First Bench Multimeter - Fluke 8840a vs HP 3478a - Page 1
Forum section: electronics / testgear

author: gryffinwings
author_rank: Contributor
timestamp: April 10, 2020, 02:00:53 am
content: Hi guys, new here, I'm looking at getting some insight and advice on these 2 bench multimeter, the Fluke 8840a, and the HP 3478. So far the main issues I've seen with these is that the Fluke 8840a can have issues with a dim display due to being a VFD. The HP 3478a, on the other hand, will need a battery replacement to maintain the SRAM.Thoughts on either Bench DMM, accuracy between the two, recommendations, etc, appreciate any additional insight on these 2 DMMs.

author: jxjbsd
author_rank: Regular Contributor
timestamp: April 10, 2020, 02:39:07 am
content: The beautiful VFD display is still the decisive factor in choosing 8840A.

author: gryffinwings
author_rank: Contributor
timestamp: April 10, 2020, 04:06:45 am
content: Quote from: jxjbsd on April 10, 2020, 02:39:07 amThat is something I am considering, I love the way the display looks.

author: pqass
author_rank: Super Contributor
timestamp: April 10, 2020, 06:03:54 am
content: I've been VERY happy with my HP3478A that I've acquired in February of this year.Within the first two weeks I've managed to build a Arduino-based GPIB interface, download the the calibration data, and replace the battery thanks to the help of this forum. But I still have 4 RIFA caps to replace.I really like the 30mA range that can read down to 100nV (although it's a bit jumpy); it can read thermocouples directly! I've only had hand-held meters so this was a step up for me.Regarding the spec differences, the 3478A is a 300K count meter vs. 100K for the Fluke. Check out the meter spreadsheet here:https://www.eevblog.com/forum/testgear/multimeter-spreadsheet/Although a bright VFD is nice, I cured the hard-to-read LCD problem with an IKEA JANSJO lamp.I think I did alright for US$100 price I paid for it.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 10, 2020, 07:14:22 am
content: The 3478 has high Z only up to a little over 3 V. The Fluke 8840 has high Z up to 20 V. With the Fluke meter AC is optional.I found the HP meter relatively easy to use, the LCD is sometimes a little difficult to read with poor light or from some angles, but still OK. AFAIK one still needs cold junction compensation, but the resolution is good, thanks to 30 mV range.

author: gryffinwings
author_rank: Contributor
timestamp: April 10, 2020, 08:37:45 am
content: Quote from: pqass on April 10, 2020, 06:03:54 amThe little projects that you've done for the 3478a is pretty awesome, also instead of GPIB did you mean HP-IB? That is definitely something I would be interested in. The battery part has me a little nervous, I've been watching youtube videos, not sure what route I would go exactly as I do not have all the extra equipment for isolation.

author: Mp3
author_rank: Frequent Contributor
timestamp: April 10, 2020, 09:51:17 am
content: I am also looking to get my first bench meter and the non backlit display is the only reason I haven't jumped on a 3478a. Though, i've managed with no backlight on my Fluke handheld meter all these years.I'm confused if it would be compatible with the leads from my Fluke 101 though.I do worry a bit about the EPROM and all the old IC's on the 3478a. The calibration being in SRAM is bad enough, but not the end of the world.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2020, 12:01:29 pm
content: I'd buy neither. Get a Vici VC8145 bench meter instead. It has more features and a way better display.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 10, 2020, 12:27:00 pm
content: Quote from: Mp3 on April 10, 2020, 09:51:17 amI would not worry so much about the EPROM - AFAIK there are images around, so one could get a replacement.The tricky parts are more the HP hybrid chips and special resistor networks. They don't fail very often, but are hard to get (more like a broken meter for spares).However essentially all higher grade DMMs use some custom chips or resistors. The fluke meter also has a custom chip and quite some critical resistors in the ADC.

author: pqass
author_rank: Super Contributor
timestamp: April 10, 2020, 02:45:13 pm
content: "...did you mean HP-IB?" Yes, I use HPIB/GPIB interchangeably.Before I did anything, I wanted to have a copy of the calibration data. This is what I did...Thanks to WaveyDipole (see:https://www.eevblog.com/forum/projects/ar488-arduino-based-gpib-adapter/), I connected my Arduino as per the simplest configuration in Appendix A (see:https://github.com/Twilight-Logic/AR488/raw/master/AR488-manual.pdf). Installed Version 0.48.08 of his software, verified connectivity with the meter and got familiar with the command-set.I then created the following program (a.c):Code:#include <stdio.h>#include <unistd.h>void main() {for(int i = 0; i < 256; i++) {printf("W\033%c\r++read\r", i);fflush(stdout);usleep(500000);}}Before executing the ./a program, I started recording to a gtkterm log file (newstcal1.log).$ gcc -o a a.c$ ./a >>/dev/ttyACM0$ awk <newestcal1.log '{printf "%s", substr($0,1,1);}' >newestcal1.calThe last line above copies the first character of each log line to a "cal" file.For better readability (broken into records and hexdumped) execute:$ cat newestcal1.cal|od -A x -t x1z -w13 --skip=1000001 40 40 40 42 48 47 43 4c 4d 40 42 4d 40 >@@@BHGCLM@BM@< 30 mV DC // 000000e 40 40 40 40 42 48 43 4c 4c 42 41 4d 47 >@@@@BHCLLBAMG< 300 mV DC // 100001b 40 40 40 40 40 43 42 45 43 41 45 4e 4c >@@@@@CBECAENL< 3 V DC // 2000028 49 49 49 49 49 44 43 4c 4c 4f 4d 49 47 >IIIIIDCLLOMIG< 30 V DC // 3000035 49 49 49 49 49 49 42 45 43 4e 4d 4a 44 >IIIIIIBECNMJD< 300 V DC // 4000042 40 40 40 40 40 40 40 40 40 40 40 4f 4f >@@@@@@@@@@@OO< <not used> // 500004f 49 49 49 40 43 48 42 43 42 43 43 4c 4c >III@CHBCBCCLL< AC V // 600005c 49 49 49 49 43 47 40 45 45 40 44 4c 43 >IIIICG@EE@DLC< 30 Ohm 2W/4W // 7000069 49 49 49 49 49 44 40 45 44 42 4e 4b 45 >IIIIID@EDBNKE< 300 Ohm 2W/4W // 8000076 49 49 49 49 49 49 40 45 41 41 4d 4b 45 >IIIIII@EAAMKE< 3 kOhm 2W/4W // 9000083 49 49 49 49 49 49 40 45 40 40 42 4c 42 >IIIIII@E@@BLB< 30 kOhm 2W/4W // 10000090 49 49 49 49 49 49 40 45 41 4e 4f 4a 46 >IIIIII@EANOJF< 300 kOhm 2W/4W // 1100009d 49 49 49 49 49 49 40 45 4f 41 42 4b 42 >IIIIII@EOABKB< 3 MOhm 2W/4W // 120000aa 49 49 49 49 49 49 40 45 42 44 40 4b 4e >IIIIII@EBD@KN< 30 MOhm 2W/4W // 130000b7 49 49 49 49 49 48 44 4d 4e 4d 4c 49 42 >IIIIIHDMNMLIB< 300 mA DC // 140000c4 40 40 40 40 40 40 44 4d 4c 43 40 4d 4f >@@@@@@DMLC@MO< 3A DC // 150000d1 40 40 40 40 40 40 40 40 40 40 40 4f 4f >@@@@@@@@@@@OO< <not used> // 160000de 49 49 49 40 43 48 43 44 42 42 4c 4c 42 >III@CHCDBBLLB< 300 mA/3A AC // 170000eb 40 40 40 40 40 40 40 40 40 40 40 4f 4f >@@@@@@@@@@@OO< <not used> // 180000f8 40 40 40 40 40 40 40 40 >@@@@@@@@<I then verified each of the records above using the following pseudo-code (checksum is in  positions of each entry):Code:for(byte cksum = 0, int j = 0; j < 19; j++, cksum = 0) {for(int i = 0; i < 11; i++)cksum += (entry & 0xf);cksum += entry << 4cksum += entry & 0x0fif (cksum == 0xff) then SUCCESS!!!!}1st entry example (ignore the leading nibble): (0+0+0+2+8+7+3+c+d+0+2)+d0+00 == ffOnce that was out of the way, I moved onto the hardware.After studying the schematic, I determined that the simplest and safest solution was, WITH THE 3478A POWER PLUG DISCONNECTED, to solder a "pig tail" with series 330R resistor and signal diode to the cathode of CR500 and ground-side of a nearby bypass cap. Before committing, I checked that I had the right trace by using my hand-held meter to confirm that it had +3V (lithium battery) when the 3478a was powered off and +5V (meter main digital power rail) when the 3478a was powered-on.I then turned on the 3478a to confirm the calibration was still okay. It was, and the hard part was over.WITH THE 3478A POWER PLUG DISCONNECTED, I then attached a battery holder with 3 AA batteries to the pigtail. Again, using my hand-held meter, I confirmed that the cathode of CR500 had +4.5V with the new battery holder attached and +3V (lithium battery) without it. I left the new AA holder attached, then proceeded to cut-out the old lithium battery (at the spot-welded points) leaving two lead stumps. Again, I then turned on the 3478a to confirm the calibration was still okay. It was.WITH THE 3478A POWER PLUG DISCONNECTED, I then soldered in the new lithium battery and disconnected the AA battery holder. I left in the pigtail for the next guy.No isolation  was required. Just planning and an extra battery.P.S.Much thanks to this thread:https://www.eevblog.com/forum/repair/hp-3478a-how-to-readwrite-cal-sram/

author: Mp3
author_rank: Frequent Contributor
timestamp: April 10, 2020, 04:31:57 pm
content: @pquass- Great work and writeup, tyvm! I don't really wanna mess with still working test equipment too much, but i was thinking about replacing a few of those filter caps with fresh ones while i was in there.Quote from: nctnico on April 10, 2020, 12:01:29 pmThis meter looks nice, but it's about $150 at its cheapest, and I am able to get a self-test verified 3478a for $40.I had considered all these options before, but the Fluke is just too old for me. The 3478a is at least as old as I am.Quote from: Kleinstein on April 10, 2020, 12:27:00 pmMakes sense. But custom resistors? I thouht all resistors were "off the shelf" so to speak....The EPROM I didn't realize is a standard 64kb, i thought at first it was one of the older ones in a 26 pin package.Hmm, i could program a spare 27c64 OTP with the image just as a preventative measure. Hard to say if it's worth waiting until the electrons get loose from the EPROM.

author: pqass
author_rank: Super Contributor
timestamp: April 10, 2020, 04:34:31 pm
content: Shrouded banana plugs WILL NOT fit in the 3478a.I appear to have a ROM, not EPROM in my '88 vintage 3478a.See previous post picture.

author: Mp3
author_rank: Frequent Contributor
timestamp: April 10, 2020, 04:49:48 pm
content: Quote from: pqass on April 10, 2020, 04:34:31 pmI noticed that, from checking them out on google image search, seems a variety of chips was used, i saw at least 3 different brands looking at google image results. I'll hope there is an OTP chip in mine. As long as they all use the same binary, its all good.

author: pqass
author_rank: Super Contributor
timestamp: April 10, 2020, 04:56:43 pm
content: "...thinking about replacing a few of those filter caps..."My filter caps seem fine so I wasn't thinking about touching them.Although, I vaguely remember reading in the forum it may improve the meter readings.But the 4 RIFA caps on either side of the transformer have got to go.They show hair-line cracks. Good thing I don't use the meter in the shower!

author: Kleinstein
author_rank: Super Contributor
timestamp: April 10, 2020, 05:29:40 pm
content: Quote from: Mp3 on April 10, 2020, 04:31:57 pmIn the 3478 the critical resistors are inside the 2 custom hybrids. So likely no extra custom resistors in this meter - but as part of the hybrids. So in theory these can also fail from resistor drift. However with the integrating ADC resistor drift would mainly cause gain changes that can be compensated to a large extend.For the old ROMs there is the option to use adapters to a EPROM can be used in the ROM socket.Replacing the filter caps is mainly for the possible smell and smoke in case they fail. Don't expect any change in noise. It would be only right before the magic smoke escapes that a bad cap may also add noise.

author: Back2Volts
author_rank: Unknown
timestamp: April 11, 2020, 03:55:29 am
content: Quote from: gryffinwings on April 10, 2020, 04:06:45 amI have one and the display is very nice. It is seating next to a 805A, and what a difference!

author: Mp3
author_rank: Frequent Contributor
timestamp: April 11, 2020, 04:21:02 am
content: Thanks for the clarification on the resistor networks. I 'm not terribly concerned about it, unless the meter begins to act wild.Yeah, i have no intention of replacing the caps expecting it to make any difference in the operation of the multimeter. I figured they're old, crusty, dried out and it wouldn't hurt to replace them before they give out, if I'm going to have this unit in frequent operation. (C761 - 3300uf 25v , C711 - 1000uf 25v , C703 & C702 - 330uf 50v)i didn't realize you can get access to the bottom of the main board without removing it from the chassis, so this should be very easy to do i think.BTW - I am planning on DIY'ing some test leads for my 3478a. Part of the reason I got it for such a low price was it was just the unit by itself. I was planning on using some spare unsheathe banana plugs I have on hand, since they're nice quality and I already have them. But they're the gold plated A/V type by Mediabridge. I didn't think there would be any problem using these - as long as they fit at all - but then I came across this post by one of the designers of the 3478, suggesting to use copper tubing for a DIY plug? Any thoughts on this...?https://groups.io/g/HP-Agilent-Keysight-equipment/topic/29423423?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,40,29423423I know unshrouded is dangerous for high voltage but I can't remember the last time I measured anything higher than 24VAC, and I have my handy-dandy Fluke 101 just in case i find myself needing to measure 600V.

author: gryffinwings
author_rank: Contributor
timestamp: April 14, 2020, 04:47:25 am
content: Quote from: pqass on April 10, 2020, 02:45:13 pmThank you so much for the write-up!I'm also not sure what your are referencing in this"to solder a "pig tail" with series 330R resistor and signal diode to the cathode of CR500 and ground-side of a nearby bypass cap. "Could you explain this part a little more clearly, what parts you are you referencing? and where they go, and also where you ended up solving the battery setup to.

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 14, 2020, 01:15:45 pm
content: Are the HP meters region specific in terms of socket voltage? I can't figure out if there's some switch to select a different voltage like there is on the fluke.

author: Venturi962
author_rank: Regular Contributor
timestamp: April 14, 2020, 02:58:23 pm
content: HP 3478A is line switchable, you'll have to open it up to do so.Video from VoltLog on the subject:

author: pqass
author_rank: Super Contributor
timestamp: April 14, 2020, 03:52:03 pm
content: Quote from: gryffinwings on April 14, 2020, 04:47:25 amI've been meaning to do a writeup for this forum but also to print and include in the meter itself for the next guy (which will likely be me).The "pig tail" is the white+red wire lead pair with a 100mil female connector on one end and a 330R resistor+diode on the red wire on the other end.See top view image below on how I've attached it; red wire (after my diode) to the CR500 diode (cathode side) and white wire to a nearby bypass cap (GND side).Before cutting-out the old soldered-in lithium cell, the female connector of the pigtail is attached to any battery that is greater than 3V but less than 5V. In my case, I used a 3 cell AA battery holder (which is nominally 4.5V). Being a different voltage (higher than the lithium battery) allowed me to confirm with a hand-held multimeter that pin 22 of the RAM was actually getting its voltage source from the pig-tail battery. After the lithium battery is replaced, you can remove the temporary battery holder (leaving the pigtail, as shown, in for the next time).Basically, I've replicated the same "wired-OR" circuit that the soldered-in lithium battery uses to gate its voltage onto pin 22 when the main 5V power rail is turned off. See BT701, R765, CR764 in Figure 7-G-6.DISCLAIMER: I've got a 2619Axxxx serial unit which seems to correspond to the 2nd set of schematics in the service manual located just before Appendix A. Your unit may be earlier. In which case, my CR500 is equivalent to CR520 as it appears in the 1st set of schematics in Figure 6-5. I don't know if CR520 is similarily placed in these earlier boards.https://www.qsl.net/n9zia/test/HP3478_Service_Manual.pdf

author: gryffinwings
author_rank: Contributor
timestamp: April 15, 2020, 12:16:38 am
content: Well, it looks like I'm getting an HP 3478a soon, it just seems to be a lot more of them available at the price I would like to pay. After that, all I need will be an Oscilloscope and a Power Supply.Thank you for all the information, I feel much more confident replacing the battery in an HP 3478a and not messing up the calibration data.

author: nctnico
author_rank: Super Contributor
timestamp: April 15, 2020, 12:28:34 am
content: Have you ever used a HP 3478A? The LCD display is just horrible to read. Get something with backlight, VFD or LED. Read my previous suggestion; that is what I ended up with after a similar search like yours. Old DMMs just don't have the bells & whistles modern DMMs have. Older DMMs typically seem to have low current handling abilities too. 3A is quite limited.

author: pqass
author_rank: Super Contributor
timestamp: April 15, 2020, 01:43:39 am
content: Quote from: nctnico on April 15, 2020, 12:28:34 amWell, sure you could always spend more to get more features.But I can buy three 3478s (~US$135) for every 34401 (~US$400) on eBay.They both have the same LM399 reference, are 300k count, and have a 30 or 100mV low DC range with 100nV resolution! Sure, the 34401 is a more accurate, overall better meter but for me, the 3478 is more than good enough to work on op amp and other analog circuits. It gave me 3 extra right-hand digits compared to my hand-held meters.The display readability can be solved with a clip-on LED goose-neck task light or even an HPIB-connected Arduino-based LED display (see AR488 project elsewhere on this forum) . Some guy elsewhere on the forum even reverse-engineered the LCD protocol and replaced it with an LED equivalent! It seems quite hack-able for a hobbyist.Of course, I don't do professional work so price matters to me.

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 15, 2020, 02:56:33 am
content: Quote from: Venturi962 on April 14, 2020, 02:58:23 pmThanks, great link.Does anyone also know whether this HP 3478A can measure voltage and current at the same time?

author: pqass
author_rank: Super Contributor
timestamp: April 15, 2020, 04:26:04 am
content: Quote from: gryffinwings on April 15, 2020, 12:16:38 amDepending on your power supply needs, you can search eBay for HP E3610A, E3611A, E3612A, or E3620A.They have detailed manuals and are quite fixable (lots of Youtube videos).Dave sings its praises here:

author: pqass
author_rank: Super Contributor
timestamp: April 15, 2020, 04:32:34 am
content: Quote from: PixieDust on April 15, 2020, 02:56:33 amSadly, no.

author: J-R
author_rank: Super Contributor
timestamp: April 15, 2020, 05:02:47 am
content: The 34401A is actually 1.2 million count. You can tease it into displaying 1,200,000 very briefly. But I guess technically you should say it's 1,999,999 count.I seriously considered the 3478A and the 3457A before deciding on the 34401A. The 34401A doesn't have a battery to keep track of and does have a serial port. I ultimately decided it didn't make sense for me personally to have any of them unless they were calibrated and I had the calibration data to refer to.So yes, the 34401A is a bit more money but I hunted for a few months before snagging one in great shape with a current calibration plus calibration data printout for ~$400US. It's basically spot on and the last calibration didn't require any adjustments, so I have high confidence in it. It is an HP branded unit with the black terminals.I just received my PDVS2mini and after letting things sit for a couple hours was a bit surprised to what I came back to, so I just had to stage a mini photo shoot.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 15, 2020, 05:14:30 am
content: Unless you shell big $$ for a true dual independent channel dmm like ADCMT DMM 7352E you'll have to do it with 2 meters ...Or maybe do some tricks with meters who have scan cards in them ?? like an hp34970 who's like an 34401a brother meter but doesn't go to 1kv measurements.

author: pqass
author_rank: Super Contributor
timestamp: April 15, 2020, 06:07:27 am
content: My bad. I read the wrong column in the multimeter spreadsheet.Again, there's no question the 34401 is a better meter especially a calibrated one for US$400.However, between the meter and the PDVS2mini, the tally for me would be CA$950 before delivery, customs brokerage, and sales taxes. If I was making money with it, that would be a different story.The battery doesn't bother me that much since I've got a way to download/upload the raw values (via HPIB), an easy way to replace the battery every 10 years, and see only a future cap replacement. I am more concerned about replacing a possibly hard-to-get faded VFD in the 34401 and SMT reworking.Yes, I don't know the state of my calibration. All I do know is that it's consistent with my other 4000 count meters (which is not saying much). I guess I could buy a couple/three of ADR4530s from different distributers and make my own reference standard (that would put me +/-600uV off). That is, until I find someone with a better meter to do an informal calibration. But at least I have 32 years on the LM399 so it's done most of its drifting by now, which is nice. :-)

author: J-R
author_rank: Super Contributor
timestamp: April 15, 2020, 06:55:49 am
content: Sure, I wasn't suggesting all that for everyone, it was just my personal decision. The principle thought was why have the resolution if the accuracy is an unknown?I think a good option is to get the DMMCheck Plus and then also the VREF-01 at 5V from Voltagestandard.com. If they start to disagree you can send them out for calibration...

author: J-R
author_rank: Super Contributor
timestamp: April 15, 2020, 07:02:41 am
content: BTW, I was actually able to get the 34401A to display a completely stable 1.200,002V reading in manual range mode. At 1.200,003V it goes into OVLD. So I say it is officially a 1,200,002 count meter at least in my tests.

author: nctnico
author_rank: Super Contributor
timestamp: April 15, 2020, 09:39:28 am
content: Quote from: pqass on April 15, 2020, 01:43:39 amThat is the kicker... you don't have to. I make money using my test equipment and still my daily driver DMMs are two VC8145 bench DMMs. Sure a lot of people attribute all kind of magic properties to old A-brand equipment but if you purely look at bang for your buck then things don't look to good for the older bench DMMs. I have a (bought new) Keysight 6.5 digit DMM too but I rarely use it.

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 15, 2020, 11:13:20 am
content: What happens if you take out the battery from the HP3478A? What I mean is, it doesn't break, you just need to send it off to get calibrated right?

author: pqass
author_rank: Super Contributor
timestamp: April 15, 2020, 12:15:07 pm
content: Quote from: PixieDust on April 15, 2020, 11:13:20 amCorrect.Or, if you had a DMMCheck, you can do it yourself (see bottom of page 5 of Feb '83 HP Journal):http://hparchive.com/Journals/HPJ-1983-02.pdf

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 15, 2020, 12:23:46 pm
content: Ah awesome, thanks for the link!

author: pqass
author_rank: Super Contributor
timestamp: April 15, 2020, 12:43:21 pm
content: Quote from: J-R on April 15, 2020, 06:55:49 amDon't get me wrong, I would love a 34401 but realistically the 3478 is too compelling for its price and is good enough for my needs. I am immensely greateful that these meters are still accessible to hobbyists. I'm pretty sure it won't be my only meter for too long.I only got the 3478 in February of this year. I've been reading up on the whole accuracy thing without being sucked into the voltnuttery world so I'm not trusting the small digits until I sort that out. Thanks for the vref recommendation. I don't require a cal certificate, I'm only needing the occasional comparison/adjustment with a better meter (like a 34401).

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 15, 2020, 01:47:52 pm
content: How are these units calibrated (HP 3478)? Over GPIB?

author: pqass
author_rank: Super Contributor
timestamp: April 15, 2020, 02:12:02 pm
content: Quote from: PixieDust on April 15, 2020, 01:47:52 pmThrough the front panel; no need to open.It's a particular push button sequence + turning the "Cal Enabled" screw on the front panel.The previous HP Journal link, page 6, explains it. You don't even have to use a precise 10.000V standard; you can just use the arrow keys to dial-in the specific vref value as written on its faceplate and the meter will figure out the correct cal constant.Alternatively, hats off to these guys which seem to have cal tweaking via HPIB done and dusted:https://www.eevblog.com/forum/repair/hp-3478a-how-to-readwrite-cal-sram/msg3011668/#msg3011668

author: gryffinwings
author_rank: Contributor
timestamp: April 15, 2020, 07:43:52 pm
content: Well, I've finally got my have an HP 3478a on order from a well-rated retailer that's been on eBay since 2005, so I believe that I can trust this particular seller, also they are in California, so shipping to me is going to be much faster to me, even says I will have my DMM this Friday.

author: gryffinwings
author_rank: Contributor
timestamp: April 15, 2020, 07:58:34 pm
content: Any recommendations on some test leads, since this one doesn't come with any?

author: J-R
author_rank: Super Contributor
timestamp: April 15, 2020, 09:43:32 pm
content: Looks like it needs non-shrouded...

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 16, 2020, 12:38:25 am
content: Quote from: gryffinwings on April 15, 2020, 07:58:34 pmApparently Pomona is the brand that supplies leads to Fluke. They have silicone casing which means they'll last decades.

author: pqass
author_rank: Super Contributor
timestamp: April 16, 2020, 01:28:22 am
content: Quote from: gryffinwings on April 15, 2020, 07:58:34 pmShrouded banana plugs won't fit.So if you can't find any without, you can always get a shrouded set for the meter and cut it off with a utility knife.

author: AVGresponding
author_rank: Super Contributor
timestamp: April 16, 2020, 05:30:58 am
content: Pomona make rectractable shroud leads, 6366 is the model I think?

author: J-R
author_rank: Super Contributor
timestamp: April 16, 2020, 08:11:37 pm
content: Well, if you don't mind cutting:https://www.ebay.com/itm/Agilent-HP-Keysight-5180-6661-Standard-Lead-Set-34132-37904-NEW/283738612273If you want the ones with the HP logo, be sure to talk to the seller first or you may get Agilent.

author: GreyWoolfe
author_rank: Unknown
timestamp: April 16, 2020, 08:20:23 pm
content: You can get Probemaster 8010S leads without shrouds and they are fairly cheap-$19.

author: wizard69
author_rank: Super Contributor
timestamp: April 16, 2020, 11:15:15 pm
content: Quote from: nctnico on April 15, 2020, 12:28:34 amVery good advice. Bad LCD screens are easy to deal with on handheld meters not so easy to deal with on bench meters. In the case of this thread I'd chose the fluke simply because of the screen.

author: gryffinwings
author_rank: Contributor
timestamp: April 17, 2020, 12:57:57 am
content: Quote from: AVGresponding on April 16, 2020, 05:30:58 amThese ended up being the best deal, so I have them on order.

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 19, 2020, 01:41:23 pm
content: Does anyone know whether there is some way of telling an older HP 3478A from a newer one? For example, one unit in the attachments, has a white serial number sticker, the other one has a dog tag style sticker. Any ideas what the numbers mean?

author: pqass
author_rank: Super Contributor
timestamp: April 19, 2020, 03:03:13 pm
content: Quote from: PixieDust on April 19, 2020, 01:41:23 pmSee section VI of the service manual here (https://www.qsl.net/n9zia/test/HP3478_Service_Manual.pdf).In 6-1, you will see a list of serial number prefixes and the changes that were made.If by "older" you mean when the case became a one-piece slide-off, it looks to be around serial 2545A26015 and below.See: "6-16. 2545A26015 & below. These instruments have a different cover and frame design."Also note on the 2nd page: "Serial Numbers: This manual applies directly to instruments with Serial Number 2619A37795 and above." I have not been able to find a later revision of the manual summarizing the changes afterwards.Additionally, I'm unsure when the front "hp" black/blue logo changed to all black bold lettering. It happened sometime after 2619A46100.

author: PixieDust
author_rank: Frequent Contributor
timestamp: April 20, 2020, 10:02:24 am
content: Thanks, so basically the bigger the numbers, the newer the unit. Sorry for asking stupid questions. Everyone keeps pointing to the service manual or the manual for answers.

author: PixieDust
author_rank: Frequent Contributor
timestamp: May 21, 2020, 12:42:38 pm
content: Finally found one HP 3478A on ebay that I liked. Not the deal of the century by any means but oh well. Looks to be in good nick. Will take a while to arrive. Just need to order the probes, new battery, appropriate fuse and rifa cap replacements.

author: PixieDust
author_rank: Frequent Contributor
timestamp: May 29, 2020, 02:38:51 am
content: Given that Australian mains is 230V @50hz but the unit (3478A) only has line voltage options of 220V vs 240V. I take it I should choose 240V?

author: guenthert
author_rank: Frequent Contributor
timestamp: May 29, 2020, 03:22:49 am
content: I saw the thread late and while I have multiple multi-meters, I don't have a 8840a (or any Fluke). I was about to comment on the VFD (I got a 34401a and 34410a, both with the blue VFD and a Datron 1271a with the beautiful emerald VFD), but since you already got your 3478a, I won't. Instead I keep it positive: the combination of (limited) resolution and good voltage reference in the 3478a assures very stable, satisfying readings (none of the silly ppm hunts the volt nuts engage in).

author: Kleinstein
author_rank: Super Contributor
timestamp: May 29, 2020, 08:13:41 am
content: The 240 V setting is likely the better choice: less heat produced by the linear regulator. The 220 V setting would be also OK (no damage), but more heat. It would be an option when the voltage sometimes drops down to low.

author: PixieDust
author_rank: Frequent Contributor
timestamp: May 29, 2020, 08:37:43 am
content: Thanks Kleinstein. Explains why it was set to 220V as it came from a country with 230V mains.guenthert - I did some research on the unit, I think it will do more than I need from it. I also came to conclusion from my research that it's a capable little beast as you pointed out. As for the display, I was aware about its display limitations. I thought about it and realised that the benefits of more easily readable displays of newer units didn't worry me. Newer units are much more expensive. I couldn't justify spending extra just for some nicer displays or perhaps higher digit count or other more modern features.I didn't ask or see if the unit past "Self Test" from the seller, assumed everything was fine since the seller didn't mention anything wrong with the unit. Turned it on now and thankfully no calibration is required. Looks like I'm a happy camper.Now the fun task of replacing the RIFA capacitors without doing something stupid and erasing the calibration data. I can only see 2 of these suckers in this unit.

author: PixieDust
author_rank: Frequent Contributor
timestamp: May 29, 2020, 10:43:19 am
content: How did you guys buy a replacement battery? Digikey doesn't ship batteries to Australia because they only offer air freight. I don't really want to ship to a freight forwarder because that's going to cost a couple of hundred bux. I'm looking to buy other stuff like probes for the multimeter and some more oscilloscope probes and a bunch of other electrical components but still, I'll probably have to spend around the same amount that the contents of the package cost if I use freight forwarders. I can't find anyone local selling those batteries or ones like it. I'm seeing folks from all parts of the world replacing with these digikey batteries. How did you catapult them over to your side of the pond?

author: MarkL
author_rank: Unknown
timestamp: May 29, 2020, 03:16:06 pm
content: Quote from: PixieDust on April 15, 2020, 02:56:33 amNot in a single acquisition, as others have already replied. But I wanted to add that it's possible to make the 3478A measure voltage and then measure current without manual intervention. (Another interpretation of "at the same time".)There needs to be a common node for the the current and voltage connections, and neither value should be changing rapidly since they're sampled at slightly different times. It can be done under computer control for minimum delay. I do it a lot for logging applications. The advantage is that it only needs one meter (and this is not unique to the 3478A).

author: PixieDust
author_rank: Frequent Contributor
timestamp: June 19, 2020, 08:39:36 am
content: Is there any difference between the different types of capacitor types:https://www.digikey.com.au/products/en?keywords=capacitorAluminum - Polymer Capacitors (10938 items)Aluminum Electrolytic Capacitors (124793 items)Capacitor Networks, Arrays (2870 items)Ceramic Capacitors (739512 items)Electric Double Layer Capacitors (EDLC), Supercapacitors (1718 items)Film Capacitors (69122 items)Mica and PTFE Capacitors (9027 items)Niobium Oxide Capacitors (476 items)Silicon Capacitors (266 items)Tantalum - Polymer Capacitors (13220 items)Tantalum Capacitors (103600 items)Thin Film Capacitors (4197 items)Or as long as the type e.g. Y2, lead spacing, voltage and capacitance ratings are the same you're good to go? I found the exact same capacitors that are in the meter, but I'm not sure if it's worth replacing RIFA with RIFA and just replace them again every 10 years or so or if I should just look for a more permanent solution.

author: Kleinstein
author_rank: Super Contributor
timestamp: June 19, 2020, 09:13:13 am
content: The capacitor types are quite different. In some cases one can choose different types, but not allays.The Y1,Y2, X1,X2 markings on capacitors are safety ratings: the Y class are safe against a short. The X class caps are supposed to no cause a fire when they fail. Both markings can be important. Such caps are often used in EMI suppression at the mains side. RIFA is just one large manufacturer for such EMI suppression caps with some old series showing aging and failures. Other manufacturers also has failing caps - so failing caps is not an RIFA exclusive, some others were even worse, up to recall of some ITT X-class caps that did fail with fire.I don't see a reason why a new cap from RIFA should be worse than from an other manufacturer. Time will tell in some 20 years which brand to fail more often.

author: Noy
author_rank: Frequent Contributor
timestamp: June 19, 2020, 10:50:09 am
content: Hm, i also have a Fluke8840A build 1998.Last time calibrated 2015 so pretty new.And it is bang in with my DMM Check Plus / Brymen 869s .I will save the calibration data from the eprom today / tomorrow and the Eprom Software. I will buy replacement eprom to store for "Bad Times".I'm mit sure If i should also so a recap. Especially cause of the bang on calibration. Could happen something worse which could destroy some of the "hard to get" parts of i will not do a recap?And cause of it looks like IT IS one of the later build fluke8840a ones. Is it necessary so "early" and with "good" calibration?

author: PixieDust
author_rank: Frequent Contributor
timestamp: June 20, 2020, 01:21:43 am
content: Quote from: Kleinstein on June 19, 2020, 09:13:13 amThanks, makes sense, I'll buy RIFA and be done with it.

author: pqass
author_rank: Super Contributor
timestamp: June 20, 2020, 02:56:32 am
content: FYI: Last month I replaced the 4 RIFA caps in my hp3478a with these:https://canada.newark.com/kemet/phe850ea4100ma01r17/capacitor-polypropylene-pp-film/dp/61M2387?ost=PHE850EA4100MA01R17https://canada.newark.com/kemet/r413i22200000m/capacitor-polypropylene-pp-film/dp/95M5296?ost=R413I22200000MThey met the specs, size, and were on sale (reduced price).

author: wizard69
author_rank: Super Contributor
timestamp: June 20, 2020, 03:22:17 am
content: I'm not sure if this timely for the original poster but not having a battery in a bench meter is worth at least $100 to me. Over the years I've had too many issues with batteries going bad, or in the case of alkaline leaking terribly. Of course not every battery used in electronics is alkaline but that doesn't mean the others will not go dead when you are not looking.Also if the meter doesn't support shrouded test leads I'd be concerned. On some meters this can be addressed easily, others not so easily. The big problem of course is the potential to have high voltages on those probe tips.