Re: Fluke 8600A -- a new question about calibration



"Phil S." wrote:

I put a "precision" 1 ohm resistor on both meters this morning. The
Tripplett reads 1.3 ohms and when its leads are crossed, they read 0.3 ohms,
telling me that the Tripplett doesn't correct for the inherent resistance of
the probe leads. This is an auto ranging meter. That's also why the
Tripplett tells me the 2.7 ohm 25W sandblock is 3.0. I've been aware of
this since I got the meter.

The Fluke reads that resistor correctly at 1.0 when manually set to the
upper ranges. The low ranges (200z, 2k, auto) seem to have a problem with
this internal resistance of the probes and possibly part of the circuit,
displaying in excess of 2 ohms. Is this an issue the calibration tech will
consider in what he does to calibrate the meter, or what?

If this won't change, the incentive to pay for calibration goes way down.
If I am reasonably sure setting the meter to a higher range will get my
question answered with reasonable accuracy, then, I'm thinking, why bother
and why spend the money? I don't have a burning desire to know the meter is
99.999999% accurate.

Those of you who have any sense of my mindset must know that I'm a bargain
hunter. It's kinda like the smoke in a tranny, once you let it out...if I
have to spend too much to get this meter in shape, it takes the fun out of
it. Truthfully, though, even if I spend a few bucks, it looks like I get to
have a good pro-grade meter on my bench and I've been wanting that for a
while.

I"m on the fence with sending it for calibration. So, just taking opinions
here a second time and just trying hard to set my expectations
appropriately..

Thanks.

--Phil

Phil, every bargain has its price.

A calabrated piece of gear has its value.

Keep subtracting the probe resistance, and stay with the Tripplett?

With my 8600A, I always have to account for the probe resistance in the low range. Circuit contact
points have to be made correctly, and the meter side plugs have to be spun around a few times to
insure good contact.

THAT, goes with territory with any meter used in the very low resistance ranges.

When I got my 8600A, it had been cal'd, and the probes when shorted would read zero. A few days
later, it would read .1. Twist the plug ends in the meter, and its back to zero again.

Clip leads to the chassis from the meter ground side in low resistance measurements are never good
practice in low resistance measurements. Very hard and extremely sharp probe tips on the contact
side is the only way to make good probe surface contact in the low resistance measurment game.

Your measurement technique becomes very important, even when you have the best set of probes.

When you pinch the leads of a resistor to the ends of the meter probes, did you scrape down the
resistor leads to get all the oxide off for good meter contact?


Check yourself out.



Regards,

Rich Koerner,
Time Electronics.
www.timeelect.com

Specialists in Live Sound FOH Engineering,
Music & Studio Production,
Vintage Instruments, and Tube Amplifiers
.

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