Author Topic: Fluke 8840A normal behavior??  (Read 872 times)

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Offline PwrElectronicsTopic starter

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Fluke 8840A normal behavior??
« on: May 11, 2020, 02:30:48 pm »
I have this Fluke 8840A that came from the dumpster a few years ago with a tag stating some resistance ranges were out of cal.  I had a prior post about that....

Due to the pandemic, I have been working in my home lab and have been using this meter for DC voltage measurements.  If I measure a voltage, then removed my probes, the meter still shows what I was measuring, but with a very slow "discharge".  If I short the leads together, it will zero or if I move my leads to a different voltage, it follows that.

This is not "normal" compared to other meters I have or ever used in the past.  For example, I also have a Fluke 45 and for my testing, I have been using both meters to measure the same things and the 45 will zero when I remove the leads from my test point.  So do my handheld meters.

Is this normal behavior for this or is something wrong with it and if so, what?

The measurement accuracy seems fine or it agrees with the 45 within 1mV or so, etc.  Just does not zero when leads are floating.
 

Offline hugo

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Re: Fluke 8840A normal behavior??
« Reply #1 on: May 11, 2020, 03:42:03 pm »
This is normal and it is caused by the very high input impedance (10 GΩ in the 0.2, 2, 20 volt ranges)
 

Offline AVGresponding

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Re: Fluke 8840A normal behavior??
« Reply #2 on: May 11, 2020, 04:03:33 pm »
Love my 8840A...

That 10GOhm is a minimum, it may be higher!

These things generally don't drift much unless they get abused with large temperature changes, overloaded inputs etc.

The 8840A has five times the accuracy of the 45, btw...

You can find service manuals for both meters on the elektrotanya website:
https://elektrotanya.com/fluke_8840a_digital_multimeter.pdf/download.html
https://elektrotanya.com/fluke_45_sm.pdf/download.html
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Offline PwrElectronicsTopic starter

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Re: Fluke 8840A normal behavior??
« Reply #3 on: May 11, 2020, 06:54:08 pm »
Thanks  :)

In 30+ yrs in electronics, I have never used a meter that behaved like this so I wondered.

 

Offline DrijSkij

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Re: Fluke 8840A normal behavior??
« Reply #4 on: December 18, 2024, 02:35:49 pm »
Mine does the exact same thing. Good to know.
 


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