- #1
^zilla^
- 3
- 0
Hi all,
I've been struggling with an issue for a while and have finally admitted that I am in over my head and need some help :)
here's the situation.
I have a string of variable capacitors; all in parallel. let's say for this example that there are 100
each cap is connected to it's own ground, but can be measured at any given time. The injection voltage is small - 5V AC with a frequency that can range from less than 100 kHz to over 300 KHz.
The phenomenon that I am observing is this:
At "high" frequency, if we set all of the caps to the same value C1 and measure all of them there is a gradient in the voltage drop from 1 to 100 (left to right)
At "high" frequency, setting all of the caps to C1 and measuring capacitor 100 will give a different reading compared to grounding capacitors 1 thru 99 and only having cap 100 set to C1
the same test at "low" frequency sees almost all of these effects disappear.
Obviously this has something to do with the frequency of the injected signal and coupling between capacitors. I've tried to model this using some circuit LT spice, but wasn't able to replicate what I'm seeing empirically.
Does anyone have any ideas or suggestions?
many thanks
Tim
I've been struggling with an issue for a while and have finally admitted that I am in over my head and need some help :)
here's the situation.
I have a string of variable capacitors; all in parallel. let's say for this example that there are 100
Code:
V -------------------------------------------
| | | | | | | | | | | | | |
= = = = = = = = = = = = = =
| | | | | | | | | | | | | |
------------------------------------------
1 2 3 . . . . . . . . . . . 100
each cap is connected to it's own ground, but can be measured at any given time. The injection voltage is small - 5V AC with a frequency that can range from less than 100 kHz to over 300 KHz.
The phenomenon that I am observing is this:
At "high" frequency, if we set all of the caps to the same value C1 and measure all of them there is a gradient in the voltage drop from 1 to 100 (left to right)
At "high" frequency, setting all of the caps to C1 and measuring capacitor 100 will give a different reading compared to grounding capacitors 1 thru 99 and only having cap 100 set to C1
the same test at "low" frequency sees almost all of these effects disappear.
Obviously this has something to do with the frequency of the injected signal and coupling between capacitors. I've tried to model this using some circuit LT spice, but wasn't able to replicate what I'm seeing empirically.
Does anyone have any ideas or suggestions?
many thanks
Tim
Last edited by a moderator: