Re: Fluke calibration

Stephen Cowell wrote:

"Rich Koerner" <richk@xxxxxxxxxxxxx> wrote in message
news:48E53E99.3F8EEE7D@xxxxxxxxxxxxxxxx


Stephen Cowell wrote:

"Rich Koerner" <richk@xxxxxxxxxxxxx> wrote in message
news:48E503F4.76F77FA4@xxxxxxxxxxxxxxxx


Stephen Cowell wrote:

"Phil S." <psymonds_no_spam@xxxxxxxxxxx> wrote
...

I put a number of different resistors on it. In the low range (22z,
50z,
100z, 125z, 150z, 250z) it's consistently 20-25 ohms high and in the
higher ranges it seems to do a little better, where I guess that
small
a
variance isn't as noticeable.. That looks like a calibration error
to
me,
but I don't know much.

Try replacing the low-measurement fuse... these can
be damaged without failing completely. As a short-
term troubleshooting test you can foil-wrap it and see
if your ohms come back down... don't run with it
like that unless you want a dead meter.
__
Steve
.


Steve, that is really bad advice. Tin foil
NOTHING!!!!!!!!!!!!!!!!!!!!!!

Use the Tripplett 9045 to measure it!!!!!!!!!!

It's not in a high-current location... it is a protection
fuse, meant to go when you ohm wall current or a
charged cap. Jeez, don't have a cow, Rich.


Yo!!!!!

There is a *suspected* input resistance that is the cause of a low
resistance reading error.

You suggest this fuse, for having this resistance.

Then, USE an OHM Meter and MEASURE IT!!!!!!!!!!!!!!

If the fuse is the one I'm guessing, then when
it fails it's not constant... the granules are partially
burnt, so you get a non-linear resistance effect.
You can't just use a 1/2A slo-blo, it has to be
that special silly granular fuse, it's the only one
fast enough to protect the meter yet low enough
ohms to not affect the reading. When they don't
get fully blown, they go ohmic, in a non-linear
way. If someone's put a regular 1/2A sloblo
in there it could have the same or similar symptoms...
temperature sensitivity, ohmic, etc.

The easiest way to verify that the measurement
fuse is not the problem is to bypass it. I've
troubleshot giant industrial burners and other
expensive equipment with a jumper wire... it's
a standard practice when you know conditions
are controlled enough to allow it. That's why
I told him not to run the meter with the fuse
shunted.

Simple test... if the measurement is still off
with the fuse shorted, then there's bigger
problems. If it works good, then you need
that $5 fuse.

Perzackly.

My Fluke 187/189s use a 440mA fuse for overcurrent protection
on the milliamp scales, and those suckers cost ELEVEN
BUCKS. (At least, that's what they cost a couple of years
ago...when the Fluke Nerd Squad descended on Castle
Vlave awhile ago to consult with The Lord on the new 287/289
meters, I bitched about it and they sent me a bag with about 25
of 'em in it, plus a half-dozen of the 11-amp ones that are used
on the high current range. I haven't bought any since.) Kind of
pisses you off if you kill an $11 fuse taking a plate current
reading on a $3 Chinese 6L6 that decides to short while
under test. (Doesn't happen very often, but it's still a pisser
when it does.)

BTW - that new 289 is stone fuckin' *killer*. Resolves
1/1000th of an ohm, logs events, massive software,
etc. I love mine. I was originally going to get a 287,
because I didn't need the event logging and a few other
things that are on the 289, but the hi-rez ohms function
is only on the 289, and I hadda have it. You know how it is.

I've bridged plenty of fuses with clip leads while testing.
99 times out of 100, it's not going to be a problem. For
that 100th time, it depends on whether or not you were
looking at the current meter on the Variac, and on how
fast you can reach the kill switch...

Lord Valve
Meter Addict (I have 12 Flukes, and a horde of others...egad....)


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