EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: smni on March 13, 2014, 06:20:12 am
-
I've been using a cheap multimeter for some time now and it hasn't given me any issues: http://www.amazon.com/INNOVA-3320-Auto-Ranging-Digital-Multimeter/dp/B000EVYGZA/ (http://www.amazon.com/INNOVA-3320-Auto-Ranging-Digital-Multimeter/dp/B000EVYGZA/)
However, I decided it's time to get a little more serious and get something with a little more accuracy and speed for hobby electronics / microcontroller type projects. I also wanted max/min/average capability which the cheapo doesn't have.
After watching hours of multimeter reviews on YouTube and reading lots of forums, I finally decided to take the plunge and get a Fluke 87V. I didn't feel like I should spend that much, but after lots of reviews I decided I would just go for it and hopefully it would last me for many years. I bought it used on eBay and hoped for the best.
I just got it today and it seems to be operating somewhat normally (looks like it was treated well, accesses all the functions, gives readings for current, resistance, capacitance, etc), but I'm not sure what to make of the resistance measurements. I have been checking several resistors, and I'm afraid that the cheapo INNOVA multimeter is making more sense than the Fluke.
First of all, when turning on to resistance mode, it reads 44.15 M ohms with no leads attached in auto range (60 MOhm range). I think this is a big red flag, as I think it should read OL. However, manually changing the range to anything other than 60 MOhm does read "OL".
Here's what I'm coming up with with in measuring the same resistors side-by-side in auto range mode:
47 ohm, 2%
INNOVA: 47.0
Fluke: 47.0
4.7k ohm, 2%
INNOVA: 4.69 k
Fluke: 4.683 k
1M ohm, 2%
INNOVA: 0.981 M
Fluke: 0.960 M
10M ohm, 5%
INNOVA: 10.03 M
Fluke: 8.19 M
So that's what I've got. Any thought on what might be the issue with the Fluke? Should I try to return it to the eBay seller or is there something I might be able to fix/replace myself relatively easily?
Thanks for the help!
-
You should test it on DC voltage first, to see if it in spec. Of course, you will need a pretty reliable voltage reference to draw any conclusion.
It might need a calibration, if it hasn't had one for a few years.
-
It looks like you have leakage on the input.
Lets assume that without any test leads the leakage is 44.15M
When you are measuring the 10M you potentially have 44M in parallel.
Do the calculations and you get around 8.15M - agrees with your results.
I suspect faulty input - possibly water/dirt ingress.
Open up and look to see for water marks or oil / dirt.
( the results you see are way beyond calibration issues - its a fault )
And let us know how you get on :-)
-
OK, well not ultra precision voltage regulators, but I measured both 5 and 3v3 from an arduino uno, powered by a 12V wall wart:
3v3
INNOVA: 3.30
Fluke: 3.305
5v
INNOVA: 5.00
Fluke: 5.006
Vin
INNOVA: 11.51
Fluke: 11.503
-
It looks like you have leakage on the input.
Lets assume that without any test leads the leakage is 44.15M
When you are measuring the 10M you potentially have 44M in parallel.
Do the calculations and you get around 8.15M - agrees with your results.
I suspect faulty input - possibly water/dirt ingress.
Open up and look to see for water marks or oil / dirt.
( the results you see are way beyond calibration issues - its a fault )
And let us know how you get on :-)
Andy, that's exactly the type of feedback I was hoping for, and backed up by math even! Seems like a good explanation
Its getting late here and I have to work in the morning, so I'll take it apart and have a look tomorrow. Will report back with my findings.
-
First of all, when turning on to resistance mode, it reads 44.15 M ohms with no leads attached in auto range (60 MOhm range). I think this is a big red flag, as I think it should read OL.
You are correct, it is a big red flag. With no leads attached, it should definitely read 0L.
If you post a link to your auction, we can see if the seller is someone who knows multimeters or a potential scammer.
Should I try to return it to the eBay seller or is there something I might be able to fix/replace myself relatively easily?
My guess is that your something with your input protection might be bad? Here are the typical things to test as I wrote in another thread ...
https://www.eevblog.com/forum/testgear/fluke-87-v-mystery-low-impedance-input/msg294756/#msg294756 (https://www.eevblog.com/forum/testgear/fluke-87-v-mystery-low-impedance-input/msg294756/#msg294756)
-
I'm going to second what Mr Tiredcaps has to say. No way the thing should read anything but OL when you have no input connected in resistance mode. With the help I got from the other thread I was able to fix that meter. The hard part was dealing with what appear to be Fluke specific MOVs. I ended up swapping parts with a different meter because the replacements I bought from... digikey I think... fit easily in the other meter but not in the 87. Anyway, the upside is failure such as what you are describing seem to be relatively easy to fix with the help of the people here. That doesn't mean you shouldn't tell the seller to either give you a big discount or take the meter back. It's clearly broken as is and unless it was advertised as broken you shouldn't have to pay for it.
-
Thanks for all the info and suggestions! I asked for a return/refund and they said OK so I decided to go that route.
Now it's time to keep an eye out for another good deal. Maybe this time I'll look for one locally where I can bring a few resistors to check it out in person before I hand the money over :-DMM
-
I asked for a return/refund and they said OK so I decided to go that route.
Assuming you are in the USA and it didn't cost too much to return with a tracking number, that is probably your best bet. Meters that are abused/dropped, subject to possibly high voltage, could have other problems.
-
I guess it would be nice to know the seller to warn other potential buyers in case this fluke is re-listed and working.
-
I guess it would be nice to know the seller to warn other potential buyers in case this fluke is re-listed and working.
Yep, which is why I asked for the link to the original auction.
-
I also just bought and received two days ago a 87 V from eBay.
Luckily the only thing wrong was a almost dead 9v battery (reading 6.5v on my old DMM).
The Fluke sure beats using my old BK Precision Dynascan 2845 that uses the 40 pin chip copied from Fluke.
-
Here's the eBay listing for those interested:
http://www.ebay.com/itm/351011237421 (http://www.ebay.com/itm/351011237421)
Seems like a good seller, with only 1 negative feedback out of 1300+ in the last year. And they were very accommodating with accepting my return when I told them it wasn't functioning properly.
And as luck would have it, a Fluke 87V popped up on Craigslist nearby for $150 including probes and case, so I snatched that one up and it works great!
-
Seems like a good seller, with only 1 negative feedback out of 1300+ in the last year. And they were very accommodating with accepting my return when I told them it wasn't functioning properly.
I would give the seller the benefit of the doubt.
And as luck would have it, a Fluke 87V popped up on Craigslist nearby for $150 including probes and case, so I snatched that one up and it works great!
That is good fortune.