Re: Electrostatic Meters - AC not possible

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
 >
 > Original poster: "Richard Wayne Wall by way of Terry Fritz 
<twftesla-at-qwest-dot-net>" <rwall-at-ix-dot-netcom-dot-com>
 >
 > List,
 >
 > There are two types of inputs for the Sensitive Research electrostatic
 > meters dependant on their age.  Essentially newer models have a diode
 > system and will measure AC as well as positive DC.  Also note the nonlinear
 > voltage scale on the front of the meter allows for the nonlinear force
 > measurement between the two capacitor plates.
 >
 > RWW

	Sounds as if that meter has included the rectifier so it COULD measure
peak, and therefor would seem to need some sort of bleeder resistor
across it to set the time constant with which to measure the peak.
Diode and/or bleeder leakage would negate the main advantage of ES
meters - ultra high input resistance.  On the subject of ES meters I
looked at Bureau of Standards Circular No. 74, and found specific
references to the use of "electrometers" (same configuration, higher
sensitivity) to measure RF voltage.  Also mentions a simple form of
electrodynamic ammeter which can work at high frequencies.  I'll post
the reference from another site. These things are mentioned as
"sensitive" devices, with no definition of what sensitivity means.
There is a statement to the effect that it is necessary to use a large
capacitor in parallel with the ES device, because of its extremely low
input capacitance.  The configurations shown in the book look as if they
would be easy to duplicate at home.  I can't see how either instrument
could fail to give readings of the RMS value of the quantities being
measured.

	Either should work with a CW VTTC, where the RMS value is meaningful,
but wouldn't give a useful answer for the typical disruptive TC.  Of
course, as with any high-voltage measurement, corona and/or leakage can
give phony answers.  I can't see any way to measure a decent TC without
running into these problems.

Ed