# Circuit analysis

Discussion in 'Homework Help' started by Cerkit, Feb 25, 2009.

1. ### Cerkit Thread Starter Senior Member

Jan 4, 2009
286
3
Hi. I need to be able to find the value of the following capacitor and resistor. The circuit is in a box so I only have access to node1, node2 and ground. I am not allowed to use an oscilloscope. I can only apply voltages and measure voltage or current at the output.

Code ( (Unknown Language)):
1.
2. N1 o-----||-----o N2
3.            |
4.            R
5.            |
6.      o----------o Gnd
7.

2. ### veritas Active Member

Feb 7, 2008
167
0
Well, measuring the resistor should be straightforward enough, so I'm assuming you're trying to measure the capacitor.

By far the easiest way to do that is to measure the RC time constant and calculate the capacitance from there. Without an oscilloscope, though, I don't know how you'd possibly get an accurate measure of the time constant.

What can you use to measure voltage/current? What can you use to supply voltage? If you have a function generator, you could probably make a rough estimate by finding the frequency cutoff of your circuit (it's a high pass filter).

3. ### KL7AJ AAC Fanatic!

Nov 4, 2008
2,208
427

I'd definitely go for the cutoff frequency method.

eric

4. ### Cerkit Thread Starter Senior Member

Jan 4, 2009
286
3
Only able to apply dc or ac 10 V. measurements made using an adc which is interfaced with a xilinx chip.

5. ### veritas Active Member

Feb 7, 2008
167
0
Can you vary the freq. of your 10VAC? Also, if you can record the voltage measurements on the FPGA fast enough, you could measure the RC response.