EEVblog #372 - Fluke 27 Multimeter Review & Teardown

hi it's retro product review and teardown time and today I've got the classic fluke 27 multimeter here it is great eBay score I picked it up for 40 US dollars practically brand new buy it now can you believe it in Tim right I'll buy it now for 40 bucks I love this meter it is a classic fluke meter it's been around for decades it is their original super rugged waterproof multimeter drop proof 3 meters drop proof waterproof divider though a meter or more just like the fluke 28 series to which you've seen me torture test and flick was still selling this puppy for many decades right up until they release the superseded model the 228 series - this is the fluke 27 it's also available as the fluke 25 there's just some functionality differences it's only got two buttons instead of four so the fluke 27 is the one to go for and it's available in several variants and different colors this is the latest model which is cat 3 input rated it's because this thing was designed before their well this model was designed before the cat standards were even thought of and came around so this new model with the yellow case in plus the charcoal fascia panel on it this is the latest model which I believe is the cat 3 rated model if you get just the yellow one or just the complete charcoal color one that's the older model and you'll find that doesn't have cat 3 radians now I'm not sure if they've actually changed the circuitry in there or they've just rear aided it and rebranded it tested it and rebranded it as the cat 3 but this is a really great meter to pick up on eBay why because it's not only super rugged and it's a fluke but it's also pretty damn accurate as well it's only a 3,200 count so basically our three and a half digit multimeter but it's got not 0.1 percent accuracy normally a three and a half digit meter you know 3200 4000 count whatever you're only going to get point five or point three or maybe point two if you're lucky this one's got point one percent DC volts plus one count so there's not much play in that final digit there at all it's a pretty darn accurate meter and it'll last you a lifetime and yes it does have a lifetime warranty there it is terrific so let's take a look at it do a very quick summary review and teardown hmm love it now the first thing you notice about this meter is that it is big and here it is compared to the 87 v which is already a pretty decently big multimeter as multimeters go it's but technically it's probably just a fraction longer and the same width and it is well basically bigger then it's a the 28 2 which is its new counterpart so a bit of course this one's got Polster of course this one does not come with the rubber holster and it's still rated for three meters drop can you believe it because fluke famously claimed that at container that has plastic twice as thick as their regular multimeters and impact resistant polymer plastic in them so a really SuperDuper rugged meter and the other thing you notice is that it's bloody heavy that's about three-quarters of a kilo let's get the scales out here give the 87 five ago its smidge under 600 grams there and what does this suck away 673 so it's heavier and it doesn't even have a holster hence all that thick plastic and there's probably a lot of metal in these things too because they are very immune to external EMI and let's have a look at there there you go it's basically the same as the new 28 to so it is a big chunky meter but I just love it and the tilting bail on it you can see here it is really quite remarkable it's huge and wide I absolutely love the thing there's no way this sucker is going to fall over when you're using it beautiful and on the bottom of it here we've got some nice rubber strips down here to stop it moving around your bench really quite nice I like it and we have a removable battery compartment this is technically the Fluke 27 /fm now this is an interesting our variant you'll see this sometimes it's written on the front of the meter here sometimes it's branded fluke 27 /fm there and I believe what FM is is it stands for for military in other words it was a specific model they they released for the military I believe it's an absolutely identical meter in every respect and as for the front panel of course this is the new charcoal and yellow model so it is cat 3 specifically cat 3 input rated 10 amp Jack's 32 hundred milliamps and volts ohms and diode jack with standard spacings and shrouded of course and the range switch itself though I really love the range switch on this thing not only does it feel absolutely beautiful and it's designed to use with big gloves on and things like that so you can easily switch it but what I love is that it's basically split down the middle there's two off positions there and but this half is basically all AC so you got volts AC millivolts milliamps amps and micro amps and ohms happens to be on this side because well it's got to be somewhere so basically you switch it in this direction you know you're getting DC none of this pressing button to change to AC and DC mode crap I love it you just move it all on one side or all on the other functionality-wise it doesn't have a huge amount unfortunately it's just got standard min/max the Fluke touch hold the relative mode and the range hold but there's no capacitance capacitance wasn't around on multimeters when this thing was designed and released but it done it does have a fast updating Biograph display down to a couple hundred microseconds or something like that so really super quick bar graph but if you just want a super reliable super rug a multimeter just to measure your traditional volts ohms and amps this one's hard to beat and on the ohms range here even though it's not written there it does have conductance or nano Siemens range you just hold down the right and just press the range button twice and it puts it into now no Siemens great for measuring leakage and stuff like that now there is a bit of a delay when you turn the thing on there there you go it's a bit disconcerting at first you think I'll run out of battery but no trust it it'll eventually turn on and the display is even though the digits aren't very large the contrast is actually very very nice from pretty much any angle so there it is side by side with a fluke 87 and as you can see at this particular angle the contrast is much better on the old fluke 27 but there's no backlight capability at all just be aware of that and from the opposite angle it still beats it let's check inside the battery and fuse compartment metal threaded inserts on all four screws lovely and it just lifts up completely oh ring seal because this thing is waterproof dustproof oil proof everything proof I love it and you know and there's nothing fancy here at all it's just a loose 9-volt battery but it does have the foam on the bottom to keep it in place so it seems to work reasonably well yeah it's just your traditional battery snap but they've got the spaghetti or is that heatsink that looks like no I sort of not really heat shrink tubing is like rubber tubing or something like that it feels feels very rubbery anyway they have done that to protect the wires so then they get pinched and stuff like that and if we take that out and get in here today we can get access to the two hrc fuses and they're 440 milliamps and 11 amp fuses for the two ranges and the nice little fuse cover there stops them from coming in the front you know vibrating out popping out and coming loose I like it but probably the thing that most impresses me about this meter is the battery life from a standard 9-volt battery it has got a rated 1000 hours battery life yes folks four digits can you believe it ha it's a stuff of wet dreams really in a multimeter beautiful I don't know another multimeter on the market that matches this thing and this thing is what upwards of 20 years old now unfortunately there are a couple of more downsides to the meter the diode range only goes to two volts maximum so you can't test white LEDs with it and the continuity buzzer unfortunately the bar graph is going there but it takes some time so it doesn't even pass the slow scan probe test look at that right it takes some time unfortunately but it is fully latching and well I did get this thing on eBay so have I bought a dud let's check out the resistance range first I've got my resistance standard here point double O 5% 10k bang 10k you better believe it haha let's try 1k and see what we get yeah spot-on and let's try my EDC MV 106 voltage standard this is a 3200 count meter so let's put it on 3.0 volt shall we and let's give it a go spot practically swimbot on there we go three point zero and two one no drama whatsoever let's take it all the way up to ten not a problem and let's take it to 300 millivolts ah look at that least significant digit nothing doing there spot-on absolutely spot-on fantastic winning score on eBay beauty and I use my Keithley two t5 currant sauce that should be a hundred milliamps and it's close enough well within spec well within spec ten milliamps yep spot-on let's go down to a hundred micro amps no sorry one that's that's one milliamp there we go ninety nine eight beautiful certainly close enough let's go down to 100 yep spot-on ten micro amps beauty just another thing it doesn't have no input jack alert for amps not that fancy modern stuff Blair warranty void if seal broken screw that and the screws in this thing appear to not fall out when you unscrew them but they do eventually pull out and yes they are there is no metal threaded inserts for these ones but you should never have to open the case on this there's rubber o-ring grommets down in there so just be careful of those if you want to maintain the waterproofness of this thing you have to be extremely careful what you're doing so let's crack this puppy open and what is our ring yeah whoops just be careful of that but look at all that shielding you'll notice the fairly deep ridges around there that go right into the top part of the case there and there's good blast protection there soft this thing goes kaboom inside it's not going to escape very easily with those high walls and the o-ring very safe meter and the input jacks here a solid metal posts with shake proof washers under there and screwed directly into the PCB but the fuse PCB as you can see is on that vertical riser board down in there which is soldered directly onto the board so the board is got these cutouts in them like little tabs which then feed through the main PCB here and then they're soldered directly onto the board it's rather novel and as you'd expect on a fluke the soldering quality is absolutely first-class on that riser board but I guess the only issue with that riser board is that it could potentially are those shots solder joints could potentially crack with them when you insert and remove those fuses because all the pressure and the flex on the board but I think they've done their homework on that and it's going to be rigidly held in place so that shouldn't be an issue and you'll notice on the side here how it's also shielded but then there's a breaks in the shield therefore all the calibration trim pot adjustments love it and one of the big features of this meter is it's very high electromagnetic immunity hence all the shielding and everything else around it is really a very nicely shielded unit so let's pop that off and it's not easy to take this thing apart look so we're going to take the jacks out to get the whole board out it's a multi-step process to take this apart hence having the adjustments on the side there so you can adjust and Cal this thing without having to tighten to disassemble the whole down lot and the funny thing is even when you take these screws out on top of the shield you can't get it out because there's actually an embedded threaded nut in the shield itself there's two of them embedded in there which are unscrew from the bottom so I'm going to take this whole unit out before I can even get that done shield off and one interesting thing to know is that there is a bit of wiring on these input jacks I mean this Jack absolutely goes nowhere it's got no components or anything on the bottom but it's got that wire flowing off down further into the board and likewise for this one but there is that input hybrid in that the ceramic hybrid resistor there across jumping over from there but apart from that they do actually have the wires coming out from there and this one's actually been pinched so I'm not sure what what happened there but that one certainly has a bit of a rough life there once you get those four screws off for the input jacks there it does look like it just pops out okay it's probably a connector for the LCD or something and yep that's exactly what I thought it was just a point one inch our header there just required a bit of force to pull that out and I found something rather interesting already and that is Fluke 27 there it is rev five of the board the interesting thing is this was actually redesigned in 2003 there it is copyright 2003 fluke PC a digital rev well they've got a manual rev 8 on there and it looks like a fairly modern display processor down there I'm going to wow that's been proud like micro controller so I'm going to whip that label off and have a look what we have down in there that's seen version 2 there and I think we might find this is ATI msp430 like they use in the new model flukes let me get that off and we'll see and bingo I was right msp430 f4 37 there you go so they decided to redo this sucker maybe they couldn't get the ASIC chip or something that they used in the original model so they clearly redesigned this display board down here it would be interesting to compare with an original flute 27 and I used to have an original flute 27 a long time ago but unfortunately I don't actually remember and don't have any photos inside but they've clearly redesigned this in 2003 you can see the classic design fluke mechanism there with its forearms going like that that thing is never going to wear out and they've used a Kyocera brand PCB mount a buzzer they're spared no expense this looks like a programming header for the msp430 and there's nothing on the bottom so I won't bother taking that board out but I'd like it to tell me with that six shake proof washer screws there and you can see the zebra strips on the bottom there to connect through to the LCD so that's all sandwiched in place I rather liked that design and yes they haven't skimped on the shield in here have they folks I mean look at that it's almost completely enclosed except for the penetration for several things that's the buzzer on the bottom that meets up with the buzzer in there so it just pokes through and for the range suite they're just holes straight through the mounting holes of course there you go but apart from that it's Wow you know it's pretty well shielded and that looks like classic old-school fluke in there let's check it out and these are metal threaded inserts as I said that have captive nuts on the shielding on the other side absolutely beautiful I love it but there we go tada we're off Wow here we go folks this is old-school fluke here check it out they've even got the cutout for the main fluke ASIC down on there a classic wafer type switch here what an absolute classic package folks look at that it's the fluke 701 1/2 that's their internal part number this is their custom ASIC which contains a whole bunch of stuff which we can actually have a look at because it is inside the manual but it's the classic flat package they haven't formed the leads all and they haven't got all the leads coming out the unused leads I just trimmed off and this one's actually it's not what old stock or anything it looks like it was manufactured 13th week Oh for if that I assuming that is a date code it certainly looks like a classic date code there so they were still manufacturing this ASIC in this classic non lead formed package I love it so that aspect of the design I don't think has changed since this thing was first released there you go we have a recent fairly recent anyway in the scheme of things 1997 and date code and there's some high voltage isolation slots in there they've really gone to town you can see the little look at the little guard trace wiggle around there on that device I'm not sure what that is it could be a voltage reference to but they've added that little guard trace in there they thought they had to do that bit of attention to detail some classic style cylindrical tubular style or whatever the name is for those trimmer caps as some more trimmer caps down here there's a variable a couple of variable resistors there and that is the hybrid there's the ceramic hybrid there which would be the resistor voltage divider and these are actually very high voltage with standing Teflon dielectric capacitors hence because they're high voltage this still in the high voltage input part of the circuitry hence the high voltage isolation slot underneath it there these particular ones are rated to 1700 volts and I just love the old-style radial formed lead resistors there they used to use these in the older flick 70 series way back if you've got an original one of those crack it open and you'll see exactly the same thing I love it they really haven't changed much when they updated this thing and that maximum IC l76 one one that's a ultra low power dual op amp and the wafer switch system here is an absolute thing of beauty it's got jewel wipe contacts as you can see in there top and bottom ah man you don't see these much anymore that's just wonderful you couldn't buy that thing if you tried and if you want to see that fuse riser board up close there it is you can see some isolation slots in there there's some sort of plastic retention clip in the center which is kind of weird and check out we have a little ferrite on that input lead and what that thing is going to do is just take the edge off any serger any input surges and when the fuse blows and that device down in there is an IFC 23 eight one seven can't find any data on that if we looked at the schematic I buy the two pin nature of it there and they turn on its you package my guess and the guard trace around it my guess would be that is a voltage reference and here's our milliamp input see current shunt four point nine nine five ohms point two five percent there it's a biggie it's a couple of watts and right next to it there you can see the classic bridge rectifier and Daioh protection will ensure that the fuse is going to burst and not that big current shunt resistor on the milliamp range in gross overload conditions and of course the other limitation of this meter I forgot to mention and one thing you won't find on here is a true rms converter chip this is not a true RMS voltage meter it's only average responding and we've got no less than five mobs here for input fast surge overload protection but they've got four of them in series here to get the increased voltage and then it would dissipate the energy across the four devices instead of having one big monster one and the black device there is a PTC thermistor for the slower overload conditions and they've gone to the effort to go well we need some internal shield in as well so bugger it let's put on a big internal right angle shield and they haven't skimp there on the battery wires look at that they've put little crimp connectors on the end first and then soldered the whole lot in I love it now if you have a look at the teardown of the more modern 28 Series - I did you'll see the huge difference in just the construction of the input circuitry and the fuses none of this Raisa board stuff I mean this is actually fairly clumsy I mean it's ultimately well engineered in terms of you know how they've you know actually assembly of it but it's just you know it's just a clumsy design I don't necessarily like it from that point of view the the more modern flue 28 fluke have certainly learned a lot since they designed this I mean but this would have been the same design way back when this flue 27 first came out and you can see a 10-5 written in there and I do think that my particular unit here is 2005 vintage so it's only 7 years old not that bad at all now if we have a look at the schematic here for this main chip they call it an AP 25 this is the classic fluke proprietary chip set here which has a whole bunch of stuff in it of course it's got the ADC building it's got active filter buffer integrator input network selection input so it does the auto-ranging and all sorts of stuff and you can see the things surrounding it here let's have a quick look this at IC l76 double one ultra low power op amp up there with aj FET look at that love it part of the range switch here and you can see why this thing's going to get a thousand hours battery life because look it's driven by a thirty two point seven six eight kilohertz watch crystal I don't know if they multiply that inside but it's certainly not going to be running very fast at all I love it and there's our voltage reference down there one point two three volts and then there's a adjustment trim pot there to set that which goes in as the voltage reference we've got some more filter and some ADC sampling stuff around here and active filter components buffer integrator components and that and here's the digital output which goes off to the digital board as you can see there's a small data and address bus there it's only a 4-bit address bus and it's got various other stuff too end of conversions and clocks and all sorts of things which go off to the msp430 processor board which gets the data out of this thing and displays it and it even gives you a little description here of what's inside this custom analog IC and as you can see here it says that u1 also contains digital circuitry for the state machine control over the ad decoding ROM so it's it's got internal decoding roms and state machines in there which allows it to do all the auto ranging and the analog to digital converter and it tells you the ad conversion is accomplished using a modified dual slope the conversion method can be described as a charge coupled multiple slope technique a series of ten minor conversions occur every 40 milliseconds each at one-tenth the desired resolution without taking time for an auto zero phase between conversion there's these minor conversions or samples as they are called in the following discussion occur at a rate of 25 per second hence that's why they can get the fast response on the Biograph display at lower resolution compared to the screen so new samples are taken every 40 milliseconds tensing samples are some to produce the full resolution digital display and for the 3200 counts there you go so that is the basic operation here we go if we zoom out here that there is the basic operation of the ADC and the state machine I love it and that's all inside that custom Fluke ASIC which they've had for many many decades and no doubt they have a patent on and if we have a look at some of the specs here you can just see how awesome these are for a 3,200 count multimeter I mean not 0.1% +1 count on DC volts it drops to 0.2% plus one counts on the ohms range it gets higher outside of that of course it's still like Noor point two percent on the conductance range there plus ten counts of course diode only goes to two volts and the ACS you know not the best of course but that's alright and the current where's the DC current it's not that spectacular at 0.75% plus two but they're basically the ohms and volts are excellent specs for a three or four basic a three and a half digit multimeter and if you have a look at the specs here of course it's designed to survive almost anything it's a waterproof to one meter down here it's a shock and vibration and water resistant oil waterproof the whole thing thousand hour battery life it's absolutely massive and it's designed to operate I can temporarily operate down to minus 40 degrees C for 20 minutes I love it so there you have it that is the new model I guess you could call it our original fluke 27 the yellow and charcoal one as opposed to the original design which you would have seen which you would see if you take it apart would not have of course the new TI msp430 processor in there to drive the display so this is an interesting mix this meter of you know modern sort of you know a ret they've retrofitted an old design they kept a lot of stuff the same I mean the classic ASIC on the bottom there they were still able to manufacture that so they're still using it way up to 2005 and and presumably will be on that right up until they discontinued this model and it's basically the classic design which you'd pretend the wafer range switch here is probably exactly the same design they used in the original one and you know the vertical radial resistors they're absolutely classic design interesting blend of old and new so if you want to pick up one of is a fluke 27s which I highly recommend you do if you can get one cheaply do try and get the yellow and charcoal one the more modern one because it's going to last you a lot longer purely because it's not well you know 20 years old or something like that but by all means and pick up the older model as well because there as long as it's still in good Nick and the screen is still working well and hasn't faded or anything like that do pick one up because these are an incredibly robust and very accurate and very reliable basic 3200 count three and a half digit multimeter but just do be careful what you pay for one of these things I pay 40 bucks for this in practically brand-new condition so you know I I think I got a pretty good fire but there's still some people selling these for a couple of hundred bucks you know so they're they do tend to hold their value quite well but you I have bought a few of these in the past at very rock-bottom prices so if you just keep your ears to the ground you might be able to pick up one of these puppies I highly recommend it if you don't mind the size and the weight of course and the lack of some fashion functionality get on more modern meters it really is a good reliable meter to have I'll recommend it so if you want to discuss it jump on over to the AV blog forum and as always if you like these sort of tear downs and multimeter stuff please give it a big thumbs up catch you next time

Channel: EEVblog

Views: 58,103

Keywords: fluke 27, multimeter, review, teardown, 8025a, 8025b, fluke 25, fluke 87v, fluke multimeter

Id: MKuvmoW0AZQ

Length: 32min 38sec (1958 seconds)

Published: Wed Oct 17 2012