[Boatanchors] Fluke 80K high voltage probes... why "energy limited circuits" only?

[Mike A]

On Wed, Jan 07, 2015 at 05:26:45PM +0000, Rick Poole WA1RKT wrote:
> Fluke makes a popular family of high-voltage probes for DMMs, the 80K series
> (6, 15, and 40 KV). They're intended for Fluke's DMMs but are theoretically
> useable with any DMM with a 10-Mohm input impedance.
>
> For each of these probes, the instruction sheet emphasizes that "the probe
> can only be used to make measurements on energy limited circuits within
> equipment... DO NOT use this probe to measure high voltages on power
> distribution systems.".
>
> These probes are for measuring voltage, not current. So, why the restriction
> on power distribution systems? 5 KV is 5 KV for measurement purposes no
> matter if it is capable of supplying 1000 amps or 1 milliamp. So why should
> the voltage-measuring probe or DMM care if the voltage source is a power
> distribution system or not?
>
> Hard to tell if the plate voltage on a KW linear would be considered an
> "energy limited circuit" or a "power distribution system" within the context
> of that warning.

I wonder if they're worried about a flashover or sustained arc. I read "energy
limited" as "not enough energy available to sustain an arc or to flash over
dangerously". I Could Be Wrong. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin