On Fri, 5 Jan 2007, Geoff Blake wrote:
The input normaliser is a series 1M ohm / 47pF capacitor placed in
series with the scope input. It should be as close to the input as
possible. There should be no coax between the input and the
compensator. The 47pF is normally something like a 39pF plus a
trimmer capacitor to set exactly to 47pF. The Tektronix devices
use a chassis mounted male BNC with the C/R soldered to the pin.
It acts as a potential divider and the input capacitance of the
scope is adjusted on an input squarewave, just like compensating a
scope probe.
CORRECTION The series element comprises a 1.0 Mohm and 47pF in
parallel, not as I wrote. I wrote that at work and was interrupted
by about a dozen telephone queries as I wrote.
It is thus:
47pF
|-----||-----|
generator o---| |---o to scope o----|---|-->
|---/\/\/\---| | \ input
1M | / circuit
= \ of
| / 'scope
| \
o--------------------o o----|---|-->
Sorry for the error.
Geoff
--
Geoff Blake G8GNZ located near Chelmsford, Essex, U.K.
Please reply to: geoff (at) palaemon (dot) co (dot) uk
Using Linux on Intel & Linux or NetBSD on Sun Sparc platforms
Please avoid sending me Word or PowerPoint attachments.
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