R
[email protected]
- Jan 1, 1970
- 0
Hello,
do you know the operating principle of the keithly 640 electrometer?
I know there is a very sensitive electrometer using a membrane with a
capacitor plate on one side. To this plate the DC voltage to be
measured is applied + a voltage at the resonance frequency of the
membrane (around 200 V).
The resulting force is proportional to (U_0+U_1 sin(wt))^2.
One the other side of the membrane another capacitor changes its
capacitance when the membrane oscillates. An AC coupled amplifier then
amplifies the result.
The description is from the following interesting paper:
Vibrating Membrane Electrometer with High Conversion Gain
John Dimeff and James W. Lane Rev. Sci. Instr. 35 p666 1964
http://scitation.aip.org/getpdf/ser...35000006000666000001&idtype=cvips&prog=normal
The Keithly manual
http://www.keithly.com/com/data?asset=5685
shows the same principle, but is says the membrane is excited at 400
kHz but resonates at 6 kHz.
Many thanks
Daniel
do you know the operating principle of the keithly 640 electrometer?
I know there is a very sensitive electrometer using a membrane with a
capacitor plate on one side. To this plate the DC voltage to be
measured is applied + a voltage at the resonance frequency of the
membrane (around 200 V).
The resulting force is proportional to (U_0+U_1 sin(wt))^2.
One the other side of the membrane another capacitor changes its
capacitance when the membrane oscillates. An AC coupled amplifier then
amplifies the result.
The description is from the following interesting paper:
Vibrating Membrane Electrometer with High Conversion Gain
John Dimeff and James W. Lane Rev. Sci. Instr. 35 p666 1964
http://scitation.aip.org/getpdf/ser...35000006000666000001&idtype=cvips&prog=normal
The Keithly manual
http://www.keithly.com/com/data?asset=5685
shows the same principle, but is says the membrane is excited at 400
kHz but resonates at 6 kHz.
Many thanks
Daniel