In the Mkt for a HP Bench DMM

One opinion: I really like the 3478A. I bought a 34401A (not 33401A, dunno what that is) when it came out, and it's certainly a great DMM. Then a friend won a couple of 3478A auctions for around $200 each and brought them by my bench for calibration against my (still-relatively- new) 34401A. Our conclusion was that the 3478A is 95% of the meter for

I very rarely use the 34401A's extra digit, or any of the other minor features that distinguish it from the 3478A. I do prefer its vacuum- fluorescent display to the 3478A's LCD... but it ain't worth an extra $400.

Both DMMs are great instruments, but the bang-for-the-buck prize goes to the 3478A by a mile.

-- john KE5FX

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Thanks. Sorry for the typo - 34401A.

There are others similar to the 3478A that have a VFD or LED display, but may be older.

If you would be willing to stoop to a mere 4-1/2 digits, I have some

These are very nice little modular desktop units which have more accuracy than most of use will ever need, plus once you have the display, you can also buy a plugon frequency counter. There are a number of counter modules available to cover the range from 10 MHz to

I have a text file describing each of the modules. I will be glad to send you a copy if you are interested.

If you really want 5-1/2 digits, I have some 34650s which are that wide, but they are more expensive and don't have the frequency counter capability. They also consist of a display and your choice of plugons.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Thanks, but I already have a Fluke 4-1/2 digit DMM. Tnis morning on Ebay I missed a chance to bid on a HP 3478A and it sold for $75. Darn!

Being as it comes from Tucker, I'll let you know if it works.

-Chuck

If you can forgo HP, these come up for auction now and then at a good price:

This one is priced ridiculously high; I've seen them to go for $100 to $150 with GPIB. I purchased one on Ebay for $145, and I'm quite happy with it.

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When i saw the price on the one in the URL I was kind of hoping that they would be available for a more reasonable price. One thing I'm concerned about is availability. If they're a lot less common than the HPs, then I'm guessing that they might be in greater demand, and hence command a higher average price. And then there are the manuals and stuff. I see the manuals (on CD) for the HP 3478A going for under ten bucks. Maybe more for the originals on paper. Are the manuals for the PM2534 going for about the same, or do I have to pay $50 for them? I'd really like to have them. I got the manual for my old Fluke 8600, and when it blew a +-15V regulator chip, I was really glad to have the manual and be prepared.

I also saw a few models of Keithley DMMs I thought might also be good choices. I'm wondering why the two names Philips and Fluke are associated. I'm guessing that since Philips is sucn a huge international organization, that they're actually the manufacturer, and Fluke markets them in the U.S. and possibly calibrates and services them, possibly for the whole world. Fluke is an older, well respected org, but nowhere near as big as HP or Philips.

I had the same concern when I bought my PM2534, but at that price I couldn't resist. Anyways, after getting the meter I posted that I was looking for one, and a kind soul scanned and emailed me one within a few days. It didn't come with a four wire probe but the service/operators manual showed the pinouts, so I was able to build my own. If you do end up getting one, shoot me an email and I'll send it to you. It even has the schematics. My email address is jwalling at comarkcorp dot com.

IIRC, I think they collaborated for a few years back in the 80's. The sticker on the top reads "Fluke and Philips the T&M alliance".

Regarding my $75 HP3478A from Tucker, by way of eBay: It is perfect!

Tucker treated the unit like it was a $750 DMM. It was sent FedEX, and arrived in 3 days. It was in a brand new, tucker branded, oversized box, and was foamed-in-place. It came with a bound xerox copy of the operator's manual, and a 5 day trial period.

The unit had several callibration/inventory stickers, on it, but none of that nasty permanent felt tip pen that the US Gov't defaces its surplus with.

I got lucky! I will buy from Tucker again, if the opportunity arises.

My only regret is I forgot that the HP3478A has a reduced measurement range. It is only 300V full scale! Why did they do that?

-Chuck

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Thanks for the info. Some possibilities are.. The precision resistors don't come in high wattages so the V dividers can't handle more than

If HP or some other company offers a V divider probe, then 10:1 division would up the maximum measurement to at least a kV. But I think 750V is kind of pushing it. I have a 'heavily used' Fluke 23 that the HVAC guy gave me at work. It powers up and displays but any input doesn't cause any reading - just 0. I think he used it on 480VAC or something high like that and it burned out. I hate to throw it out because someday I might find another with a bad LCD display and I could make one good one out of two bad ones. :-)

Speaking of LCDs.. Some of our digital phones have a LCD. On occasion we will have to replace one that has gone black. I think it's caused by the hot sun hitting the display. So it's probably a really bad idea to leave your DMM near a window where it might be exposed to the sunlight. I just wonder how the car makers keep the LCDs in the instrument cluster from getting overheated.

They seemed to be able to do 1200V on the HP3438A, which is a distant predecessor to the 3478A. (3-1/2 digits, led, HPIB, autoranging, smaller too!)

Crack it open, if it was blasted with HV, the problem should be obvious. Not necessarily fixable, but obvious. The basic meter circuits will be protected by a pair of diodes (head to tail, in parallel). There is usually a sacrificial part, or 3, before the diodes.

Heat turns them black while hot, but they should return to clear once they cool. The car manufacturers are obviously using a LCD technology that handles heat gracefully. Undoubtedly a byproduct of the military.

I have found that dropping an LCD display can turn it black. What happens is the seal cracks, and provides a polarization shift that the polar filter shows up as black.... still toast, though.

-Chuck

If you don't mind an older unit look at the HP 3456A. It was "the" standard in its day. It is 6 1/2 digit and very accurate. HP doesn't support it any longer but then if you are paying a hundred to two hundred for a meter you wouldn't want to send it to HP for repair anyway. Their repair cost would far exceed that price.

The 3566A can be found for around $100.00 to $150.00. They are strictly a bench meter though. Quite large and heavy.

The HP 3455A is also nice but not quite the accuracy as the 3456A but the AC measurement frequency goes higher.

Another meter to look at it the Fluke 8840A. It is 5 1/2 digit. Very nice. Only problem is they usually don't come with the AC converter board in them. (option 9)

The fluke 8502A is another good one to look at. It is older but very accurate. Have to watch what comes in it though as the AC converter and even ohms board were options.

The Fluke 8506A is equivalent to the HP 3456A but better AC than the HP.

If you can live with 4 1/2 digits the HP 3466A is a bargain. They can be had for well under $100.00. .03% accuracy on DC.

Another good inexpensive 4 1/2 meter is the Fluke 8050A. They are also .03%. Can be had for under $50.00. They have some nice features like offset with one button and will read DB relative etc. Only bad part is it is not auto ranging.

I also picked up a Keithley 197 for well under $100.00. It is the same as the 197A but has no back light and less battery life if you use it on battery. Other wise they are the same. 5 1/2 digit .015%. Not quite as stable as the Fluke meters or the HP. The keithley takes awhile to stop drifting but it is not bad. You would never know unless you compare it to a meter like the HP3456A.

These are all older meters but they can be picked up at a very bargain price. If they break you will have to fix them yourself. In that case you may find a spare for parts. Those are cheap too.

You can look on Tuckers web site and find the specs on most all these meters.

Thanks for all the good info. I found a single 3478A on Tucker's website and it was $795 so I don't think I'll be back there soon.

In the last wk I've seen the 3478A go for anywhere from $75 to $220 on ebay, most are well over a hundred. I'm still waiting for another one to come for bid at a reasonable price. Right now someone has one for sale, but this is like his first sale, and I don't think anyone wants to put very much money up for bid because he may be just a fraudster.

Not to go off topic, but last year, auction fraud was one of the top ten frauds - usually in the top 3 - reported to the consumer sentinel. It never hurts to be a little overcautious.

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I wonder why tucker let me have mine for so cheap? Cheap isn't usually their thing. When I was buying and selling a lot of surplus, I would use

I think the odds of this guy being a fraud are reasonably large. His presentation is very polished, and is full of contractual terms that aren't likely to have occurred to a first time seller. I would think it is more likely that he has sold a lot on ebay, but has changed his account name for some reason.

If I were truly interested in this unit, I would contact him, and ask him why the low seller number... and what was his previous id. His answer might allow you to bid.

-Chuck

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Yeah, I hear you.

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Trouble is that he could tell me 'I used to be joeblow' and if I tried to find out anything on Ebay, I would just get a 'no longer a valid ID' or something like that. He could've been a crook but w/o info from Ebay, no one will know.

But he could have had previous experience on another site like Yahoo Auction. He might be experienced, but new to Ebay. But your scenario seems to be a lot more likely.

One othe thought. He could've been an employee of another experienced seller and has decided to go out on his own.

One thing that I've noticed about Ebayers is that the IDs they use seldom reflect their business or real name.

That's one of the main things I didn't like about my HP3478As. I found the (relatively) small LCD display difficult to see.

My favorite bench meter is the Fluke 8506A, followed by the HP3456A. They are full rack width instruments, but the bright red LED displays make them way easier to see than the HP3478A. The Fluke 8506A's super large LEDs are especially easy to see.

I confess to using a handheld Fluke 87 III more than any of them. It does what I need, has large LCD digits, and its small size lets me use it anywhere. If I could keep only one DMM, it would this one.

I am like you Bob, I have a Fluke 87 lll that I use most of the time too. Very handy and dependable. When I need higher accuracy I fire up the HP 3456A. Setting power supplies in test equipment or calibrating other meters etc. It has some nice math functions that are handy sometimes too. Another thing that is nice abut the 3456A that people don't think about too often is the input impedance. It has 10 to the

The Fluke 87 lll and similar meters are 10 meg ohm input resistance on all ranges. The high input resistance on the 3456A and those type meters are handy some times. I have a Fluke voltage reference that requires a high input meter in order to read it. Or you other wise must use another reference and a null meter. Most references can not be read with a 10 megohm meter.

The ohm meter on the 3456A will read to 1 gig ohm. Handy sometimes.

Warm-up drift is excellent on the 3456A.

How about these? They are available with a variety of VOM plugons with various capabilities. I haven't sold one of these before, but I have them all fixed up and calibrated. They are old, but they seem to work quite well once I get the bugs out.

The price would depend on the plugon that you wanted with it. What kind of measuring capabilities are you after?

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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Well, a few minutes before it ended, I bid on a HP 3478A DMM, and no one else bid on it, so I won, for $75.00. It's from Teoutlet, which is Tucker. I gotta wait for them to contact me for some reason, because they have to charge me for sales tax because I live in Calif. It's something less than six bucks, With shipping, it'll come to somewhat under a hundred. At that price, I could buy another and have a spare. ;-)

So now I gotta get some manuals, and I'd really like some 4-wire test probes. I've never seen them, but knowing HP and the likes, a new set will probably cost a lot.

But here's the question I hinted at a while back, that I was gonna ask. I think I might've run across something like this when I did a search for Keithley stuff on Ebay. What I wonder is how do I automate a test jig. I took a double pole, 6 position rotary switch and mounted it and some terminal strips to a piece of wood. I can then connect my DMM to the wipers, so I can then run wires to the different test points on the jig and then just turn the rotary switch to whatever place I want to measure. I would guess that there is something similar, but all electronic from somewhere. I don't remember ever seeing anything like it from HP or Fluke. I think Keithley may have something like it, tho. A bunch of relays with driver transistors could be connected to a parallel port and controlled by a program on a PC.