Re: [volt-nuts] Vibrating reed electrometers

Another thing I noticed in these instruments - the highest R value used is E12, even though decades higher would have been appropriate in certain ranges. It shows that was about the practical limit for somewhat decent precision and cost. Filling in the desired higher ranges had to be done by

Re: [volt-nuts] Vibrating reed electrometers

Yup - Keithley 640 - that must be the one. This stirred my memory somewhat, and I just located info on the model 642 also, which was apparently newer. The 642 went to (or back to) ultra-low bias MOSFETs, while keeping sapphire insulation and a separate input head. The MOSFETs need all kinds of

Re: [volt-nuts] Vibrating reed electrometers

The Keithley model 640 was a vibrating capacitor electrometer. It was available in the 1970's. Bruce > > On 04 March 2018 at 06:34 george wrote: > > Hi all > > To the best of my memory Keithley never made vibrating reed > electrometers, the only one that I

[volt-nuts] Vibrating reed electrometers

Hi all To the best of my memory Keithley never made vibrating reed electrometers, the only one that I am aware of is the Varian Cary 401 which did use Sapphire insulators. I was the European product line specialist for Varian Cary in the late 1960/1970 era and was involved with the 401.