Author Topic: Fluke 115 and Nanofarad Capacitance Readings  (Read 4858 times)

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Online bdunham7

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #25 on: April 18, 2023, 08:27:08 pm »
For those of you who were kind enough to test read some caps and reported success with your meters in the nF range, how long were the test leads you used? I'm thinking the shorter the better. I think I'm going to put something together with two banana plugs and a spare header connector so I can have a 'plugin test port' for these things with NO test lead length to worry about.

I tried my F116, which should yield the same results, using the TL175 leads and insulated alligator clips that came with the meter.   I got exactly 220nF with my .22µF 'standard' and 7nF with a 6800pF mylar, so all within 1 count.  Moving the leads around and even putting 1A @ 1kHz through a cable wrapped around one test lead 5X only resulted in a few counts of deviation.  So either you have some industrial-grade interference at your location or something else is going on. 

Are your leads twisted together or touching or something?  I took no special precautions with mine.  Did you try measuring DCR?  Also, when you are turning the meter on, are you holding down any buttons, such as to defeat the power-off or backlight-off functions?
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline tautech

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #26 on: April 18, 2023, 09:01:15 pm »
And I have discovered the problem. It's not the meter but its test leads. It's like they are acting as additional storage capacity and making the the smaller caps look larger than they really are. If I dispense with the leads entirely and insert the cap leads into the meter's test lead sockets then everything reads as it should. The Radio Shack 22-181 I have has a dedicated Cap/Resistor test port so that's why it was reading OK - no test leads involved with it.

The test leads that came with the 115 are 55 Inches long so I guess that's a lot of insulated copper when you think about it. I cobbled together a 4 Inch long set and Voila, the meter reads nF caps as spec'ed. I am a happy camper once again!

For those of you who were kind enough to test read some caps and reported success with your meters in the nF range, how long were the test leads you used? I'm thinking the shorter the better. I think I'm going to put something together with two banana plugs and a spare header connector so I can have a 'plugin test port' for these things with NO test lead length to worry about.

Thanks to everyone who assisted on this as it was driving me nuts! I just couldn't believe such a meter would have a problem like that. I feel bad about turning one in but at least I had my epiphany before I returned the second one. Now what to tell the wife about the third one that arrives tomorrow...  :-//
 
Barry
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Welcome to the world where precise measurements are a science on their own !

However those of us with a few years under the belt will have seen many a twisted wire trimmer in a circuit used as some final trimming/tuning.
To the observant, long lead effects on measurements are just normal.  ;)
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Some stuff seen @ Siglent HQ cannot be shared.
 

Offline Barry A. WatersTopic starter

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #27 on: April 18, 2023, 10:58:50 pm »
I tried my F116, which should yield the same results, using the TL175 leads and insulated alligator clips that came with the meter.   I got exactly 220nF with my .22µF 'standard' and 7nF with a 6800pF mylar, so all within 1 count.  Moving the leads around and even putting 1A @ 1kHz through a cable wrapped around one test lead 5X only resulted in a few counts of deviation. So either you have some industrial-grade interference at your location or something else is going on. 

I can't speak to your success with the TL175 Test Leads as that is an upgrade from the Test Leads that currently come standard with a new Fluke 115. Perhaps you could repeat your test with the lesser quality Test Leads the 115 comes with?

Barry 
« Last Edit: April 18, 2023, 11:01:02 pm by Barry A. Waters »
 

Online bdunham7

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #28 on: April 18, 2023, 11:20:02 pm »
I can't speak to your success with the TL175 Test Leads as that is an upgrade from the Test Leads that currently come standard with a new Fluke 115. Perhaps you could repeat your test with the lesser quality Test Leads the 115 comes with?

Which ones are they?  The TL75 with plain red and black probes?  And were you using the slip-on alligator clips or something else?

I'll try the TL75 before I finish this post....

...and I'm back, no change using TL75 and the older Fluke alligator slip-ons.

I keep begging you to measure DCR, and if you do also try measuring the DCR of the leads when shorted together.  I had a strange problem recently with older but unused Fluke leads (TL71 IIRC) where there was a tarnish or something on the probe tips that had to be polished off--isopropyl didn't help--and I think it may have been outgassed stuff from the silicone leads.  I was getting strange DCR readings up to 30R when shorting the leads, after polishing with "Barkeepers Friend" I now have 0.2R pretty reliably.  I'm not saying that's your issue, but if using your own custom leads fixes the problem entirely I don't know how it could be anything else.  It certainly isn't a natural characteristic of test leads, especially not in the 100nF region.  5-10pF, perhaps, but these meters and their measuring method doesn't get near those values.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline Barry A. WatersTopic starter

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #29 on: April 19, 2023, 01:52:02 pm »
Are your leads twisted together or touching or something? ...

Yes... ME! And THAT was my issue. Thank you for not giving up on me bdunham7, even when I thought I had found my problem. As you and gamalot have pointed out, the Test Lead length of 55" is common and should not be the problem, and it wasn't (I have added a note to this effect in my post stating the leads were to blame above).

I was holding each lead of the capacitor in contact with its test lead with thumb and forefinger for lack of suitable alligator clips. I now assume I was measuring the capacitance of the capacitor AND the human tissue surrounding the contacts. The electrolytics measured OK because my fingers only threw things off +/- 1 uF, not really enough to notice. With nF stuff it was MORE than enough to notice, hence my dismay.

What a stupid problem to have  :palm: Please feel free to tell me so!  :-DD

Barry
(Who now has a fresh pair of mini-alligator clips) 
 
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Offline BeBuLamar

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #30 on: April 20, 2023, 02:44:03 pm »
Now you sucessfully get Fluke to destroy 2 perfectly good meters.
 

Offline Barry A. WatersTopic starter

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #31 on: April 20, 2023, 09:12:41 pm »
Now you sucessfully get Fluke to destroy 2 perfectly good meters.

And how would that be so?

Barry
 

Offline BeBuLamar

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #32 on: April 20, 2023, 10:36:52 pm »
If you returned them and they accepted them they are going to destroy the ones you sent back.
 

Offline Barry A. WatersTopic starter

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #33 on: April 21, 2023, 01:41:07 pm »
If you returned them and they accepted them they are going to destroy the ones you sent back.

But the scenario that you portray above and which so disturbs you is not what happened.

Barry
 

Offline BeBuLamar

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #34 on: April 22, 2023, 12:01:45 pm »
So you didn't return the meter?
 

Offline Barry A. WatersTopic starter

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #35 on: April 22, 2023, 01:14:33 pm »
So you didn't return the meter?

If you were to read my posts above you may gain a better understanding of what transpired.

Barry
 

Offline BeBuLamar

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #36 on: April 22, 2023, 03:50:29 pm »
I read that you brought the meter back and they replaced it in the first post. In another post you said the second meter is packed for return and no accessible. To my best understanding you returned 2 meters. Isn't that so?
 

Offline Barry A. WatersTopic starter

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #37 on: April 25, 2023, 12:24:06 pm »
... To my best understanding you returned 2 meters. Isn't that so?

No. I  would suggest you slow the speed of your reading and place more emphasis on comprehension.

Barry
 

Offline 4thDoctorWhoFan

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #38 on: April 25, 2023, 12:50:55 pm »
... To my best understanding you returned 2 meters. Isn't that so?

No. I  would suggest you slow the speed of your reading and place more emphasis on comprehension.

Barry
I would have to agree with BeBuLamar.

In reply#7, you stated:  "it sounds like my experience is the odd man out so back the meter goes (for the second and final time!). I ordered another 115 from a totally different supplier in another state to insure I don't get one from the same batch as the two I've had. We'll see how that goes.

So what that you went through 2 meters because of operator error.  It's no big deal.

« Last Edit: April 25, 2023, 12:53:13 pm by 4thDoctorWhoFan »
 
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Offline Swainster

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #39 on: April 25, 2023, 01:39:08 pm »
I think the point of contention is that the meters had been destroyed. While its not impossible, i personally doubt it as Fluke Service will probably run the meter through the official performance test before destroying them. I think it's been established that they would have passed this test.
 
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Offline Barry A. WatersTopic starter

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Re: Fluke 115 and Nanofarad Capacitance Readings
« Reply #40 on: April 25, 2023, 04:56:32 pm »
I heartedly agree with Swainster and 4thDoctorWhoFan (Tom Baker is the only REAL Dr. Who!) but what Mr. BeBuLamar keeps repeatedly missing is the statement below in Reply #22:

... Thanks to everyone who assisted on this as it was driving me nuts! I just couldn't believe such a meter would have a problem like that. I feel bad about turning one in but at least I had my epiphany before I returned the second one. Now what to tell the wife about the third one that arrives tomorrow...  :-//

When the 2nd meter was repackaged for return two other posts convinced me to reopen it and keep digging. That process left me thinking that additional capacitance in the leads was to blame (incorrect) but that the 2nd meter (as well as the 1st) was fine (correct).

I'm a person that believes if someone is going to lay blame for something on someone's doorstep it is best that they know what they are talking about. Mr. BebuLamar did that and after repeated attempts could STILL not correctly determine that only 1 meter was returned. That it was returned under advisement from a fluke Tech Support person seems to also have escaped Mr. BeBuLarmar's attention.

Why he is so concerned over the fate of a low-end consumer piece of equipment I do not know. Fluke is capitalized at somewhere over $25B and if they destroy returned items that's their way of saying "We don't care one iota about that. It's not economical for us to do anything else with it.".  Maybe he will call them and get them to change their destruction policy (if they indeed have one).

He may also wish to call Lowes and inquire about their policy regarding returned items because that is where the one meter that was returned went. Unfortunately, I don't think Lowes cares much about it either. (Entertaining Bonus Material Coming Up!)  :)

When I returned the ONE and ONLY meter the person at the Returns Desk said they couldn't do an exchange but had to issue a Credit and then re-Debit the amount on the card that was used originally. OK, net zero so no problem but the guy seemed confused about how to do it. Ultimately he got me another meter and off I went. A few days later I noticed the Credit at the bank but no subsequent Debit. A quick perusal of the return receipt backed this up. Credit issued but no Debit.

I called the store and sure enough things were amiss. The guy should have scanned and Debited the replacement meter before I left. The guy I spoke with asked if I could come in with the packaging but I don't live in the town where it was bought and only go there every now and then. They also could NOT take payment via Credit Card over the phone (company policy) so what does the guy say? Don't worry about it. Keep it!  :o

Tempted? For about 10 seconds BUT you can't go through life like that as Karma will get you SO I was able to drop in today and pay. The person at the desk looked at me like I was stupid for returning to pay for it since I'd gotten away clean and I feel the guy that told me to keep it did so only because it was a hassle and he didn't want to deal with it. Go figure!  :-//

Barry
« Last Edit: April 25, 2023, 09:14:15 pm by Barry A. Waters »
 
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