EEVblog 1448 - Convert a Fluke 77 IV to True RMS for 10 CENTS!*
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- čas přidán 24. 07. 2024
- How to convert a Fluke 77 IV average responding multimeter into a True RMS model 177 for 10 cents.
*Plus calibration gear
Should also work for converting a Fluke 83V to 87V
True RMS measurement vs Average Responding
And how to calibrate a Fluke multimeter.
Fluke 87V service manual with schematic: xdevs.com/doc/Fluke/87V/Fluke...
00:00 - Hacking a Fluke 77 IV Multimeter
00:35 - Is the Fluke 70 series discontinued?
01:15 - Fluke History
03:10 - I noticed something...
04:49 - The AD737 True RMS converter chip
06:04 - Theory of Operation
07:21 - What is Crest factor
08:58 - How do they do it?
09:25 - Fluke 87V Schematic and the custom ASIC
10:53 - Let's modify it!
12:58 - A sine wave is NOT a crest factor of 1
14:01 - Soldering
15:15 - Will it work?
16:46 - Calibration procedure
20:09 - Winner Winner Chicken Dinner
Why are Fluke meters so expensive? • eevBLAB 91 - Why Are F...
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#ElectronicsCreators #Fluke #Hack - Věda a technologie
FYI, Fluke responded, the 70 series not not being discontinued, it's just not on the Australian website. It is on the US website main page though.
Dave, that was the first thing I went to check after I hit play on the video!
good enough for Australia
Ask them to modify the cal routine so that you can skip directly to the ac calibration after mounting the... no wait. Lol.
Did they respond to this video? :)
I've had a 77AN for about 30 years. I was hoping this was something I could do with mine. I'm due to change the battery, I'll have a look inside.
so: 10 cents for the cap, and 10,000 dollars for the calibration equipment? ;)
I'm offering a service...
Just send your fully functioning 77-IV along with $US 500.00 and prepaid return packaging.
I'll convert it into a Fluke 177 INCLUDING a correctly labelled new case and even a manufacturers warranty!!!
I can also offer a similar service to convert other meters (at different prices of course)
For example, if you send me a fully functioning HP/Agilent/Keysight 3458A, I can convert that one into a Fluke 177 for only $US 300.00
Quite a bargain huh?
Or you can just pay few 100,000's of loan for a shop in a business building with a magic dumpster so that you can find those equipment "for free" ;-)
I dont think that calibrating a meter is such an expensive endeavor 😸
Nothing stopping somebody considering doing this from sending it out for calibration, for handheld meters, its generally pretty cheap from what I have heard
Yeah total clickbait.
I expect so much better from dave.
"Convert your fluke meter with only 10 cents worth of parts!*"
*cal lab not included, batteries sold separately, adult supervision required
Gee's its really obvious in this video how much work you have to put into a single video. Thanks.
And there is no "This video is sponsored by Skillshare" bullshit.
I just checked and my second Fluke is indeed a 77 IV from my time in the US Army. She’s going on 20 years old and still works like a champ.
My wife bought me an original Fluke 77 as a wedding gift in 1985. Still my favourite rugged, reliable DVM. Last year she found me {through her volunteer position with a local thrift shop here in western Canada} an older Simpson 470 DVM which is NOT auto-ranging, an advantage when I want to quickly check zinc-carbon, alkaline, NiCd & NiMH cells using the 2 volt range. I'll grant that modern metrology tools are generally superior, but instruments from many decades in the past still have their uses. I have a 1941-vintage 0 - 15 VDC meter made by Weston. Nicely finished wooden case, long mIrrored scale, still very accurate, but a little overdamped {slow to reach its final reading}. Calibration certificate inside the lid signed in india ink. 6 years older than I am !
great wife ;)
Checking the cells is pet peeve of cheap auto-ranging multimeres that have volts AC and DC on one dial position and they somewhat have AC as default.
@@Alexander-qz6px Just what I was thinking. Surely a keeper ;)
Analog mechanical meters are naturally true RMS and they aren't as affected by static and noise.
@@fieldlab4 a bit like being slow, you don’t get the joke’s being made about you.
I have not much clue about electronics , barely know what a diode is and a capacitor, but I like these videos cause I could follow your shematics and ideas at least and learned a lot.
I also had watched that previous video or from the other channel about the story why they are so expensive.
Thanks a lot.
Good on you - I, like many others, are in the same boat as you. I just really enjoy Dave's vids, and sometimes it goes way over my head, but I do enjoy the teardowns and listening to his reaction about the internals. He has a wide and varied library of vids - something for everyone!
Reminds me of the old school Radio Shack days. They would have something like 3 different radio models, low cost, middle cost and high cost. The higher cost ones supporting a larger range of bands. All you had to do was buy the cheaper one, cut a few resistors and bam, you have the most expensive radio.
You sir, are a damn GENIUS!! The world loves you for ALL the right reasons!
Cracking video, I love this sort of stuff I could watch it all day ! ...cheers.
I work for a transformer manufacturer company and when measuring excitation and no load loss of the transformer with no load connected the ieee standard calls for use of both an rms and avg reading meter. We use fluke 87 and 83 respectively for this. Has to do with confirming a sinusoidal waveform is being applied. If the values of each meter are off we have to apply a correction factor. And we annually get our meters calibrated by a third party cal lab to instill confidence in the measurements.
If only some handheld tool existed that could show a waveform ...
@@xorbe2 it’s the ieee standard. It literally calls out this method of testing. Must not deviate from it.
Looks like a simple and easy hack, but you also did a very good research on the topic. Very cool! 😎
Dave geeking out, as usual!
Yes, it is a very, very good idea to sell exactly same PCB (and 99% CCA) as multiple products.
Good product placement for the EDU33212A - great to see a successful upgrade too.
I thought I replied but it doesn't look like it went thought here's my comment again: To clarify/correct something around the 2-3min time mark: The 17x model is 20 years old but it has been updated internally since 2001. I have a preproduction revision from the 2004ish refresh that I can share photos of on the forum if there's interest. IDK if there's been updates sense but I'd be interested to compare mine with the current PCB.
My 77 IV is from 2003 so will it be the refreshed version?
Hi Dave, thanks BTW for stopping the trend you almost started 3 months ago. Your content speaks for itself!
Fluke 76, with the old 70 series design, and the 26III (same as the 79III) were also Trms.
Great video, by the way. Fantastic finding!
Amazing vid. I have a 21 year old 87iv that works just as good as the day it was made. Amazing.
Fantastic video, I have to say. Even though it of course needs to be calibrated to eliminate the error, it was for sure an interesting video.
That comparaison video sold me a fluke, love the quality
Good audio power amp with a step down transformer to get the 6 amps AC. Tearing down an old UPS backup can sometimes do the trick. I've also used the same to get up to 1000 volts AC with well a step up transformer. Using the audio amp with the function gen.
I had the same thought a few weeks ago and picked up a Crown DC-300 amp. Now I can hook my function generator up to it and have a peak of about 600W (120V at 5A) to work with. But first I need to rebuild the 30 year old amp. :)
BTW, Crown would demo them running a circular saw.
You legend!! Now I´m waiting for the tutorial on the conversion of the model 87 into 287 for only one penny (*plus calibration gear).
How about a well loved fluke 78? Seriously the most reliable meter I've ever had. I really don't need RMS for the most part, but I love this old meter. If I could add it well that would be cool. Thanks for all your hard work. It's always fun to watch.
On brymen DMM you can have nice thing of calibrating just the mode selection dial of your choice without the need to calibrate whole function or even whole full range of that particular measurement selection.
That actually makes sense since it's for the general market. If you think about it, the way Fluke has it set up also does, and is a necessity since they are used in production environments where its acting as a standard of one sort or another to verification of some part of the process. Seems tedious but after having worked for a number of years in a production facility I can say the temptation to just "fudge" it is always there for the techs, and engineers like myself while we are at it. Not out of malice or ill intent, but usually out of simple ignorance. Also makes it much less likely that the calibration can be corrupted, or a meter fault go unnoticed since the meter must pass all the steps before committing it to the EEPROM.
It would appear that if Fluke had added a tiny bit more circuitry, they could have maybe a small mosfet switch the filter cap in and out of the circuit on demand. Then a button on the front panel could select AVG/RMS. during calibration, pressing the yellow button could tell it to take two readings, one with the cap in and one with it out. I think building two models with such a minor difference was a missed opportunity considering it could have just had both modes in one.
If this doesn't make you simultaneously smile and shake your head, I don't know what will.
The 70 series is still offered on the site from the Netherlands but "Out-of-stock".
Also at 4:22 look at the top PCB writting... it's a "FLUKE 17X-30111 REV 015" board! Mystery has been solved! 😉 (Edit: DOH! Says it one second after I stopped the video. 🤦♂️😅 )
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The NL site doesn't list prices. Weird...
@@ZomB1986 It does on my end as it states: "€591,69
Prijs is inclusief btw" (Price is including Value Added Tax)
Djokovic ban means I have to buy fluke instead of an Australian product... good timing to see this 👌
Dave took a bullet for the team with the calibration! 👍😂
Hey Dave, can you look at reverse engineering the ROM cal values ? Maybe taking a dump of the average responding calibration vs the true rms ? This way we could tweak the values for the AC volts and leave the rest intact.
Next EEVblog product.... Fluke calibrator box. :D Thanks for the great video. Haven't we all done the same in some way shape or form? HEY, I can mod this to do that!!! Then you figure out that you didn't consider some step/part that makes it more expensive than just buying the other part. DOH! But, hey, it's still learning.
Awesome upgrade and cal video! Hilariously though, 177 sells for $311 on Amazon US vs 77 for $323.
Just another way to "force" model mobility.
😉
Amazon is just place where same item can have multiple sellers. It sux.
So educative... thank you very much!
This kind of approach goes way back. In the late 50's and early 60's the IBM 407 accounting machine was available (for rent only) for one price, and a double-speed version rented for a higher price. In order to make this change, a jumper was removed. I guess there was some mechanical wear argument for the increased price. I'm sure this is not the only example.
Same goes for outboard boat motors. The same basic motor may be sold with two or three different power outputs, sometimes with "actual" differences such as smaller carbs on the lower power model, sometimes nothing but a piece of plastic preventing the throttle control to reach full throttle.
Same was true for at least one mainframe computer that I'm aware of. Jumper added a wait state or two. CE's were threatened with termination if they removed said jumper without corporate approval.
Same with Keysight and their oscilloscope software "upgrades".
Fluke 76 was True RMS back in the 90-s when I've bought it. Works untill today just as new.
Most excellent Dave!
Once I buy my standards lab like you have I will have spent enough to buy 10 Flukes! Great Video! LOL
The keithley 175-av has the same thing, I believe it was a meter made for the government and/or the military and only needs a new cap and replace a resistor in a voltage divider to change the scaling factor in order to change it from average to trms it even has a similar chip (AD637).
great hacking video Dave!
I'm suprised they couldn't make that an option that could be turned on and off...
I guess they'd need to have two calibrations, -or- from your description: store the square root value of the capacitor chosen and use that value to determine true RMS vs Average.
Nice find!
"… a, you know, SCR switching waveform, which is like a switching, um, uh, thing" - Dave Jones, 2022 (8:10)
Отличный лайфхак! Спасибо за информацию, было очень интересно! Успехов в исследованиях!
Awesome work.
Great great Dave...
Just looked up the price ... I stick my with my aneng thank you very much
Great video.Thanks
On fluke 87v schematic you can find that model number is just 1 or 2 resistor away between 83v.
Dunno about F77-IV.
It's even easier to convert a Fluke 114 to enable diode & capacitance modes.
Just remove the internal dial stop tab, so the dial can rotate clockwise round to the next position after continuity.
88Hz, nice Back to the Future reference there 😂
The 77 IV is still available online with fluke in USA.
Wonderful info =D
"Spiffalorious". Thanks for the look.
Awesome stuff.
we have a lot of problems with Fluke 233, which consumes the five AA cells like candies - even then turned off. Often it continues in leaking cell, even from professional brands
well, that's 10cents + several tens of thousand of dollars of calibration équipement ! Of course you can just find these equipment for free in a magic dumpster but then it cost you several years of loan in a building with a magic dumpster. All in all it's still cheaper to buy the 177 directly.
The Fluke 87 is the model we see most used by professionals here in the 'States and it is true RMS.
Wonder if it's the same with Brymen 25x series and Greenlee 210/510.
Isn't there a way to hack into the eeprom containing the calibration values and only divide the AC values by 1.11 ?
Happy that it all worked, but how long did it take to finally calibrate the whole meater?
Makes me wonder what custom firmware you can get. Be able to get the temp sensor and also make the calibration more painless.
I guess: you can get any firmware you are willing to write (or have someone write for you) :)
@@absurdengineering that’s only if the system isn’t locked down. Hardware hackers can cycle power to skip instructions and such to break through some chip security systems, but if the OTP fuses are burnt there’s basically nothing you can do. For something that has official firmware updates it’s almost certainly possible, and for something that has its own calibration system like this DMM it’s probably possible, but who knows.
I always wondered if you can enable the temperature reading ability to the Fluke 177 like what the Fluke 179 has. Practically identical specs, even the 177 displays the C/F symbols when you do the display test on the meter. Anyone know or heard of it being done before?
You'd have to add the parts as per the schematic, and also chaneg the firmware.
Hi Dave. I'm a big fan. I got a well loved 88 mk1. Just wanna know if it also supports the AS737 true RMS chip?? Re, and keep up the good reviews!!!!!!
one question to EEVblog - do you search interesting equipment for tear down ? then you should check 1990s high end photo slide projectors. I tried to fix one and was completely amazed by it's processor control, dozens of sensors, switches, motors, solenoid actuators , triacs, and and and. i think i counted alone 6 different internal voltages.
This video really shows something I've been telling the production staff I work with ... People don't pay for the hardware or even the software in high end test gear ... Ultimately they care and pay for the calibration certificate
I'm searching for Dave's 77->177 upgrade kit - a 33μF cap and all the cal gear for 10¢ 😁
Don't forget the time you spend doing this.
You can install the cap and send it out to be calibrated at a cal lab. You’ll get a current cal that way, if that’s of much use. Still cheaper than a buying a new meter.
You can install the cap and send it out to be calibrated at a cal lab. You’ll get a current cal that way, if that’s of much use. Still cheaper than a buying a new meter. I wonder whether Fluke selects/screens those capacitors for higher repeatability between AC readings across different meters.
@@absurdengineering the meters cost roughly the same. Why bother?
I was on board with converting my old 77 Mk3 into a true rms until the calibration came up.
Makes you respect Fluke even more. For an encore I'll wager someone figures out Fluke does the mod for $50.
I've got a 1st generation 83 from the 1980's, non RMS (only the 87 was true RMS). I wonder what A/D chip is in there but I doubt it can be converted. Not that I really need it.
I am very happy with my BM786
I am retired now and don't need a Fluke. Very much appreciate Dave's investigation.
Calibration often a pain on the A*e, I had to buy a high current Rheotstat to calibrate current on a TTi power supply.
Getting 6A/60Hz is probably easy in US, if you happen to have a big mechanical variable resistor. Still I will refrain myself from using the power grid for "calibration".
The frequency does vary depending on grid load, though. So you would have to check the frequency and wait for it to be exactly 60 Hz.
Fluke 76 (mine) was also True RMS. It's a pretty old model.
I wonder how the HP 3400 RMS meter would read on the pulse?
IF you can afford all the calibration gear, you can afford a 177. Great video, fun discovery, but not practical.
actually the 177 is cheaper than the 77 nowadays, so maybe if someone pays you to keep his calibration gear during his honeymoon out of town ... otherwise ...
you can allways use a second meter in series / parallel to adjust your powersupply, no high end calibrator needed.
Yes more mods and upgrades please.
Haha love the 177 sticker 😆
I wonder if this can be done to the Chinese 17b+? That would be the perfect DIY Fluke meter except they crippled it by not including True RMS. No doubt this was done so it would not cut into sales of the 87-V.
Were off to "OHM'S SKI!" Ha ha
What a lab. "What a pain, I'll have to use all theses standards"
have fluke sent any men in black too you to have a whisper in you ear yet after letting this cat out of the bag?reminds me of the old mallard oc70x ceries of germ transistors,you had the oc71 then the oc71p photo transistor,the only difference was the price( the p was about 3x more expensive),used to just scrape the paint off the oc71 then voila you had the p version,later they got used to this and started filling them with a pale blue coloured gloope,used to twist the legs together then and stick them thru the holes inside of my mums hotpoint twintub spindrier drum and centrifuge the gloop from the junction,didny always work mut maybe 3 out of 10.
Hi! Thing of beauty is joy forever. Here's the model for those playing along at home. We're in like Flynn. "One hung low" brand flapping in a breeze. That's a bit "how ya doin". Power it up. Hello, hello? That's one sick puppy. It's upside-down, so all the electrons gonna fall out. Doh. Stupid me. Winner-winner, chicken dinner. Bob's your uncle. Give it a big "thumbs up".
It's a little weird to me that the 79 Series III is the one RMS meter in the 70 line, when the 79 Series II was also an averaging meter. (I have a Series II; it was a very fortunate thrift store find, back in the days when they didn't all peg their prices to ebay.)
I don't believe any of the original 70 series were true RMS.
This mod is well worth it IMO its probably not expensive to get it recalibrated somewhere anyway
Video on how you cobbled the current source ! Seriously, had to deal with this kind of junk before and gettign this kind of stuff is remarkably hard, especially once voltage/frequency/currents are beyond what an audio amp does comfortably.....
It was just my variable frequency/voltage mains supply into a 4 ohm load. Adjust voltage until it was near enough. It was only rated 4A though, so lucky it went to 6A. Certainly was not a good stable reference, I wouldn't recommend it!
@@EEVblog Ahh, that clears it up, thanks dave! So special equipment was involved. Last one for me was 20 kHz Sine at significant voltage, power converter + LCL could not be used because too much switching RF noise would always radiate and ruin the measurement. No incentive for a proper analog design because single use. Ended up using a semi class b/c with the same filter and a ferrite transformer to step up voltage. That was "fun".
So they could in principle add a switch or mode for measuring average or rms.
Probably not a useful thing, and wouldn't fix the problem with existing documentation of you wanted to replace an average measuring meter with a dual function. (You still need to add "be sure to measure in average mode" everywhere)
Edit: ah, and the calibration. Well, there's the switch idea out the window. ;)
Could there be a way to upgrade the 177 into 179?
I checked both PCBs and components of 177 & 179 are all identical and equal in numbers. There are no solder pads for jumpers to convert from 177 to 179.
I swapped LCDs, keypads and selector switches but no success.
Good thing with 179 is that it has added type-k thermometer function. If PCBs and component counts are the same, surely the 177 is thermometer-ready, it's just a matter of changing it's mode into 179 so one can utilize the temperature function.
Isn't the deal with these that US Navy has tons of manuals with procedures based on the old averaging method so they just keep producing them mainly to sell to the Navy?
Yep, they made the 27-II for that market too.
Thr other difference vs 177 model is that the 77iv has only autohold, so it lacks manual hold! How is this implemented in the circuitry?
can you make an inrush conversion on a clamp meter or an in-line device for a clamp probe?
There is one exception. The Fluke 76 is a true RMS meter. (I forget when they stopped selling it, probably soon after the 80 series came out)
That was a rare one. The 79 was the more common one in the series III that was True RMS.
I've got a few holes in that area, but I've got a good sampling of -III and I finally got a 77 IV.
@@EEVblog I took the cover off one of my 76 meters and wasn't surprised to see the 737 IC. What DID surprise me was the copyright date: 1994. Oddly, the 79 I took apart to see if it had the IC (it doesn't) was dated 1990, but it has the painted front. The 76 still has the decal. Sadly, I don't have enough later 79/29 examples to see if any of them have the IC without the capacitor.
What about 1st gen 77 from late 70's/ early 80's?
@@fieldlab4 I'm not sure what you are asking about them. Although the 76 isn't labeled as a series 2 meter, It was made around the same time as the other square 70 "series 2" meters. I was surprised it was made so long after the introduction of the 80 series meters. The last square 70 series meters were the 73-III and the 70-III. The remaning -3 meters were the tapered case with the overmolding. As Dave said, the 79-III was the TRMS, the 77-III was not. (Buit the older 79s were not, either. It's confusing)
Thanks for the interesting video. On the subject of T&M manuals I'm wondering if you might be able to help me? I am after a manual with circuit diagram and component ID's for a LUTRON DM6055C digital clampmeter (circa ~late 1980's). Yes, I know what you're going to say and No, LUTRON (Taiwan) don't do communications with customers for some inexplicable reason. Not even the distributor here has gotten anywhere with them. So I'm wondering, could what I'm after be found in some obscure hiding place? Any help appreciated. Thanks.
I have a Fluke 16 that started reading off for both AC and DC voltage. It reads high (12.6 v DC reads as about 15.4 and 124 v AC reads around 140v) is the meter shot? Or could it be recalibrated successfully?
How long before some manufacturer makes a multimeter with switchable true RMS?
Having seen the reasons in that previous video on why fluke are so expensive I realise there is nothing that I want in a multimeter , be it function or feature , that I can't get from many other manufacturers for way less.
So ten cent on top of $370 for true rms doesn't remotely pass the bargain sniff test .
With fluke you're not buying features, you're buying accuracy and a great lifetime meter. Of course if it's not a situation where you can really take care of it that's a waste. If it's a meter that's going to get beat up and abused get something disposable.
Okay Pros, who is going to mod the firmware to store more cal values and make a fluke that can flip between peak/average/rms on the fly?
Bravo. Love beating The Man !
Dave, will you do a review on cheap multimeter like those rebranded by Amazon? I'm thinking of the 90md610, going for 40€ here in Italy (claims to be a true RMS 6000 points job, with 10A to uA in both DC and ac) . Or other ~50 €/$ price range ones. Love you!
Watch the Aneng An8008/9 review could be considerable
@@Huzaliproductions i know, but here's retailing for around 60€ and every time I've ordered from China I've had nightmarish problem with custom /import office blocking packages.
@@REVOLUTIONS51 The meters in the "taobao special" grade with similar price range and the same sampling count willl be carbon copies of each other using the same chip with sometimes slightly modified PCBs. Don't overthink it.
Quick search through local suppliers in northern Europe tells me that 177 is 120-150€ cheaper than 77
You are awesome
Hi
Why fluke 179 is green backlight?
How change that to white backlight?