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

[Jim Wiley]

They are worried about lawyers and lawsuits.  And rightly so.  Too many 
lawyers with not enough to do.

I have such a probe (the 80K, which is rated for use up to 6000 volts), 
and use it to read the anode voltage of a 3-1000Z amplifier  (or other 
HV circuits) from time to time.  But, I am very careful - I make sure 
the B+ is off, attach the probe, back completely away from the probe and 
meter, turn the B+ on, make the measurement, turn the B+ off, remove the 
probe, and button things back up.

Unfortunately, in today's world, there are still many candidates for a 
Darwin award.   Common sense is not all that common, it seems.

- Jim, KL7CC


On 1/7/2015 8:55 AM, Mike A wrote:
> 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.
>