# How to measure the R & c value individually?

Discussion in 'General Electronics Chat' started by PSIR, Nov 8, 2010.

1. ### PSIR Thread Starter Member

Apr 23, 2008
29
0
Hello everyone

Please take a look at the attached schematic.

There is a 50KHZ AC signal connect to a R-C circuit. Also, There is a instrument amplifier circuit on the right side. The amplifier is able to amplifly the voltage of the R-C circuit. So that I could figure out the Impedance (Z) of the R-C circuit.

According to the formula of electrical Engineering. Z=√The square of R + The square of Xc

While I figure out the value of Z. How to separate the value of R and Xc individually?
If I could get the the value of Xc. Then the value of Capactive can be calculated.

Bset Regard

Thanks!

• ###### Impedance measurement.jpg
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Last edited: Nov 8, 2010
2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
293
The most accurate way is to remove the component from the circuit and then measure it.

3. ### shteii01 AAC Fanatic!

Feb 19, 2010
4,441
704
Measuring capacitance, C, is hard. I think some of the more expansive multimeter have option to measure it, otherwise you just rely on what is printed on the capacitor.

4. ### PSIR Thread Starter Member

Apr 23, 2008
29
0
Excuse me. I couldn't posted my schematic on it.
Could any body tell me how do I post my schematic.
Thank you.

Last edited: Nov 8, 2010
5. ### PSIR Thread Starter Member

Apr 23, 2008
29
0
Thank you everybody. Finally, I find out the way to up load the schematic file.
Press the "Edit" button then Press the "Go Advanced" button.
So that you can brouse and up load the file what you want to post.

6. ### shteii01 AAC Fanatic!

Feb 19, 2010
4,441
704
Probably the easiest is to take the screen shot of the schematic while it is on the screen by pressing Print Screen key on your keyboard, then open Paint and click paste, save the picture in Paint as a jpeg, upload it here as an attachment when you make a post.

7. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
If you have access to the individual R & C components you need to take one or more additional measurements.

One option is to first measure the resistor voltage, VR.

The current in the circuit is then I=VR/500.

Next, measure the capacitor voltage, Vc.

The capacitive reactance, Xc is then Xc=Vc/I=(500*Vc)/VR

As you indicated, C may then be calculated using Xc and the known source frequency.

There is at least one other possible approach. But your one suggested measurement of the source voltage won't be sufficient.

Last edited: Nov 8, 2010