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Want a multiplexer and demultiplexer for my problem occured.

Prodigy 110 points

Replies: 4

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Respected Sir / Madam,

I am doing a university project on a topic structural damage location (x,y) on a thin aluminium plate (1m x 1m). There are 4 piezoelectric transducer situated at 4 corners of my plate. I am using a surface guided wave which has amplitude of +7 V and -7 V and frequency of 500 Khz. I am using THS3091 ic which successfully excite the piezo one at a time. My task is to excite 4 piezo at different time (for 2 us) and sense the wave from the same 4 piezo as soon as excitation gets complete for 1 sec ie to take 16 sensing reading. So for this i have used CD4052 as a multiplexer and demultiplexer for switching 4 piezos. As it switching time is 20 nsec (less than 1 usec).

  

In the above figure, S1 is the common pin and there are 4 different but same circuit which give output. My actual problem is the Csd capacitor placed parallel to switch. When the switch is off position still my wave passes through the Csd capacitor of low amplitude. For solving my problem during excitation, I used RL=10k ohm and CL=1nF. which in turn reduced the effect of Csd capacitor ; But during sensing, all 4 piezo start sensing at same time. Each piezo will sense different wave which had been reflected from boundary. The wave have variable amplitude ranging from 0 mV to (+100 mV and -100 mV). My intention is to sense wave from one piezo at a time and store in a micro-controller memory. For this I set one switch in on position and 3 switch in off position of CD4052. But in actual, from the Csd capacitor of 3 off switches transferring the sensed wave which in turn my required waves mixes with all unwanted waves.

Please recommend me a solution or circuit or multiplexer / demultiplexer for switching piezos nearly below 1 us.

Thank you,

Akshay Kolekar

  • All muxes become worse at high frequencies. What is the frequency of your waves? How much crosstalk can you tolerate?

  • In reply to Clemens Ladisch:

    I am getting a clean wave at output of multiplexer. My frequency is of 500kHz. There should be no crosstalk as far as possiple.

  • In reply to Akshay Kolekar:

    Hi Akshay,

    What is the supply voltage of your system?

    I agree with Clemens, the off isolation/crosstalk become worse at higher frequencies. What is the worst case signal that you can tolerate at the output?

    Could you send a block diagram of your system? I want to understand what voltage waveforms are expected at the input and output of the mux.

    Could you please capture and send the input and output waveforms from your oscilloscope when the switch is off?

    Thanks,

    Kate

  • In reply to Kate Dickson:

    Thank you for your reply. I self discovered a solution for my problem by a combination of CD4052 ic. Well in my case there is no crosstalk and my exitation wave is clear and does not has any noise.

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