Why are there covering caps on my DMM probes?

[jtruc34]

There are covering caps which cover about 90% of the tip, and on which it is written 1kV Cat-IV. If I remove them, it is written 1KV CAT-II.

If it is just a safety feature to prevent my fingers to touch the tips, I don't see how it is related to CAT rating which does not have to do with the probability of me touching something (or does it?).

Or is it something that plays another role, like preventing arc formation or something like that?

Thank you.

[Nerull]

The ratings specify a minimum distance between you and exposed conductors.

[jtruc34]

What surprises me is that they are only CAT-II without those caps while I saw Fluke CAT-IV test leads of which the metal tips were not particularly further from the fingers than with mine (Brymen BL21S2-T4SC).

[Doctorandus_P]

Those probe condoms are for compliance to some kind of law, but are a nuicanse to use.
That is why they are on the probes when you buy them, but can be easily removed and thrown away.

A small minority of people seem to think they are usefull for preventing accidental shorts, and I have to admit, a few months ago I accidentaly shorted an 100V 17mF elco and that was pretty scary. It also burned a hole in the side of the probe of almost half it's diameter.

[SG-1]

They are there to prevent arc formation between the two probes exposed metal or a single probe & earth or another energized conductor,  which in a cat 4 environment would be a life altering event if you survive the blast & fire. It is uncomfortable in a cat 2 environment & generally discolours what ever you are probing.

I agree they do get in the way from time to time. I try to work with them on & only remove one of them when needed.  I saw a guy take his own picture yesterday.  Fortunately his head blocked my view of the arc. The temporary blind spot in his vision eventually went away. 

[ejeffrey]

What surprises me is that they are only CAT-II without those caps while I saw Fluke CAT-IV test leads of which the metal tips were not particularly further from the fingers than with mine (Brymen BL21S2-T4SC).

That requirement is fairly new (5-10 years? I don't remember).  Older equipment rated for CAT-IV at the time of manufacture doesn't require those covers.  Probably those fluke test leads just predate the updated standard. 

I usually take them off because I almost never work in anything but a CAT-II environment.  If I went probing around in distribution panels or high power circuits I would put them back on.