ADCs:

• MCP3422: http://forums.adafruit.com/viewtopic.php?f=31&t=12269
• LTC2485: http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1155,C1001,C1152,P13712
• ADS8332: focus.ti.com/docs/prod/folders/print/ads8332.html
• ADS8344: ADS8344 data sheet, product information and support | TI.com
  We're interested in >=16 bit resolution and 100SPS would be really nice. Bigger is better of course. Are there any thoughts on this or perhaps tutorials or blogs that I missed in my research? Perhaps I'm wrong looking at Arduino but it certainly seems like a powerful platform and I'm interested in some of the scientific work that I've seen exploring it's possibilities (for example: phys.csuchico.edu/~eayars/publications/Arduino-datalogger.pdf)

Also, I'm sure I'll eventually be bugging the software interface forums as I write into our existing Java based software new code to interface with the datalogging Arduino. By the way, we're looking at transferring the data with a USB port and using USB/wall power so data storage and battery life will hopefully not be issues.

Thank you for you consideration,
/me

[system]

There is certainly no shortage of A/D converters available for what you want to do. If you want greater resolution than 10 bits you are probably also interested in a low-noise high-precision acquisition. Beyond just the number of bits in the A/D you have to consider how quiet the analog signal path is to the A/D and how accurate the A/D's voltage reference is. This is the old precision vs. accuracy issue

You also need to consider the output impedance of your sensors and the input impedance of the A/D. For example, the Arduino's AVR processor recommends an sensor output impedance of no more than 10 kOhms. Any greater and input signal buffering is recommended (I'd recommend that anyways).

I guess what I'm saying is that if signal quality and accuracy are important, your final result probably shouldn't live on a breadboard.

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