# Cause of difference in theoretical and experimental values of RC time constants

What accounts for the slight difference in the theoretical and experimental values of the time constant in a simple RC filter? The slight difference was just (.5*10^-4) seconds

• Can you add a circuit diagram (edit your question, then hit CTRL-K)? Also be more specific about the amount of difference that you observe and how you measure it. – jippie Sep 22 '13 at 7:50
• Okay. I've edited it. It's a simple circuit, sorry I'm kinda new. @jippie – Sakamoto Sep 22 '13 at 7:53
• So what you are saying is you expect $1500 × 100 \cdot 10 ^{-9} = 150 \cdot 10^{-6} [\text{s}]$ and you somehow found a difference of $9 \cdot 10^{-6} [\text{s}]$, is that correct? Question still is how you measured this. – jippie Sep 22 '13 at 8:01
• @jippie sorry! I've written the wrong values for the difference. I wasn't looking in the same circuit. I've edited it now. The difference was 5*10^-4 [s]. – Sakamoto Sep 22 '13 at 8:04
• Now you confuse me, you expect $\tau = 1500 × 100 \cdot 10 ^{-9} = 150 \cdot 10^{-6} [\text{s}]$ and you call a difference of $500 \cdot 10^{-6} [\text{s}]$ "slight"?! That is 300% wrong. You should really be more specific what you are measuring and how. – jippie Sep 22 '13 at 8:13