vmanj said:
At the point R1 / R10 - 44V.
At the point R1 / C2 / CAPSULE - 28V.
To reduce the measurement load, I use the 1Gohm resistor.
It turns out you can slightly reduce the value of the resistor R1 to slightly raise the voltage on the capsule ?
Probably not ..... even with a 1Gohm resistor in series with your measurement probe, you will still be loading the capsule input by a small amount. (1G + the input impedance of the meter)
So making R1 a lower value will certainly let you apparently measure higher volts at the capsule, simply because your meter will be loading the test point slightly less.
When C2 and the capsule are fully charged - and assuming neither 'leak' at all - there is essentially no current flowing in R1, so in theory its value is academic.
In practice there will be some small leakage and there will be a very small current - and hence a small voltage drop - across R1.
But reducing it's value slightly is unlikely to make any real difference. It might reduce the sensitivity a tiny bit? (the capsule is now essentially working into a slightly lower impedance).
If you double the voltage across the capsule from - say - 30V to 60V,and maintain the original value of R1, you would increase the sensitivity by 6dB.
(It's a useful way of creating some 'noise free' gain - assuming the capsule doesn't collapse with 60V of bias!)
But if you only increase the capsule bias volts by 10 V or so, you'd only increase the sensitivity by around 1 or 2dB - probably not worth the trouble?