Fluke 5450A cal result - Page 1
Forum section: electronics / general

author: VintageNut
author_rank: Frequent Contributor
timestamp: March 01, 2017, 06:25:07 pm
content: This week I have access to a primary cal lab. My 5450A has been calibrated. I am sharing the results for the community here to view and make comments if desired.The calibration used two MI bridges. My understanding is that the low ohms up to 10K uses a current comparator bridge. The values over 10K uses a voltage comparator bridge. There is a temp controlled pool with a Thomas 1 ohm in the pool.

author: CalMachine
author_rank: Frequent Contributor
timestamp: March 01, 2017, 06:41:06 pm
content: Where is this lab located? That's a damn good uncertainty! 5 ppm @ 100 MOhm...

author: e61_phil
author_rank: Frequent Contributor
timestamp: March 01, 2017, 08:22:43 pm
content: Was this the first calibration or do you have some experience with the drift of a 5450A?

author: VintageNut
author_rank: Frequent Contributor
timestamp: March 02, 2017, 01:09:03 am
content: Quote from: e61_phil on March 01, 2017, 08:22:43 pmI bought this 5450A from eBay a year or so ago. This is the first calibration under my ownership with no history of previous calibrations.My plan is to have this calibrated once a year if possible.The technician who performed the calibration said that it requires about 30 minutes per resistance. He spent an entire day calibrating the box. No way I could afford this if I was paying for it. The calibration was performed as a favor.They are also calibrating my two 731Bs and the three high resistance bricks that I assembled.When I get home, I can go crazy doing some bridge measurements with one or more of my DV4107 KVDs. Woohoo

author: Dr. Frank
author_rank: Super Contributor
timestamp: March 02, 2017, 06:39:51 am
content: The regular calibration process won't take a whole day, so I really wonder why it took the cal lab guy so long.I also doubt, that this very low uncertainty certification of calibration is useful, as the resistors inside the 5450A are much less stable in time and temperature.There's also that probable leakage problem with the electro-mechanical relays, which will falsify the calibration of the higher resistors, from 100k to 100M.This (error - checking)validationverification has been omitted by the cal lab, as they did not follow the intended procedure.Did you attempt to calibrate the 5450A on your own, so tovalidateverify the regular calibration constants versus the measured ones?FrankPS: Judging from the date codes inside your box, how old is your 5450A?PPS: Adding link to my findings on error during the calibration of the 5450A:https://www.eevblog.com/forum/blog/eevblog-544-fluke-5450a-resistance-calibrator-teardown/msg1113471/#msg1113471

author: ap
author_rank: Frequent Contributor
timestamp: March 02, 2017, 07:41:29 am
content: The reason these measurements take long (total time per resistor) is temperature settling and multiple measurements per resistor to build average with the MI bridges, this way you can achieve this accuracy. If all this makes sense for that unit is truely questionable, given its instability. It would have been much more valuable, having acccess to such accuracy that cheap, to use a set of precision hermetic resistors with low drift. Not sure what the 5450 has cost, but probably in the same range as a set of such resistors from VPG.I have my 732 calibrated to 0.3ppm, and they do it over a couple of hours in a tightly controlled ambient, somehow justifying the price.

author: aronake
author_rank: Frequent Contributor
timestamp: November 25, 2023, 07:03:25 am
content: Quote from: VintageNut on March 02, 2017, 01:09:03 amDid you ever get this calibrated again? Would be interesting to see drift.

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: November 02, 2024, 02:31:42 am
content: Quote from: ap on March 02, 2017, 07:41:29 amI think you are wrong. A Fluke 5450A will outperform a single off-the-shelf Vishay resistor in terms of drift. You can't buy the same amount of Vishays VHP101s needed to compete with the Fluke. The resistors used in the Fluke 5450A are similar to the 742A and other high-end calibration equipment.This isn't debatable.EDIT:Apparently, it is debatable! I would argue that the Fluke 5450A is an amazing option. If you want high stability, a Fluke 742A is hard to beat. If you have 2,500 $ to spend, get 25x Vishay VHP101s.