hi there
I'm looking for a way to calculate value of capacitors of pF(pico Farad) range. the thing is when I use a RLC meter, looks like the device is limited to high ranges of pF to nF and so I can not measure value of for example 1pF...
I used this technique
using a microcontroller, I generate 8MHz pulse and pass it through first: a Lowpass filter and then: a peak detector
C1 is the value I'm trying to measure and it is around 1pF to 20pF(I do not knoe the right value, using this circuit I'm trying to measure it).
I've wired the circuit on a breadboard
then I use the equation Vo=Vs(1-exp(-t/tau))
Vs=3.3(STM32F103)
t=(here)62.5*10^-9
tau=R1*C1 and R1=4100ohm
I use a multimeter at the end of circuit where you can see "equivalent voltage"(I use a multimeter because it seems that it has no effect on my circuit for changing values due to very large input resistance ect.)
there are some issues:
1-it seems like the breadboard itself has some pF capacitor adding to my measurements(even for example if I just insert a piece of wire in a hole of breadboard)
2-it seems like the frequency also effects the value of output voltage and so the calculated value of C1.
can anyone help me with suggestions?
I'm looking for a way to calculate value of capacitors of pF(pico Farad) range. the thing is when I use a RLC meter, looks like the device is limited to high ranges of pF to nF and so I can not measure value of for example 1pF...
I used this technique
using a microcontroller, I generate 8MHz pulse and pass it through first: a Lowpass filter and then: a peak detector
C1 is the value I'm trying to measure and it is around 1pF to 20pF(I do not knoe the right value, using this circuit I'm trying to measure it).
I've wired the circuit on a breadboard
then I use the equation Vo=Vs(1-exp(-t/tau))
Vs=3.3(STM32F103)
t=(here)62.5*10^-9
tau=R1*C1 and R1=4100ohm
I use a multimeter at the end of circuit where you can see "equivalent voltage"(I use a multimeter because it seems that it has no effect on my circuit for changing values due to very large input resistance ect.)
there are some issues:
1-it seems like the breadboard itself has some pF capacitor adding to my measurements(even for example if I just insert a piece of wire in a hole of breadboard)
2-it seems like the frequency also effects the value of output voltage and so the calculated value of C1.
can anyone help me with suggestions?