Author Topic: Purchased used Fluke 289 - need some advice  (Read 496 times)

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Offline m3jala

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Purchased used Fluke 289 - need some advice
« on: March 21, 2019, 09:03:03 am »
Hi all -

I picked up a used Fluke 289 recently and in inspecting it feel that something is wrong with it.

Having no leads plugged into it, when I set it into mVAC mode, the meter does not even out to 0. It hovers around 5.2 mVAC, putting it into regular VAC mode (again the leads are not connected), it settles to about 0.0315 VAC.

Both DC and mDC settle to around 0.

For anyone with experience with this, is this a faulty meter?

Thank you.
J
 

Online 0culus

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Re: Purchased used Fluke 289 - need some advice
« Reply #1 on: March 21, 2019, 09:11:28 am »
If you short the leads together, it should drop to zero. Basically, the leads will act like antennas and pick up local EMI.
 

Offline m3jala

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Re: Purchased used Fluke 289 - need some advice
« Reply #2 on: March 21, 2019, 09:21:38 am »
Thank you - I appreciate the response. I'm not seeing it go to 0, see these photos. This isn't normal right?
 

Online 0culus

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Re: Purchased used Fluke 289 - need some advice
« Reply #3 on: March 21, 2019, 09:31:19 am »
I think it's fine. My 87-V does about the same thing when you short the leads out like that. Goes down to 0.2 mVac and stays there.
 

Online helius

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Re: Purchased used Fluke 289 - need some advice
« Reply #4 on: March 21, 2019, 09:32:54 am »
There are low-frequency electric fields in most places, unless inside a Faraday cage or deep in the woods. The loop enclosed by your leads is enough to pick them up in AC mode (no surprise that they do not register in DC mode). Try putting a shorting bar in the jacks instead of the leads, the much smaller loop area will register as a much lower AC voltage.

If you turn on frequency display, you'll probably see a big fat "60.000 Hz" and understand where that reading is coming from.
« Last Edit: March 21, 2019, 09:34:34 am by helius »
 

Offline commongrounder

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Re: Purchased used Fluke 289 - need some advice
« Reply #5 on: March 21, 2019, 09:33:39 am »
From the 289 manual:

True-rms:
AC mV, AC V, AC μA, AC mA, and AC A specifications are ac-coupled, true rms, and are specified from 2 % of range to 100 % of range, except 10 A range is specified from 10 % to 100 % of range.

AC Floor:
When the input leads are shorted together in the ac functions, the Meter may display a residual reading up to 200 counts. A 200 count residual reading will cause only a 20 count change for readings at 2 % of range. Using REL to offset this reading may produce a much larger constant error in later measurements.
 
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Online rsjsouza

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Re: Purchased used Fluke 289 - need some advice
« Reply #6 on: March 21, 2019, 09:34:26 am »
Are the probes shorted in your third photo?

If so, keep in mind the meter is measuring 300µV, which is well within the noise margin of lots of True RMS converters.

In this case, can you try to clean the probes thoroughly and rotate its banana jacks? Given the magnitude of the error, I wouldn't be surprised if grease is the culprit here.
« Last Edit: March 22, 2019, 12:28:26 am by rsjsouza »
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Online 0culus

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Re: Purchased used Fluke 289 - need some advice
« Reply #7 on: March 21, 2019, 09:38:51 am »
Yep, it's almost certainly 60 hz hum you're seeing. If you have an oscilloscope you will see it there as well, from a non grounded probe.
 

Offline mr.fabe

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Re: Purchased used Fluke 289 - need some advice
« Reply #8 on: March 21, 2019, 09:41:25 am »
I just checked my 289 and it exhibits similar readings.  My unit was recently repaired with a new board swap and calibration.

You may want to check your FW version, check the super cap and also do a low ohms test.  Put your unit in Low Ohms mode, short your leads and if the display starts to fade, your unit is defective.
« Last Edit: March 21, 2019, 09:47:13 am by mr.fabe »
 

Offline m3jala

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Re: Purchased used Fluke 289 - need some advice
« Reply #9 on: March 21, 2019, 10:23:53 am »
Thanks all, I appreciate all your responses.

Mr. Fabe - I'm on an old FW version (1.0) with calibration from '07. Already checked the supercap, appears fine. Just ran the low ohms mode you mentioned, no fading.

When nothing is plugged in, I read 170 hz and 4.375 mVAC.

When I put a shorting bar (a paperclip) into the jacks, I read 0hz and 0.281 mVAC.

I'm in a townhouse area with a ton of power lines, computers, wifi and neighbors, so sounds about right for the background noise assessment?

Thanks much all.
 

Online 0culus

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Re: Purchased used Fluke 289 - need some advice
« Reply #10 on: March 21, 2019, 10:25:33 am »
Yep that sounds about right. I only see 60 Hz where I am, but my neighbors are not packed in either!
 

Offline m3jala

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Re: Purchased used Fluke 289 - need some advice
« Reply #11 on: March 21, 2019, 10:29:53 am »
Perfect, off to kick off some projects with my new to me 289 in that case! Thank you.
 

Online 0culus

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Re: Purchased used Fluke 289 - need some advice
« Reply #12 on: March 21, 2019, 10:41:54 am »
No problem! BTW, welcome to the forum! Visit us in Test Equipment Anonymous if you're into test gear.  :-DMM  :-DD
 

Offline m3jala

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Re: Purchased used Fluke 289 - need some advice
« Reply #13 on: March 21, 2019, 01:14:10 pm »
I'm definitely easing into it. I have to say, can already tell this is a great board with all the awesome responses.

I come here on a couple car projects of mine that require electrical work. Figured I'd teach myself the trade while at it :box:

Take care and see you around.
 
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Offline mr.fabe

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Re: Purchased used Fluke 289 - need some advice
« Reply #14 on: March 21, 2019, 03:34:54 pm »
You may want to consider upgrading your firmware or use electrical tape on your optical sensor on top of your unit.  The current firmware available for the 289 is v1.16.

From the Fluke website...

Version 1.16 corrects an issue where recording sessions could be interrupted or terminated when using the record function in combination with ambient conditions of bright sunlight or other sources of bright light, when used without the IR cable attached. Version 1.16 does not apply for units labeled 287/TPWS or 287/NUC

If you feel the need to update your firmware, you should contact Fluke technical support to make sure calibration is not required after updating your unit.  Version 1.0 is pretty old...
 

Offline m3jala

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Re: Purchased used Fluke 289 - need some advice
« Reply #15 on: March 22, 2019, 12:21:27 am »
Yes, thank you I saw that.
 

Offline agdr

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Re: Purchased used Fluke 289 - need some advice
« Reply #16 on: March 23, 2019, 09:39:07 pm »

Having no leads plugged into it, when I set it into mVAC mode, the meter does not even out to 0. It hovers around 5.2 mVAC, putting it into regular VAC mode (again the leads are not connected), it settles to about 0.0315 VAC.

Both DC and mDC settle to around 0.


I also just received two 289's back from Fluke for repair (supercaps) and calibration a couple of weeks ago.  They do exactly the same.  Looks like Fluke did board swaps with recent (mfg date 2 years ago) boards in both.
« Last Edit: March 23, 2019, 09:44:30 pm by agdr »
 


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