I totally agree with
TiN.
Only few hobby people can take the risk and buy a cheap 3458a (still 2K€!). Those are the people who have a Lab Cal in the apartment, and have a LOT of knowledge in Metrology.
They can know if the 3458a is a titanic wreck or not, and after at least of some days or logging. Moreover they know if it makes sense to repair it or not.
A simple post here it's not enough sorry. I tend to say in Metrology a simple post is never enough. Metrology is very complicated and require a lot of expensive toys.
OR you are like me and you want to invest money on yourself and your education.
See, I bought a cheap used K DMM7510 (2400€! sooo cheap uh?),
https://www.eevblog.com/forum/buysellwanted/keithley-dmm7510-(not-mine)-ebay-(nleu)/and not sure yet if it works correctly. Yes it looks good outside and pass all the selftest. It measure ca. 230VAC at the mains and it doesn't smoke. My ref R decade also agrees with the meter R in 2W mode. Well does it drift or not, how stable it is? Is everythining spec.? Dont't F know.
Now I have finally to take out the 7V Ref I bought from
TiN in 2015
! https://www.eevblog.com/forum/buysellwanted/(fs)-2-x-ltz1000(a)-ultra-zener-voltage-reference-sale-direct-output/msg624718/#msg624718and I will start to learn what does it means the ppm stability, maybe raspi log (T and RH) stuff and so on. I want to learn how the stability change when the reference is protected form air, allan deviation? I want to touch with my hands the 1/f noise best spot claimed by the K Rnd at NPLC 5... you name it.
It's an expensive game, but it's so interesting and so eyes opening.
PS: I still have a dismantled silly K2001 in two boxes. I want to improve stability by replacing the the zener Vref, why? I want to learn and see why the K engineers decided to put on the market a DMM with higher noise specs (compare to the K2000). Unique thing in K2001 (as I know) there are 2 Vref inside the K2001 which are somehow connected togheter, and the schematics are there. Perfect territory for me to learn.
And at the end what is blocking me? time, F time! This year I was/am on business trip for 5 months, I am preparing two ironman triathlons and the EE lab comes after that... so sad.
Thank you EEVBlog, TiN, Kleinstein, Dr. Frank, ManateeMafia, High Voltage and all the others Metrology doctors here. You are keeping my EE desire to learn awake.
PSS: I know too many projetcs in parallel.. that's me sorry.