Capacitance Meter

Question

I measured the value of some capacitors with an arduino capacitance meter shield i built. While I didn't expect the measured values to be exactly equal to the rated values, I noticed that the larger capacitors gave me readings that deviated much greater from the rated values when compared to the smaller capacitors. Can anyone give me a reason for this?

Former Member · Answer

The circuit is measuring the charging time of the capacitor. Here is the algorithm: http://code2flow.com/xp9FLZ.code.png

D_Hersey · Answer

Forgive John, he achieves mightily given the burden he is under: Lurking by the light of his twin Brett Farve - Bart Starr desklamps in the rec-room of his doublewide igloo, the literally beady eyes of the wall fauna gazing sternly, if uncomprehendingly, upon him. Red State blanket on the plaid couch. At least he isn't wasting his life constructing snippy little TLAs referencing his neighbors to the south as so many do. Or constructing ghastly/cool dioramas of squirrels playing cards by the flicking light of old beer signs. And now a word from RAP, PRAB! http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CCMQFjAC&url=http%3A%2F%2Fninova.itu.edu.tr%2Ftr%2Fd…

DAB · Answer

Did you make sure that the capacitors were fully discharged before you started? How accurate is your resistor? Did you accurately measure your voltages for charging and discharging. There are a lot of variables that you need to control for accuracy. DAB

jw0752 · Answer

Hi Michael - It might be interesting to graph your readings versus stated values for a range from small to large capacitances. This might give you a feel for how the readings are diverging and the rate of divergence. Sometimes this type of information can help locate and fix the problem. If you are using the Arduino for timing you might look closely at how you are doing the timing. I learned recently on this forum that delay() can sometimes throw things off. John

Capacitance Meter

Top Replies