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Roney

How to connect the pModIA to read impedance?

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Please, I need information about pModIA impedance analyser. I am using Arduino UNO connected to a pModIA to measure impedance. The Arduino codes work with some modifications of ChipKIT example. My question is how to do the calibration? Could someone send me a picture or schetch showing how to make pModIA connections to the component under test (DUT)? My project is very simple, I just want to measure the impedance of a fixed resistor at different frequencies. I'm having difficulty in understanding the connections and using the pModIA to measure this impedance. The pModIA manuals show no illustration of how to make the connections. For example, I will use only one SMA connector or, simultaneously, both connectors? I need a step by step tutorial. Someone could help me? Thank you.

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Hi Roney, 

I didn't personally create that manual or library for the PmodIA, but I'll do my best to help you out. (the most up to date version of the reference manual, although it is still being worked on, can be found on our wiki here)

As you noticed, what you'll first need to do is perform a calibration of the component in order to calculate the gain factor which will then be used in subsequent frequency sweeps. However, as the library currently stands, you are only able to perform a frequency sweep with a certain excitation voltage range (1V peak to peak).

To use this default configuration, what you will need to do is apply your "ground" voltage (GND on the Pmod header, J1) to SEL (the J2 pin). We will then to connect a 100k ohm impedance (again, because of how the library currently is) between the J3 SMA connector and the J4 SMA connector. J3 is where the frequency is emitted from the PmodIA, and J4 is where the returning frequency is received by the PmodIA. You can connect to the SMA connectors by an SMA cable if you happen to have one, or you may use a single pin of those 100 mil spaced male pin headers that are commonly used with microcontrollers to put into the central pin of the SMA connector.

Within the example code (you will need to use the library provided on our wiki here; I had to make a small change to the existing library that you originally were using to ensure the default setting worked correctly, you will need to make the same changes as before to work with your Arduino board) you will then need to perform the two point calibration (character 'c').

After that, you are free to attach your unknown impedance between the two central points of the SMA connector. However, (again because of this library that I am working on fixing so that the PmodIA can be used to it's full potential) the impedance will have to be between 6k Ohms and 10M ohms (the upper limit) in order to avoid saturating the ADC that is inside the Analog Devices chip (at least according to their datasheet).

Let me know if you have any more questions.

Thanks,
JColvin

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I bought your PmodIA module with the board of Renesas RL78 / G13.

 

I followed the instructions that I found here https://wiki.analog.com/resources/tools-software/uc-drivers/renesas/ad5933#downloadslink

 

I compiled the code and  debugged but still  have a problem.

 

I connected it, it reads the temperature but the impedance just does not work.

I connected a resistor between the center of the J3 connector and the center of the J4 connector.

I also tried to change the gain by adjusting the signal SEL and then switching the gain of R7 and R8.

 

Do you have any ideas why it always reads 0 impedance ??

I have to do before calibration with 47K.


If I need to do calibration as I do?

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