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Dear Sir

Thanks a lot for the reply and extensive explanation, highly appreciated Sir

Resolution:    I need the resolution of  0.1% , so for that  that i will select more than 15 Bit ADC. I don't know this is achievable or not.

Precision: I also need the precision of 0.1%, if not possible it should be less than to 0.5%.

Accuracy: i need 0.1% as well

• Minimum Impedance: 1 MΩ
• Maximum Impedance: 30 MΩ

Change Detection Requirement:

• 0.1% of Minimum Impedance:0.1%×1 MΩ=0.001×1 MΩ=1 kΩ
• 0.1% of Maximum Impedance:0.1%×30 MΩ=0.001×30 MΩ=30 kΩ

I already generated the signal with DDS i will shift toward STM32 now

I will search about DMS because i don't and also on the software for calculation purpose.

I have a question

Can you draw the diagram of the circuit on the page with the pen, having components name only for my convenience.

In case of further questions, kindly let me know

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Dear Sir.

Thanks for the reply. If i follow this method of measurement,as you explain

My signal amplitude is 500mV and the impedance is 28 M ohm, so the current should be 17.9 nA.

but in my case i have to only measure the impedance, which is unknown in my case, i will then measure the current flow through the device and by ohm law measure the impedance , am i right ?

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Here's the revised version of your text with improved grammar:

---

Dear Sir,

I have a sensor made from a microfluidic device with a channel inside it. At the bottom of the channel, there are electrodes to which I will send the signal.

Initially, when I flow the antibody through the channel, the antibody attaches to the electrodes surface on the bottom of the channel, resulting in an impedance value of 8 MΩ. After some time, I flow the sample into the channel. The sample again attaches to the electrode surface, causing the impedance value to rise to 28 MΩ.

I need to provide a signal with an amplitude of 500 mV. However, frequency-wise, I will use two different values:

1. 100 Hz
2. 1 kHz

I will take measurements at these two frequency points at different time intervals. I will not sweep the frequency from 100 Hz to 1 kHz, and I do not need to measure the phase angle or other parameters.

I hope this clarifies the situation. If you have any further questions, please feel free to ask. Your comments are very valuable to me.

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Thank you so much sir for provide me the material, the PDF file is very valuable, highly appreciated

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Below, I have attached the equivalent circuit of my sensor.

Regarding the capacitance value, I don't know the exact value because we have only measured the impedance using an impedance analyzer. We have never measured the capacitance separately. When the antibody flows inside the sensor, the impedance increases to 8 MΩ, and when the sample flows, the impedance increases to 28 MΩ.

The signal amplitude is 500 mV, and we use two different frequency values at different intervals:

1. 100 Hz
2. 1 kHz

I am not going to sweep the frequency from 100 Hz to 1 kHz; I will just fix the frequency and take the measurements.

In terms of accuracy, there is no predefined requirement, but the best accuracy I have achieved is 0.1%. I plan to use an ADC with a resolution of more than 15 bits.

Your suggestions and any questions you may have are highly appreciated.

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Thank you very much for your reply.

I used the AD 5933 with an Arduino via I2C communication, where I shorted two jumper wires to transfer the data to the Arduino. I am attaching a picture of that setup as well.

I have also reviewed papers regarding the automatic calibration of the AD 5933, but I haven't been able to resolve the issue of automatic calibration. I will revisit this issue.

I even contacted the technical support team at Analog Devices, explaining that I wanted to measure impedance automatically from 1 MΩ to 10 MΩ. However, they informed me that it is not possible. I can provide you with the email correspondence with Analog Devices' technical support team if you share your email address.

If I could successfully measure impedance from 1 MΩ to 10 MΩ, it would significantly simplify my problem. My sensor has a maximum impedance of 28 MΩ and a minimum of 8 MΩ. I would use some parallel resistors with the sensor and create a comparison table. For example, if the sensor's impedance is 28 MΩ, I might measure 6 MΩ, and if the impedance is 8 MΩ, I might measure 1 MΩ. This comparison table would allow me to handle the complex situation much more easily. However, due to the need for repeated calibration of the AD 5933, I stopped using it, even though I was able to transfer the data to the Arduino by writing the code in C++.

If you could assist me in achieving automatic calibration of the AD 5933 for all impedance measurements between 1 MΩ and 10 MΩ without needing to repeatedly change the calibration resistor, I would greatly appreciate your help

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I even ordered the MUX as well, as i saw in one paper they used the MUX for calibration, but i failed to calibrate using that.

Have you achieved the automatic calibration of AD 5933 between 1M ohm to 10M ohm automatically and AD 5933 automatically measure the unknown impedance value lies between this range anywhere ?