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INPUT RC NORMALIZER
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Geoff Blake
On Fri, 5 Jan 2007, Jerry Massengale wrote:
Greetings,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. HTH 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. See <> ------------------------------------------------------------------------------ This E-mail and any attachment(s) are strictly confidential and is intended solely for the addressee(s). If you are not the intended recipient please notify <postmaster(at)palaemon.co.uk> and the sender by return and permanently delete the message. You may not disclose, forward or copy this E-mail or any of its attachments to any third party without the prior consent of the sender. ------------------------------------------------------------------------------ |
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Geoff Blake
On Fri, 5 Jan 2007, Geoff Blake wrote:
The input normaliser is a series 1M ohm / 47pF capacitor placed inCORRECTION 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. See <> ------------------------------------------------------------------------------ This E-mail and any attachment(s) are strictly confidential and is intended solely for the addressee(s). If you are not the intended recipient please notify <postmaster(at)palaemon.co.uk> and the sender by return and permanently delete the message. You may not disclose, forward or copy this E-mail or any of its attachments to any third party without the prior consent of the sender. ------------------------------------------------------------------------------ |
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you can measure scope input capacitance using a capacitance meter or bridge
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just remember to take the capacitance of your test leads or coax into account. i normally just measure the capacitance with the test coax disconnected and then with it hooked up the 1m ohm resistor shouldnt change the reading significantly. thats what the 130 lc meter was designed for . ive seen them used as general purpose measuring devices too. as you know the compensator will act as a 2x attenuator when driven from a low impedance source. you should terminate the pulse generator before the coax enters the compensator "i think" ----- Original Message -----
From: Geoff Blake To: hp group Cc: tekscope group Sent: Friday, January 05, 2007 11:24 AM Subject: Re: [hp_agilent_equipment] INPUT RC NORMALIZER 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. See <> ---------------------------------------------------------- This E-mail and any attachment(s) are strictly confidential and is intended solely for the addressee(s). If you are not the intended recipient please notify <postmaster(at)palaemon.co.uk> and the sender by return and permanently delete the message. You may not disclose, forward or copy this E-mail or any of its attachments to any third party without the prior consent of the sender. ---------------------------------------------------------- |
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