Vishay will sell direct in single units any value/tolerance in their precision bulk foil resistor range.
There's a non-trivial lead time but ... David -----Original Message----- From: volt-nuts [mailto:[email protected]] On Behalf Of Dr. David Kirkby Sent: 30 June 2019 19:06 To: Discussion of precise voltage measurement Cc: [email protected] Subject: Re: [volt-nuts] How should I clean a 400 k ohm resistor? n Sun, 30 Jun 2019 at 12:40, Nigel Clarke via volt-nuts < [email protected]> wrote: > Hi David, > Many thanks for your notes re the ICs and and for the version 12 firmware, > I'm still undecided as to whether or not I'll perform the firmware update > anyway but it's certainly good to have the choice. > With regards to the 400K resistor replacement, the HP service note on > replacing this doesn't include any instructions for cleaning and the only > "burn-in" requirement is to leave the unit running for four hours before > calibration, so presumably that's all you'd get if the replacement was > carried out by Keysight themselves.Obviously it doesn't hurt to improve on > the minimum but I would expect that careful cleaning of the component and > rework area with 99% isopropyl alcohol should be adequate followed by > burn-in as suggested, then keep an ongoing eye on the calibration. > Nigel, GM8PZR > I did not notice the 4-hour burn in period. That makes life a lot easier. I thought about buying one of these Caddock USF370-10.0M-0.01%-5PPM resistors https://www.digikey.co.uk/product-detail/en/caddock-electronics-inc/USF370-1 0.0M-0.01-5PPM/USF370-10.0M-T-5PPM-ND/2139005 10 M ohm, 0.01%, 5 ppm/deg C. Then put it in a box. It's not good enough to perform a calibration, but not so far off. The 90-day specification for 10 M ohm of the data logger is +/- 2.1 k ohm, and the 1-year specification is +/- 4.1 k ohm. For 100 M ohm, both the 90-day and 1-year specifications are +/- 910 k ohm. I can't find any close tolerance 100 M ohm resistors around. Vishey makes some 0.5%, but I can't find anyone that stocks a small quantity. Digikey carries them, but the minimum order quantity is 100 pieces, which is totally out of the question. There is a guy from Ukraine selling what are supposedly close tolerance resistors, but I have no idea what they are actually like. -- Dr David Kirkby Ph.D C.Eng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD, Essex, CM3 6DT, United Kingdom. Registered in England and Wales as company number 08914892 https://www.kirkbymicrowave.co.uk/ Tel 01621-680100 / +44 1621-680100 _______________________________________________ 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. _______________________________________________ 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.
