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Re: [TenTec] OT: Scopes

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] OT: Scopes
From: Ken Brown <ken.d.brown@hawaiiantel.net>
Reply-to: ken.d.brown@hawaiiantel.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 20 Feb 2012 12:23:58 -1000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

> If I want to look at ripple on 
> a B+ I guess I'm fine up to...maybe 750 VDC with a 10x probe rated for 
> that kind of voltage.
> I see thay do make HV scope probes also.
I would suggest building into the HV supply a voltage divider with at 
test jack for monitoring the ripple. You may want to design it for 100X 
voltage division instead of only 10X. You need to use resistors that are 
rated for the voltage, and power that they will be subjected to. This 
voltage divider resistor setup could double as the bleeder resistor.

For example a 3 kV plate supply for an amplifier might have a 600 k Ohm 
bleeder resistance across the output. If that resistor was made from 
some some combination of resistors adding up to 594 k Ohm, with the 
remaining 6 k ohm in series on the ground end, you would have a 100X 
voltage division. The test point at the hot end of the  6 k Ohm resistor 
would have 30 V on it when the HV supply is 300 V. Using the scope in AC 
coupled input mode you could easily look at 1 Volt ripple levels, using 
the 10 mV/div scale on the scope.

A potential hazard (pun intended) is the 6 k Ohm resistor opening up, 
resulting in the full 3 kV appearing at the test point.

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