Thanks again, I've downloaded the manuals on most of the HP DMM's from that era. I'm now looking at the 3456 or 3457. I've got some prices on a cal and yes around $140 should do it for a NIST traceable cal plus shipping. Of the two meters, 3456 or 3457 which would be the smarter purchase ? The issues with the batteries I'm well aware of. My Tek 2465BDM lost it's Dallas chip internal battery. I've had to recal it after replacing the chip. A process that takes a while. It's accurate within about 0.1%. Good enough for a scope. The DMM is not anywhere near it's rated cal of 0.03% due to the data loss.
In the interest of saving space I'm also looking at the HP 3468a or 3479a. I'm not seeing a major difference between the two except for perhaps some lower ranges on the 3478a. Any helpful info regarding those devices.
If I can score a 3456a or 3457a for a reasonable price then I'll be heading that direction. At the moment I'm stuck doing projects with 4,000 count B&K meters and a 20,000 DMM on the Tek 2465 which is not in cal to it's spec. So my purchases will be pretty soon. I have a Fluke 8010 on the way which I'm sure will also need cal.
Thanks,
Jeff
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On 12/23/2012 7:08 AM, marvgozum wrote:
You're welcome, and all, enjoy the holidays. It may pay to download the 1993 HP Catalog, that was the last year all in the 345x line were available for sale, so you can compare and contrast the specs, also against the 3478.
The HP manuals, Keithley handbook and the volt-nuts archives are free, just download and search as needed, so you can get all the basic cal and operations info without cost to your misses before you actually buy something ;)
If you intend to stack a lot of gear ontop the 3456a and not sure about weight, put a 2x4 plank so weight get distributed to the edges of the chassis, this is were the most strength lies, while the top and bottom chassis covers are the weakest as there is also no cross bar for structural support. The plank allows a gap for added cooling, even if vents on the 3456a are on the sides and rear, the plank method works for all rack mounted sized gear.
As always too, heavies are best at the bottom, light at the top, as often the boat anchors are also made with stronger chassis to take not just its own weight but others too.
Lastly, I'm not a fan of designs that use battery backed up SRAM for system data, I prefer EEPROM at the least. Since all your purchases are used, the state of the battery is unknown and should be replaced, ASAP. If it snafus, or worst just corrupted, such as in buying "CANNOT TEST" "AS IS" type eBay gear, you'll need budget the possibility of adding $100-140 to your purchase cost to get it formally recalibrated.
With the 3456a, the all pots method puts the user in full control of its cal state, you can cal any range, any time [ keeping metrology guidelines in mind], so if you get one working or not, its also much easier to repair to working order entirely by yourself.
--- In hp_agilent_equipment@... <mailto:hp_agilent_equipment%40yahoogroups.com>, Jeff Machesky <jeff@...> wrote:
I have to say this response has really given me the most food for
thought. It provided exact details about the models and the pro's and
con's of each. It also made me realize something important. There is no
reason I have to buy one of these devices and run out and get it
calibrated. I can make sure it's readings are within reason and take it
out later on to get it calibrated. My main goal is resolution, so I can
have that now and have the accuracy and the resolution later. It will
also give me time to clean up and gain confidence in the device before
spending more money on it.
Very good feedback, Thanks.
Jeff
