This is a simpler issue but I need some help nonetheless. I have been carrying out an investigation on how the dielectric size of a capacitor affects its time constant. In theory the larger the dielectric the smaller the capacitance and therefore the smaller the time constant. However although im changing my dielectric by 5 mm at a time every single time I have measured the time constant with an oscilloscope I get the same value for the time constant of 302 ms which is also off of the theoretical value by a factor of ten. I think it may be due to the fact that my capacitor is in the pico farad range therefore it is hard to measure acureately.