A dream came true Today34401A Digital Multimeter, 6½ Digit DMM

[coromonadalix]

you have some software(s) who will give this old veteran life extension   lolll

[jerryk1234]

I just got one of these yesterday.  Normal Ebay price.  What a gorgeous meter!  The sixth digit is very slightly brighter than the rest.  I ordered a new display.  Not so much because it's dim, rather to have a spare 10 years down the road.  Out of the box, it agrees closely with my Fluke 87V.  That's good enough for me; my repair and experimentation activities don't require extreme accuracy.

[DavidAzulay5000]

Testing 4 wire kevin sens cable thet I built
with my HP 34401A
with power resistor 10 milliohm
spot on

[nukie]

The first stop after I fixed all my used 34401A is the cal lab. Even just simple capacitor refresh. You never know what the equipment went through and they could have done repairs to the devices. Soldering can change alot of things especially with these precision equipment.

I have done some repairs to a few 34401A and I find even replacing the tantalum caps near the opamps pins can sometimes throw the calibration off the charts.

If you are certain that your equipment is good and want extra assurance you can always rent another 34401A from a reputable test equipment hire. They usually have yearly calibration done on them. If you are lucky it could be done recently. Then you can compare your equipment with the rented dmm.

[deepfryed]

I recently acquired one of these in good condition, but cost a fair bit more though - closer to A$650 

It does seem to agree with the precision resistor (0.005%, 0.2ppm/c) and reference (max6350 without trimming, 0.02%, 1ppm/c) I have (not calibrated), but as people have said can't be sure until it's calibrated. I'm not sure if it's purely coincidence or both the reference and resistor have the same error as the DMM 

The DMM cal menu says it was last calibrated in 1996, again don't know if people really update it.

I'd like to double check the "standards" I have if possible but don't want to spend another $200 on calibration / adjustment!  Is there a metrology group in Melbourne ?

[deepfryed]

I made myself a usbgpib adapter (https://github.com/xyphro/UsbGpib) and use the python-usbtmc library to read remotely. I can write something quickly to graph in realtime if necessary.

1000 readings/s is more than enough for my hobby needs.

[rhb]

The AR488 will take care of logging.  For hobby cal, join the USA cal club round 3.  I logged both my 34401As for several days in round 2 against the excellent voltage references that @TiN designed and built.

The  most heavily used  unit had been calibrated  about a dozen times.  The new looking unit had never been cal'd.  Extensive checks with limited kit showed them in spec for everything I could test.

Going price for a 34401A in NA is $325-$350.  3478A is $125.  That's both ebay and the test equipment lists on groups.io.  The 34401A may lack some convenience features, but the price-performance of the 34401A and 3478A can't be beat for reliability, accuracy and ease of repair or replacement.

Have Fun!
Reg

[Veteran68]

I have an Agilent 34401A (newer generation of the HP with black+red probe connectors) purchased from a member here on eevBlog for $250 just a few years back. Excellent condition and per my hobbyist references is still well within spec and plenty accurate for me. If I had a local cal lab I'd like to get it calibrated, but calibration will cost more than I paid for meter, especially if I have to ship it somewhere. I consider it probably my greatest bargain find in this hobby. While I do plan to pick up a Siglent SDM3065 to have the newer features, I will keep this one. It's fast, has a nostalgia factor and there's just something sexy about a VFD! Plus you know what they say: two is one, and one is none.

And do I *NEED* 6.5 digits for my hobby use? Not really, but I have a compulsion to get the best I can reasonably afford. I consider a good DMM to be the heart of any electronics bench and it's nice to know I have the extra precision should I ever need it. And I also have over a dozen handhelds ranging from higher end Fluke, Brymen, and Hioki to Uni-T, Aneng/Zotec, and Kaiweets (yes, I have a problem, I can't stop buying meters!). I've cut corners on a cheaper scope (not going to spend thousands for one when I seldom use it) and SigGen/AWG, but not my main DMM.