[Amps] Neon xfmr for HiPot

[Carl]

Excellent point Colin and good HV and high value resistors have been 
available from Ohmite for several years at low cost and up to 20KV, 2.5W, 
and in the $5 range at Mouser.

Since its not a good idea to use the metering string as a bleeder also, that 
needs to be added.

Plus the current limiter to the DUT is another HV resistor.

Parts multiply when trying to be safe.

Carl
KM1H

Carl
KM1H


----- Original Message ----- 
From: "Colin Lamb" <k7fm at teleport.com>
To: "Bill,W6WRT" <dezrat1242 at yahoo.com>; "AMPS" <amps at contesting.com>
Sent: Wednesday, July 18, 2012 12:04 PM
Subject: Re: [Amps] Neon xfmr for HiPot


> "and protect your analog meter with 2 diodes across the terminals."
>
> While Bill correctly states that the diode will not work across most 
> meters, because the voltage will not be high enough, and does outline how 
> to correctly install the diodes, it seems that we have forgotten about the 
> use of this particular meter.  The circuit has a large resistance which 
> limits current.  Because current is limited, it can never exceed the 
> current rating of the meter - hence the diode protection is not necessary.
>
> Current indicating meters on a high pot are never more than 50 ua fs 
> (which would be in the neighborhood of 1700 ohms), but they would be used 
> only be if more desireable 10, 15 or 20 ua meters are not available.  The 
> current limiting resistors must be bulletproof.  If they fail, the loss of 
> the meter is almost irrelevant.
>
> 73,  Colin  K7FM
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