Hi Richard,
Alas, I think you may have learned the wrong lesson.
The proper lesson, IMHO, is don't connect the 410B's
AC ground clips to anything but a locally grounded,
chassis ground.
It's been a long time since I explored these meters,
and their problems, but there are some serious safety
issues, in my opinion.
The 410C is safer than the 410B, but in both, HP punted
on safety in my opinion.
Ordinarily, the 410's, in DC modes, have the guts of the
meter floating relative to the case. That means you can
get away with hooking the "common" lead to 400V relative
to ground, and still be safe.
AC wrecks all of that.
When the meter is put into the AC mode, the common lead
becomes connected to chassis ground, in preparation for
the grounded AC probe, and its body.
This can cause quite a surprise if you have the common
lead connected to something that is elevated from chassis
ground, as poof your meter's switch burns up.
At least with the "C" model, you can unplug the AC probe,
but you still can't solve the AC function position issue.
-Chuck Harris
On Tue, 18 Jun 2024 08:01:33 -0700 "Richard Knoppow"
<dickburk@...> wrote:
Well, you answered my question, namely how hot do the probes get.
The EA35 draws slightly more power than the 2-01C but both are close
to 2 Watts so probably probes with either will feel the same. I
wanted to make sure the correct voltage setting for the EA34 was 6.3
Volts and evidently it is.
The handbook is full of warnings about the meter chassis and
ground connections going to power line ground. I have a 3 to 2
adapter on the power plug to mine. Actually, I learned about this
problem long ago when my main mentor blew his 410B up by grounding
something.
On 6/18/2024 6:51 AM, Chuck Harris wrote:
P = I x E
6.3V x 0.3A = 1.9W
The probe's body provides a bit of heat sinking, but the 2W has
to go somewhere.
Cradle your hand around a 2W resistor running full power, and
get back to me ;-)
Heat is the main reason why 410C's are always missing their AC
probes. The probe gets uncomfortably hot, so it gets removed
and stored in a safe place when it not being used.... never to
be found again.
The other reason the probes get removed and lost is they are
practically useless for everyday measurements. The probe body
is also the probe's grounded return lead. It isn't safe to
willy-nilly ground AC power circuits, as you have to do to use
this probe.
-Chuck Harris
