# Measuring magnitude and phase in an RC circuit

Discussion in 'Electronics Homework Help' started by coilin_wilson, Apr 29, 2017.

1. ### coilin_wilson

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Apr 29, 2017
Hi everyone,

I was given a project to do by my professor to measure the magnitude and phase of an RC circuit (1 resistor, 1 capacitor) through the Arduino Uno IDE. I am just new to Arduino and I hoping someone could point me in the right direction.

Thanks,
Coilin

2. ### Bluejets

4,991
1,048
Oct 5, 2014
Monitor the voltage and output on serial monitor perhaps?

Arouse1973 likes this.
3. ### Harald KappModeratorModerator

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Nov 17, 2011
What kind of RC circuit (low pass, high pass)?
What have you done so far to tackle this task?
What does your circuit look like?
Which are your ideas how to proceed?
What frequency range? You are aware that magnitude and phase of an RC filter are frequency dependend, aren't you?

4. ### coilin_wilson

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Apr 29, 2017
Hi Harald,

It is a low pass filter,

So far I have made calculations and used Multisim to confirm my answers to make sure they are correct.

The circuit is just 1 resistor, 1 capacitor built on breadboard that will be programmed and powered through Arduino Uno.

I was wondering if there was a program available to do this project or if not what way I should do it.

From 0Hz to 10kHz

Thnaks,
Coilin

5. ### Harald KappModeratorModerator

11,662
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Nov 17, 2011
I think you should develop that program as part of the task.

As usual there is not on ebest way to do this, there are several ways. Do you use an external waveform generator? Note that you cannot use the areduino's analogwrite function here as it outputs pwm at a frequency of ~500 Hz or 1000 Hz, depending on the specific arduino.

I see an issue with the frequency range: The arduino takes about 100µs to read an analog input which limits the sample rate to approx. 10 ksamples/second. To sample a 10 kHz signal you'd need at least 20 kHz (or more) to fulfill the Nyquist-Shannon theorem. The arduino thus limits your measurements to 5r kHz or less.