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Referenced Potential Multiplexing

rahman yunus
Prodigy 130 points

Hi,

I have a circuit design with 16 electrodes. One electrode pair is used for current excitation (10mA) while the remaining are used for potential measurements (PM). The frequency varies from 1kH to 500kHz. However for PM it requires reference potential which is adjacent of the excitation pair. The maximum potential difference between electrodes is 2.5V.

My problem is multiplexing the reference potential as the value occurs at all terminals nIN- (n=1,2,3...16) simultaneously. I come up with the schematic and would like to know if the output from MPC506AU which I connected is correct. For simplicity I only show the first 2 out of 16 connections which are (1IN- and 2IN-). Any suggestion or advice is much appreciated.

Regards

Fazlul

8270.Front end multiplexer switching.pdf

  • 0
    TI__Genius 9860 points

    Hi Fazlul,

    If the value occuring at all terminals simultaneously is a problem, try reversing your input and outputs of the MPC506AU. It looks like you have all of the amplifiers connected to the common port (OUT). If you attach the 0.05Vpk to the OUT and use the multiplexer to determine which amplifier receives the output. As the switch turns into a resistor when turned on, it is bidirectional.

    Is there any reason you are connecting all of the outputs to the single OUT pin?

    -Ryan

  • 0 in reply to C. Ryan Land
    Prodigy 130 points

    Hi Ryan,

    I'm working on project which requires me to obtain surface potential from 16 electrodes attached on a pipeline. In order to obtain the measurements from the electrodes, a pair of electrode is injected with ac current (10-20mA) at frequency between 50kHz-500kHz. The surface potential from the remaining electrodes are measured. The process is repeated for next electrode until to electrode 16. My problem is on each surface potential (V2,V3,...V16) it will referred to reference electrode which is adjacent to the excitation pair electrode. It also means the referenced electrode changes during the process. I trying to make the surface measurements as fast as possible and I am thinking the referenced potential appears at the input of 16 instrumentation amplifiers simultaneously. Now I am confused on how to make this happened. Please help.

    Regards

    Fazlul