First Bench Multimeter - Fluke 8840a vs HP 3478a

[pqass]

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.

Depending 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: 

[pqass]

HP 3478A is line switchable, you'll have to open it up to do so.

Video from VoltLog on the subject:

Thanks, great link.

Does anyone also know whether this HP 3478A can measure voltage and current at the same time?

Sadly, no.

[J-R]

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.

[coromonadalix]

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.

[pqass]

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.  :-)

[J-R]

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...

[J-R]

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.

[nctnico]

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.

Well, sure you could always spend more to get more features. 

That 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.

[PixieDust]

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?

[pqass]

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?

Correct.   

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

[PixieDust]

Ah awesome, thanks for the link!

[pqass]

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...

Don'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).

[PixieDust]

How are these units calibrated (HP 3478)? Over GPIB?

[pqass]

How are these units calibrated (HP 3478)? Over GPIB?

Through 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

[gryffinwings]

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.

[gryffinwings]

Any recommendations on some test leads, since this one doesn't come with any?

[J-R]

Looks like it needs non-shrouded...

[PixieDust]

Any recommendations on some test leads, since this one doesn't come with any?

Apparently Pomona is the brand that supplies leads to Fluke. They have silicone casing which means they'll last decades.

[pqass]

Any recommendations on some test leads, since this one doesn't come with any?

Shrouded 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.

[AVGresponding]

Pomona make rectractable shroud leads, 6366 is the model I think?

[J-R]

Well, if you don't mind cutting:

https://www.ebay.com/itm/Agilent-HP-Keysight-5180-6661-Standard-Lead-Set-34132-37904-NEW/283738612273

If you want the ones with the HP logo, be sure to talk to the seller first or you may get Agilent.

[GreyWoolfe]

You can get Probemaster 8010S leads without shrouds and they are fairly cheap-$19.

[wizard69]

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.

Very 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.

[gryffinwings]

Pomona make rectractable shroud leads, 6366 is the model I think?

These ended up being the best deal, so I have them on order.

[PixieDust]

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?