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Old 12th Jun 2019, 6:18 pm   #1
Techman
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Default Fluke 8010A digital multimeter

All this bad weather is keeping me in and causing me to start finding faulty items of test gear that have been festering away in cupboards for years, making me have another look at them to see if they're fixable.

I'd forgotten what was originally wrong with this meter until I connected a couple of test leads and attempted to measure the voltage of a 9 volt PP3 battery. It basically just gives random and changing readings around the 35 volt(ish) mark.

Is it worth proceeding with this or has it had it?

At least the display is good and it's possible that it may fit another meter that I've yet to find that's got a bad display, but otherwise was working. I think this other meter may well be a Fluke, although it's badged as some other make, but I can't remember until I find it again.

Photo of meter below:-
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Old 12th Jun 2019, 7:34 pm   #2
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Default Re: Fluke 8010A digital multimeter

....Is it worth doing a live test, ie going around selectively cooling any suspect components with freeze spray to see if ordinary service is resumed?

Dave
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Old 12th Jun 2019, 7:38 pm   #3
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Default Re: Fluke 8010A digital multimeter

Will probably be the power supply capacitors in it. I've seen that a couple of times. They leak electrolyte eventually and cause the metering to go bonkers.

Last one I did had that problem. See top right for the three cretins
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Old 13th Jun 2019, 6:23 am   #4
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Default Re: Fluke 8010A digital multimeter

I've had a similar problem with a another Fluke bench meter, I cleaned the the contacts on the SW's which cured the problem on mine though duff caps might also be involved.

Andy.
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Old 13th Jun 2019, 12:24 pm   #5
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Default Re: Fluke 8010A digital multimeter

Many thanks for the replies and suggestions chaps.

However, MrBungle has pointed me in the right direction.

But look what I found!

Can you spot the 'deliberate' mistake?

Manufacturer error - as you can see by the solder joints, it's been like that from new. If these are made on an assembly line, then it makes you wonder whether there were a whole batch that were faulty from new.

There's a bit more to it regarding this meter and I'll post back later with the full story.
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Old 13th Jun 2019, 1:32 pm   #6
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Default Re: Fluke 8010A digital multimeter

Sabotage! A friday afternoon polarity shift.

The push button selection, to my mind, is a good arrangement..but if the contacts are silver plated like Farnell Bench DMM's of that period they might have blackened and benefit from a clean.

Dave
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Old 13th Jun 2019, 2:04 pm   #7
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Default Re: Fluke 8010A digital multimeter

Quote:
they might have blackened and benefit from a clean
That will be silver sulphide, it is conductive and not a problem in voltage i.e. low current use, that's why it is silver.
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Old 13th Jun 2019, 5:12 pm   #8
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Default Re: Fluke 8010A digital multimeter

That's hilarious. I imagine it probably eventually went short. The meters use so little current and the transformer is rather wimpy so it looks like it just didn't explode.
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Old 13th Jun 2019, 7:31 pm   #9
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Default Re: Fluke 8010A digital multimeter

I think there was about 5 volts across it, whereas there's around 15 volts now I've replaced it. It wasn't quite short circuit, but down to a few K. It had started to bulge and leak at the bottom as can be seen in one of the pictures below.

As shown in the first picture below, when I first opened it up I noticed part of a Post-it note stuck to the board with 'fault' written on it, indicating that it had been looked into before. I would think that it went faulty soon after it was originally put into use and once it started to play up it would have been switched off taken out of service fairly quickly, as I would certainly have expected that capacitor to have gone pop. I don't think this meter has had a lot of use, so I've just replaced the one capacitor and the meter is now working. I think that the person that originally opened it up probably had its chassis on the bench along with others and decided it was not worth repairing, having not noticed the incorrectly fitted capacitor and just boxed it back up for chucking in the skip. It didn't actually get to the skip as I happened to spot the trolley full of scrap gear on its way and was asked if there was anything I wanted and to help myself.

When I put the case back on I noticed a rattle from somewhere, so I removed the case again and traced the rattle to a spring within the milliamp socket. This was because the 2 amp fuse was missing, probably having been removed to replace a blown one in another working meter. I replaced the fuse with a 2 amp quick blow and did a quick check on the 200mA range against an AVO, and it agreed at around 40mA with a 1.5 volt cell and a series resistor, although I haven't as yet done an accurate test against another DVM on any of the current ranges.

I did the test again on the 20 volt range with a PP3, the same as I did originally when the meter was faulty, and as can be seen in the picture, it's now working well reading 9.66 volts. However, it's reading slightly high as this battery reads 9.60 volts on another meter that I regard as accurate. Having just found a copy of the manual on-line, I see that according to page 47, that it might just be within specification at the higher end limit. I haven't at this stage done any more checks, but I feel that it ought to be more accurate than that - any advice on 'adjustments' welcome, although I haven't studied the manual properly yet.
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Old 13th Jun 2019, 7:51 pm   #10
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Default Re: Fluke 8010A digital multimeter

The manual might recommend leaving the meter powered up for 30 minutes to achieve maximum accuracy.

Dave
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Old 13th Jun 2019, 8:17 pm   #11
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Default Re: Fluke 8010A digital multimeter

It just says to allow the instrument to stabilize and perform the test at an ambient temperature of 23 C.

On the 20 volt DC range it says in the chart that a 19.00 volt test voltage is acceptable to have a display reading between 18.97 to 19.03 volts. I'm a bit surprised that this is acceptable, but then it is an early generation meter. I'm sure it's capable of better.

I need to really do some proper checks of all the ranges to see if it's a general inaccuracy over the whole set.

I'm very pleased with the meter and it'll get some proper use on the bench once I'm happy with its accuracy.
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Old 13th Jun 2019, 8:26 pm   #12
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Default Re: Fluke 8010A digital multimeter

Actually, looking again at the specification it is actually out of spec. I'll do the test with a bench supply set to 19 volts and see what we get against another meter, then I'll test all the other ranges as per the charts.
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Old 13th Jun 2019, 10:12 pm   #13
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Default Re: Fluke 8010A digital multimeter

I'd be more inclined to trust the Fluke as having the best absolute accuracy compared to almost any other meter out there. They are quite surprising when it comes to calibration. I've never seen one actually outside cal other than one that got left outside in the rain for a month and all that needed was an isopropyl scrub on the high impedance bits of the PCB.

If you're not sure, I would grab a cheap AD584 voltage reference from ebay or aliexpress. Usually cost 5 to 15 inc delivery depending on where they are arriving from (might take 2-3 weeks from China) and features. All just as good. That'll give you a certain enough for 4.5 digit meters reference to check everything against.
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Old 16th Jun 2019, 8:25 pm   #14
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Default Re: Fluke 8010A digital multimeter

I did the dirty deed and gave it a small adjustment, it can always be re-set again if necessary. Thanks for the tip about the voltage reference sources, I'll get one ordered. The AC voltage ranges are a bit out compared to other meter, particularly on the 750 volt AC range when I measured the mains it seemed to be nearly 5 volts high, but I'll do some more thorough checks against different meters some time when I get round to it.

It is quite a vintage meter. There's a 'C' 1979 on on a stand up board with another date rubber stamped near it of 19th September 1983, so time for it to drift just a little. I also noted that the adjustment preset has a knurled wheel which is quite close to the board edge and it isn't exactly 'tight', so could easily have been moved slightly when handling the board, or even caught on the case ribbing when the board was being removed from the case.

I found the other meter that I mentioned and it wasn't the one (or the make) that I thought it was, so perhaps there's even another faulty one somewhere yet to find. The one I've uncovered is a Soar 5030 and at first it seemed that the display needed pressing to get it to display anything, but after a while it seemed to recover. It seems to read nearly a volt high and there doesn't seem to be any information available out there to clarify which adjustment is which. The only preset labeled is on a small sub board and is for AC volts. I seem to think that I have the original instruction book for this meter somewhere filed away, but from memory I seem to think that it was a very small book with little information in it, but I'll have to look it out and see what it says.

Do you, or anyone else know if this meter is a re-badged Fluke?
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Old 16th Jun 2019, 10:12 pm   #15
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Default Re: Fluke 8010A digital multimeter

I do have an AD584 which seems ok, i previously relied on an 'Adafruit' Vref supplied by Pimoroni (from UK stock) which is on a breakout board about the size of a micro SD card. You do have the job of wiring it in to an appropriate project box though. It was about 7 and produces 2.048v or 4.096v from a PP3.

When calibrating ACV on a couple of meters i started off using an inverter generator's offload 230v sinewave, on the basis that the processed output should be quite precise. I checked the output with a pair of Avo Model 9/II meters, which read 229.5v and < 231v. On this basis (and on the balance of probabilities) i took this as a 230vAC reference for checking a couple of DMM's- both of which needed adjustment- and not just by 1 volt, i might add.

Dave
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Old 18th Jun 2019, 9:24 pm   #16
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Default Re: Fluke 8010A digital multimeter

Cheers for all the advice and comments. The switches on this meter seem to be perfect and didn't need any cleaning, as I said before, I suspect that this meter failed early on in its life due to the incorrectly fitted capacitor, so hasn't had a lot of use to wear them out. I had to take it out of its case again to slightly readjust the DC voltage ranges - I think that pot is a little loose in its action and could really do with replacing to make it perfect.

I realised that the AC voltage adjustment is a bit more involved with the two adjusting pots interacting with one another, also there's low frequency and high frequency adjustments for this. I verified the approximate AC calibration of the DVM being used to calibrate against by comparison with a good analogue meter that I know is right and decided to adjust the AC voltage ranges at the low frequency settings using the mains as opposed to 100Hz as specified. The calibration voltages are, as they are in the DC adjustments, 1.90 volts and 190.0 volts. I'd forgotten how 'old school' these early DVMs are in that they're not linear. When set correctly at the top end of the range, they're then slightly out lower down in the range, and it's the same on both AC and DC ranges and there's only a single adjustment on DC, so just like a good old AVO then! However, this is good enough for most bench use.

As regards to the other meter that I mentioned, I found the original owners instruction manual for it. After looking through several drawers, I found it sandwiched in between a mig welder and a trolley jack manual - exactly where you'd expect it to be then! It's a better manual than I'd remembered and contains a circuit diagram and a parts list, but no information on calibration, so that'll involve a bit of guesswork. However, it didn't get that far as the meter went completely haywire after it had been switched on for a short while, so I've put it to one side for the time being and may start another thread regarding its possible fixing, that's if I think it's worth the trouble. Looking more closely at it and its manual, I've decided that it doesn't have any connection with Fluke after all, although it dates from around the same time as the Fluke meter under discussion in this thread.

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Old 18th Jun 2019, 10:00 pm   #17
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Default Re: Fluke 8010A digital multimeter

Watch out for the 8010A's AC range. It's a "true RMS" meter so unless it's from an AC calibration source it won't read the same as an averaging meter i.e cheap DMM or Avo.

The other one is actually a nice little meter. It's made by Soar corporation who were a semi respectable manufacturer in Japan back in the 80s. Similar to GW Instek in modern test gear ranking.
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Old 18th Jun 2019, 10:02 pm   #18
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Default Re: Fluke 8010A digital multimeter

Perhaps you have another capacitor problem..!

I (almost) mentioned non-linearity in Post No.15- my Farnell DM131 must be around 1977 vintage, and although i haven't done a thorough calibration on it, the ACV ranges are such that having it correct at 240vAC means it is no longer accurate at 15vAC. It's useful though for me to have a bench meter with a large hi-viz LED readout and high impedance.

Dave
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Old 18th Jun 2019, 10:10 pm   #19
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Default Re: Fluke 8010A digital multimeter

That's pretty normal.

Just remember that the mains isn't a usually a sine wave. Your 15V AC sine wave is probably more like a real one if it's out of a function generator.

A lot of the converters on older DMMs, DM131 are just an opamp "ideal rectifier" to get a peak reading and then an amplifier with a gain of 0.707 scaling down to the FSD of 200mv.

8010A has a proper RMS converter which does a pretty precise integration. My decent HP 34401A reads bang on the same as the 87V and 8012A on the mains but the cheaper Tenma and older 8000A are completely different.
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Old 19th Jun 2019, 10:01 am   #20
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Default Re: Fluke 8010A digital multimeter

I also have a DM141 which claims true RMS (and also has an extra digit) but the rotary switch contacts are not too robust looking. The Fluke push-buttons look a much better idea for durability. (especially as they probably have zero wear..)

Dave
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