I am stuck with my project. I have to measure the frequency characteristics of an unknown impedance valued sensor.
How to do that ?
Do you have the AD5933 evaluation board (EVAL-AD5933EBZ) with you?
The AD5933 evaluation board is a test system designed to simplify the evaluation of the AD5933.
Or are you going to design your own custom board?
Yes, I have EVAL-AD5933EBZ board with me.
Is EVAL-AD5933EBZ and AD5933 both are different ?
I cannot interface AD5933 chip with other devices using EVAL-AD5933EBZ board.
What do you mean by custom board ?
EVAL-AD5933EBZ is the evaluation board of AD5933, while AD5933 is the chip itself.
You can interface other external devices to the EVAL-AD5933EBZ board using the available test points/nodes at the board. What other device(s) are you thinking of using together with AD5933?
A custom board is your own designed board.
How to interface Arduino Uno board with Evaluation board EVAL AD5933EBZ ?
I cannot see any connections on the EVAL AD5933EBZ to be interfaced with other devices.
How to interface other devices with EVAL AD5933EBZ is my main question. Can you please explain that with the help of Pictures ?
For your question on test points for the serial programming (I2C) using Arduino board, that is right, there are no available test points. I think this has been responded on this thread: About SDA and SCL pins on AD5933 to interface with other hardware
As you requested, here are snapshots for your reference where to tap for SCL and SDA lines:
You can tap at R15 and R16 for the 2 lines.
Thank you very much for your response.
I have an other question.
What do you mean by calibration setup ? Do I need to calibrate the board every time I set up ?
For Example, I have put 15 pf capacitor to measure its impedance characteristics. But its not showing the correct magnitude and phase delay by -90 degrees.
For any capacitor, the magnitude of impedance must decrease with increase in frequency. But When I connect a capacitor in Z and change capacitor value to 15 pf in Complex impedance section, I am not getting the correct characteristics that normal capacitor exhibit.
Do I need to change the value of Capacitor to 15 pf in the Calibration Impedance section of EVAL AD5933EBZ software ?
Please make clear why Rfb(Feedback resistor) is used ?
Apologies for the delay. I have overlooked your follow-up question.
The board should always be calibrated for a change in any of the following parameters:
The board is calibrated again because there would be a change in the gain factor when any of the above mentioned parameters is changed.
The Rfb is used so that the ADC will not be saturated.
We tried to measure an unknown capacitance by using 150k for Rfb and 210k for Rcal. The same procedure for calibration that was done in measuring an unknown resistance was used.
Then the capacitor was placed on Z and the Start Sweep button was pressed. This is what we obtained:
You can download impedance data and compute the capacitance by using the formula:
Xc = 1/(2*pi*f*C)
From the impedance data, we chose a frequency of 30 kHz and an impedance of 342765.3. We obtained a capacitance value of 15.48pF.
Hope that helps.
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