Based on teardown photos on EEVblog, 8588A does not use LTFLU but LTZ1000 instead.
Old batch 8508As also used LTZ1000 (exact module from 1281/1271) before switching over to LTFLU. On October 26, 2019 4:09:09 PM EDT, Frank Stellmach <[email protected]> wrote: >Hi Philipp, > >you definitely have to clean the fan filter of your unit.. standing >free >on a table, and with a clean filter, the internal temperature rise is >12..13°C at most. > >Defining a metrology grade 3458A would explicitly require to define and > >control the environmental conditions in the specification, like >reduced >temperature range, specifying the ventilation requirements, like no use > >in a rack, by using a different filter, and also by regularly checking >the internal temperature by firmware. > >The 3458A is designed and specified as a system DMM, inside a rack, in >a >hot manufacturing environment, like in a electronics manufacturing >line, >but never was intended and built as a metrology DMM, as hp and KS still > >try to advertise. > >Your argument, that a sample distribution is root cause of these wide >specification limits, does not convince me: > >The annual and temperature drift (with ACAL) is mainly determined by >the >drift of the two internal references, due to the ACAL technique, the >rest of the circuit does contribute only marginally, but on the w/o >ACAL >specifications . > >Therefore, the 8508/88A simply beat the 3458A, because they use an >LTFLU >running at 45..55°C only, instead of 95°C, and due to the heavy usage >of >stable Vishay BMF resistors, which also contribute to the superior >short- and midterm stability of these instruments. > >So only the sample distribution and yield of the LTZ and 40k resistor >affect the annual drift specification limits for the 3458A. > >Concerning the LTZ reference, that is already covered by their >monitoring / selection process, where they have for sure have yield >problems already. > >If they would simply reduce the temperature for metrology purposes, >like >in practice done on the FLUKE DMMs, they would directly get near 100% >yield for 2..3ppm/year (@65°C), due to the ACAL DCV feature.. > >The 8508/88 on the other hand have to account for the drift of other >components, to achieve e.g. these 4ppm/year, although the LTFLU very >probably performs more like 1..2ppm/year (inside the 732B, @ 47°C, for >example). > >I think the 3458A would at least be on par with the FLUKE DMMs if KS >would simply chose the same metrology grade resistors and oven >temperature as DATRON/FLUKE had done... > >Frank > > >_______________________________________________ >volt-nuts mailing list -- [email protected] >To unsubscribe, go to >http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com >and follow the instructions there. BR, Illya Tsemenko _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there.
