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AD5933 for impedance monitoring but maybe reaction exists

Question asked by xliu44@utk.edu on Jul 24, 2012
Latest reply on Jul 26, 2012 by xliu44@utk.edu

Hi all,

 

We are using the AD5933 for fast disease diagnosis (http://www.gizmag.com/portable-device-instantly-detects-diseases/21672/), but after I compared the results acquired using ad5933 with the ones by Impedance Analyzer (Agilent 4294a), I found they were different. So I am thinking maybe there was reaction caused by DC component in the process.

 

The paper from AD (http://www.analog.com/library/analogDialogue/archives/42-08/blood_coagulation.pdf) presented one ac coupled circuit, but I would like to know if my design will work first, because I have engraved the traces already.

 

Simply put, I added the Vout of AD5933 with a variable DC from an MCU using AD8641, this sum was connected to a switch/MUX while the Vin of AD5933 was also connected to this switch. After the voltage was stable (~ms), the switch will open and the samples will be stimulated by the voltage (Please take a look at the schematic). Will this work? Thank you so much!

 

And I also have some questions:

I will power the whole system through USB port (from a computer or a battery), is the power stable according to your experiences?

I am designing a multi-channel edition of this one, and I chose AD5932 as a signal generator instead of AD5933 (in the single channel one, the AD5933 acts as both signal generator and impedance analyzer). Will similar circuit suit for AD5932? The reaseon I use AD5932 is that it is cheaper and I observed that the waveform from AD5932 is tidier than AD5933.

 

Thank you so much for this, I deeply appreciate your help.

Xiaozhu

 

消息编辑者为:Xiaozhu Liu

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