34401a or 34461a or SDM3055 for the bench - Page 1
Forum section: electronics / testgear

author: Bryan
author_rank: Frequent Contributor
timestamp: September 18, 2015, 05:49:59 am
content: Hi All:Looking for opinions. Just a general hobbyist that has dabbled in electronics on and off for many years. Have always wanted a nice bench DMM so was thinking of throwing some money down. Honestly, probably a Fluke 87V is all I really need for what I am testing and the tinkering I do, but I have my heart set on purchasing a bench DMM. I originally thought of a good used 34401A. They are well proven with a excellent track record, but long in the tooth. However with the exchange rate, and the likelihood it may need a calibration, for the same price I can get a brand new Siglent SDM3055. Yes I know it is a bit buggy and slow and only a 5 1/2 digit, although from the videos and reviews I have watched it really doesn't seem like something that would concern me as a hobbyist. Perhaps yes if I was in a shop or it was to be used on a production line. Seems the firmware updates that have been coming along are starting to address some of these issues.I am getting rid of some other equipment and I could afford a Keysight 34461A, but that is a expensive piece of equipment, very nice but likely overkill for what I need. At that price I could get myself a SDM3055, replace my Rigol DS1022E with DS1054Z and probably still lot's left over for something else for the bench.Hmm...

author: TheSteve
author_rank: Unknown
timestamp: September 18, 2015, 06:04:56 am
content: A Keithley 2000 or 2015 might also be something to consider - especially if you can find a deal on one. I'd prefer a used(but 100% operational) 34401A over the Siglent.I was in the market for a 34401A myself but was given a Keithley 2001 - also 20 years old.And you can never go wrong with a Fluke 87V for a portable use/second meter, especially if you can find a deal on a used one locally off CL/Kijiji.

author: bitseeker
author_rank: Super Contributor
timestamp: September 18, 2015, 06:23:01 am
content: I like both the HP 34401A and the Keithley 2001. However, I went with the HP because the old Keithleys are rather notorious for having capacitors leak and damage the PCB. If you get a Keithley 2000-series meter, open it up and replace the caps, pronto.

author: dkozel
author_rank: Regular Contributor
timestamp: September 18, 2015, 07:08:18 am
content: I can attest that currently on the forum there are offers available for the 34401A and Keithley 2000 comfortably below the price of a SDM3055, some in the US. They look to be in very good condition and I've found a pair, one of each, with calibrations in the last three years.The USB or LAN on the Siglent is nice, very convenient, but you can easily add an RS232 to USB adapter to get going. Also think of the ecosystem. HP-Agilent-Keysight provide Benchvue for free and the 34401A is supported. That's a nice, modern GUI with logging and statistical analysis. I'm sure that software will mature or gain support for the Siglent because it does look like a nice unit, but I was more comfortable going with a unit with broad support and a long history of stability. The designs are old, but both are currently manufactured.My thought process, hope it's helpful.

author: deadlylover
author_rank: Frequent Contributor
timestamp: September 18, 2015, 08:14:06 am
content: If you have a PC on your bench and can use benchvue(+ don't mind the hassle), then the 34401A is real hard to beat in terms of value. You can start getting a bit volt-nuts once you have a taste of ppm-level resolution, you have been warned...Just a few tips on looking at a 34401A;It defaults to 5.5digit mode on power-on, so if the pictures don't show it in 6.5digit mode, there is a chance the final digit will be noticeably brighter than the rest. On that note, after a certain serial number you cannot use the current front panel assembly as a replacement (so you may have to transplant the VFD instead), it's buried in one of the service notes somewhere and has something to do with the firmware.The factory cal count is around 35, so if it's higher than that then you know it's been adjusted/tinkered with. Having said that, I do have some old HP units that haven't been adjusted and they are mostly still within 1 year spec, it's usually the current ranges that drift out first.

author: engineergorman
author_rank: Newbie
timestamp: September 18, 2015, 10:10:23 am
content: I bought a nice HP 3478A for $125 (including ship) on ebay for my first bench meter (you can get them cheaper, perhaps around $75 if you are patient). I really like it a lot. Very fast measurements in 5 1/2 mode (insane fast at 4 1/2). Had to change out the internal calibration memory backup battery though, but that was actually quite fun (and excellent info on this forum regarding that). I lost the calibration constants because of a solder bridge though.Build quality of these older HP meters are excellent... super clean. Dave has a teardown video of one. I don't mind the LCD display at all. It's super easy to read if you have decent light on your bench (although I do prefer the VFD displays of the 34401A).Since I screwed the cal on the 3478 I decided to buy an HP 34401A that was calibrated and use it as a transfer standard. I learned a lot in the process, i.e. how to build low noise, stable, adjustable voltage and current references. Oh, then I started playing around with the SCPI interface (via RS232 -> USB converter) using Putty as the terminal. That was a mistake.There is something really fun about sending simple text commands to the meter and seeing the results come back. I liked the simplicity of it... knowing that if I need to do a simple measurement in the future I won't have to rely on installing IVI drivers and an SDK, dealing with possible driver bugs, OEMs going out of business and not supporting the software stack for my current OS, etc... because it's just plain ascii text. And the SCPI commands are superbly documented in the 34401A user manual. I wouldn't recommend IVI libraries if you didn't need the abstraction layer. I wrote a tiny SCPI interface layer in C# that is about 50 or so lines long... will post on github in a few days. I liked everything about the 34401A so much that I ended up buying 3 more.I played around with free version of benchview and noticed that there is a time limit (30 mins?) on how long you can log data... to go longer you have to pay for an upgrade. I think the upgrade price was reasonable though, and the software was nice. something to keep in mind though.I have been very happy with the 34401A and the 3478A. But if you wanted to save some money, and didn't want or need the logging ability, you could go with one or two HP 3478A's and maybe have spare change.

author: Bryan
author_rank: Frequent Contributor
timestamp: September 19, 2015, 08:51:27 am
content: Quote from: TheSteve on September 18, 2015, 06:04:56 amTrue, but the challenge is trying to find a good used one. Lot's on Ebay, but I have often seen the same DMM go up for sale multiple times, most likely a dud. Seems there are many with minor issues but still useable. Seems a good used on with a current cal sticker is going to run about $500.00 US. The current currency exchange is a killer.