i there,
i'm a big noob and in love with this forum.
At this moment i'm willing to measure capacitance with the highest accuracy possible. I'm gonna do this with an LC circuit and the material available (function gen. / oscillloscope / multimeters and so on). I've got the following inductors:
2.2 uH / 1% / 0.04 ohm
10 uH / 1% / 0.15 ohm
1 mH / 3% / 33 ohm
10 mH / 5% / 72 ohm
I'm willing to measure capacitors in a range of 100 nF to 10 mF with 5 percent accuracy.
For another part of my measurement setup (4 points resistance measurement with probe holder etc.) i've used the inner connections of BNC cables for all leads. In this case i can minimalize parasitic inductance/capacitance. At the measurement devices i short one of the inner connections with the outer shield so they come together in one 'connector'.
The capacitors to be measured are probably inkjet printed. So these will be measured with the same probe setup as well. I can simply raise the frequency of a sine wave to look for a peak in the amplitude of the voltage on the scope. In that way i can find the resonance frequency from which i can determine the Capacitance with a known L. My function gen. has an impedance of 50 ohms. I hope i've been clear enough about my situation, i'm a little bit in a hurry with all this stuff.
Now i've got a few questions:
- Is it in my case better to use a series or parallel circuit for this measurement setup? I know i can find a peak in the amplitude with a sweep in both cases. But which one would result in better accuracy. I also don't really understand what the influence of a resistors in series with a parallel tank circuit is.
- I find it difficult to approximate my accuracy. I don't know how to take into account the inaccuracy of looking for a peak on the scope. Is this a few hundred Hz, a few thousand?
The way i'm looking for this peak is setting the timebase very large so that the sine appears as a big dense line. Then i put the volts per division as high as possible and sweep manually around my resonance frequency until i found the best matching frequency (or so the highest peak visible).
- These inductors i've got have axial termination so i have to use a breadboard to develop this circuit. Can anyone help me how much influence things like this will have on my measurement accuracy. I can imagine that although i use BNC cables for the connection from the breadboard to the capacitor, these make no sense at all when using a breadboard and a inductor with those large leads going trough the breadboard. These must bring a lot of parasitic properties with them.
I will post some pictures of my measurement setup as well. Thanks in advance!!!
Moderators note : Please upload pictures to forum next time
i'm a big noob and in love with this forum.
At this moment i'm willing to measure capacitance with the highest accuracy possible. I'm gonna do this with an LC circuit and the material available (function gen. / oscillloscope / multimeters and so on). I've got the following inductors:
2.2 uH / 1% / 0.04 ohm
10 uH / 1% / 0.15 ohm
1 mH / 3% / 33 ohm
10 mH / 5% / 72 ohm
I'm willing to measure capacitors in a range of 100 nF to 10 mF with 5 percent accuracy.
For another part of my measurement setup (4 points resistance measurement with probe holder etc.) i've used the inner connections of BNC cables for all leads. In this case i can minimalize parasitic inductance/capacitance. At the measurement devices i short one of the inner connections with the outer shield so they come together in one 'connector'.
The capacitors to be measured are probably inkjet printed. So these will be measured with the same probe setup as well. I can simply raise the frequency of a sine wave to look for a peak in the amplitude of the voltage on the scope. In that way i can find the resonance frequency from which i can determine the Capacitance with a known L. My function gen. has an impedance of 50 ohms. I hope i've been clear enough about my situation, i'm a little bit in a hurry with all this stuff.
Now i've got a few questions:
- Is it in my case better to use a series or parallel circuit for this measurement setup? I know i can find a peak in the amplitude with a sweep in both cases. But which one would result in better accuracy. I also don't really understand what the influence of a resistors in series with a parallel tank circuit is.
- I find it difficult to approximate my accuracy. I don't know how to take into account the inaccuracy of looking for a peak on the scope. Is this a few hundred Hz, a few thousand?
The way i'm looking for this peak is setting the timebase very large so that the sine appears as a big dense line. Then i put the volts per division as high as possible and sweep manually around my resonance frequency until i found the best matching frequency (or so the highest peak visible).
- These inductors i've got have axial termination so i have to use a breadboard to develop this circuit. Can anyone help me how much influence things like this will have on my measurement accuracy. I can imagine that although i use BNC cables for the connection from the breadboard to the capacitor, these make no sense at all when using a breadboard and a inductor with those large leads going trough the breadboard. These must bring a lot of parasitic properties with them.
I will post some pictures of my measurement setup as well. Thanks in advance!!!
Moderators note : Please upload pictures to forum next time
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