Help me with my new old HP 3456A - Page 1
Forum section: electronics / testgear

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: September 04, 2013, 06:57:20 pm
content: Hello everyone!I got myself a HP 3456A DVM on ebay for only $65 with shipping. In the picture it was displaying some numbers on the screen which looked about right considering with no leads just sitting there I had heard the voltage will float a bit. So I assumed it worked and bought it.Upon arrival at my home today, I unpackaged it and plugged it in after making sure the line voltage selector switches were configured properly and that there was no ovbious damage from shipping.Each time I turn it on, all I hear is a fan start up inside, nothing on the screen, no lights by the buttons, and all of the buttons seem to do nothing. I've tried leaving it on for about 5 minutes, and still nothing. Can anyone help me?

author: edavid
author_rank: Super Contributor
timestamp: September 04, 2013, 07:17:45 pm
content: If you believe it was working when shipped, the first thing is to look inside and see if a connector came loose.(Second thing is to check the power supply voltages.)

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: September 04, 2013, 07:29:38 pm
content: Quote from: edavid on September 04, 2013, 07:17:45 pmI actually just got finished putting it back together!I thought I'd take a little look inside, first thing I noticed while opening it is that most of the screws on the casing look like they were used A LOT and are almost stripped. But they still hold so I'm not worried.However when I got inside it I saw a screw was missing from the big shield that covers all of the boards, that screw I found floating around in the case, appearantly the threads are stripped so I replaced it with another screw.Under that shield I saw a huge board, about as big as a piece of paper had one corner lifted up higher than the rest. I looked down a connector near that corner and I did not see any gold plated pins poking through like I did on the rest of the connectors on the board, so I poped off the board and put it back in.I then turned the machine upside down to see if any other screws were bouncing around. When I did the board that connects with a ribbon cable to the front panel (probably the display) literally fell out of the machine, it's plastic fasteners were not inserted correctly, so I put that board back in and made sure all of the plastic clips were secured. I replaced the shield and top cover and powered it on and.....IT LIVES!!!Now I just need some help figuring out how to use it (the manual doesn't say much and all common sense showed me how to do is change to internal trigger, auto range, and the different measurements).

author: Unknown
author_rank: Unknown
timestamp: September 04, 2013, 07:36:28 pm
content: Switching functions is quite straightforward. I think the manual explains what 2W/4W ohms, ratio measurement and offset-compensated Ohms mean. One odd thing is that it comes up in 5.5 digit mode for some reason. 6 STORE NDIGS switches it to 6.5 digit mode. Changing the NPLC (sampling interval as multiple of the mains period) is another useful feature. That's the important stuff for bench use I think. It has other advanced features like math / stats that can come in handy, especially if you don't have a computer connected.

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: September 04, 2013, 07:46:03 pm
content: Quote from: alm on September 04, 2013, 07:36:28 pmYeah can you explain more about how many digits after the decimal place I could have for certain amounts of voltages and how I can make sure I get as many as I should? I was under the impression that I could get 6 after the decimal point, then after 1 volt I can have 5 places after the decimal point.EDIT: I tried pressing the number 6, then store, then the number 9 key, and it looks like it did increase the number of numbers displayed! Thanks!Yes I am also interested in changing the sampling rate, and maybe I'm mistaken but isn't there a way I could set this up to take and store measurements at certian times and then let me review them later?

author: PaulAm
author_rank: Frequent Contributor
timestamp: September 04, 2013, 07:57:20 pm
content: Download a manual, you can get a free one from Agilent. Another handy function is an offset. Take a reading, set it as an offset, then it will be subtracted from subsequent readings. Useful to zero out the lead resistance in 2 wire resistance checks.It's programmable through GPIB, so you can set up a computer to run it and log data.

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: September 04, 2013, 08:06:55 pm
content: Quote from: PaulAm on September 04, 2013, 07:57:20 pmI have downloaded the manual and I'll start going through it. And its good to know that I can get accurate 2W resistance checks considering that's all I know how to do.Hmm, how hard would it be to find some information on how to make a cable to connect this to a computer and what type of a connector would it connect to (serial? Parallel?)?

author: PaulAm
author_rank: Frequent Contributor
timestamp: September 04, 2013, 08:13:11 pm
content: You need a GPIB adapter and cable. Check out Prologix (http://prologix.biz/). They get good reviews on the hp_agilent group. You can go cheaper by finding a GPIB card on ebay, but what software you would use depends on your environment and how much of a software hacker you are. If you have big bucks or a student discount you could look at Labview

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: September 04, 2013, 08:18:01 pm
content: Quote from: PaulAm on September 04, 2013, 08:13:11 pmI'm not really willing to spend more than maybe $20 on this GPIB thing (hardware and software).Looks like it's quite a bit more expensive than that unfortunately...

author: Unknown
author_rank: Unknown
timestamp: September 04, 2013, 08:24:36 pm
content: That's not going to happen unless you find an old ISA card and a PC that still supports those. It's not hard to spend that just on an off-brand GPIB cable.

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: September 04, 2013, 08:27:12 pm
content: Quote from: alm on September 04, 2013, 08:24:36 pmWell I could easily get myself a cable, isa motherboard (and build the rest) and an isa gpib card for $100 but I don't really think that's worth it.Guess I'll just have to go without it....

author: PaulAm
author_rank: Frequent Contributor
timestamp: September 04, 2013, 08:29:32 pm
content: Unfortunately, GPIB sees a lot of use in ATE equipment; it's not a mass-market product and there's no real incentive to get the price down.People do put together automated setups on a shoestring, but it takes work. The cheapest cable I found recently still cost $10+shipping.You can find ISA cards in the $10-30 range if you look hard, but then you need an old 386/486 motherboard and a vintage OS as well. That can get painful.

author: Unknown
author_rank: Unknown
timestamp: September 04, 2013, 08:34:06 pm
content: The economics get better once you have several instruments with GPIB support. Although you still need one cable per instrument.

author: edavid
author_rank: Super Contributor
timestamp: September 04, 2013, 11:23:16 pm
content: There are also GPIB to RS232 and GPIB to Ethernet devices that turn up for low prices, but if you just want to do some simple data logging, it's probably not the best way to go.Hope you find some good uses for your HP 3456A... but if not, you could flip it and buy a Chinese DMM with a USB interface.

author: lowimpedance
author_rank: Super Contributor
timestamp: September 04, 2013, 11:44:23 pm
content: You mentioned the unit had a fan, this would make it one of the early versions. I would highly recommend you check the power supply PCB electrolytics and replace as needed.These meters are very robust and long lived but the PS electro's do age. Search the forum, there is plenty enough threads about these meters.

author: macboy
author_rank: Super Contributor
timestamp: September 05, 2013, 06:33:09 pm
content: Quote from: PaulAm on September 04, 2013, 08:29:32 pmI have an ISA GPIB card in a P4 system running WinXP. It is 3.06 GHz with 2 GB DDR RAM. That is one of the highest spec ISA compatible machines you can get. The motherboard is an Intel-made industrial board, pulled from a kiosk of some kind. I put this together a couple years ago when PCI GPIB cards and USB adapters were still extremely expensive. Now for <$100 you can get a brand name PCI GPIB card or a Chinese clone of a Agilent USB GPIB adapter.I use NI cwgpib activex controls within my custom-made HTML Application (HTA). Using an HTA means that you can make a decent GUI using only html, and you don't need any development environment other than a text or html editor. Zero cost.

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: September 05, 2013, 06:48:59 pm
content: I was reading the manual last night and figured out I could store over 300 readings on the meter iteslf without a pc, so I'm not going to spend a dime on GPIB.This multimeter is massive overkill for anything I do but wow it is an awesome piece of equipment to have!