Old 640 vibrating capacitor electrometer
Posted: August 4th, 2013, 2:11 pm
My apologies in advance for this long(ish) post and if this isn't the place for my inquires.
I used Keithley electrometers 45 years ago when I was an undergrad and graduate student (involving the measurement of photomultiplier tube currents) and became fascinated by the metrology of low current measurement. In the late 60's I expressed my interest to the company, making it clear that I wasn't looking for job; just being very curious and interested. To my surprise I was invited to Cleveland to visit the facilities and talk with some engineers. At the end of the visit that day I was treated to a (brief) meeting with Dr. Joseph Keithly, company founder.
The, after nearly 40 years of teaching lighting engineering, I retired from the University of Colorado and returned to my interest in Keithley electrometers as a hobby. I have since collected most of the instruments in this field that Keithley made (eBay, UsedLine and so on), beginning with the model 200 and 210 electrometer voltmeters that Dr. Keithley first offered. So far I have, in all, 23 Keithley electrometers. Many I have refurbished (replacing vacuum tubes, electrolytic capacitors that have gone bad, old connectors, readjusting/recalibrating and so on. Some are now quite rare, some surprisingly common. I have a beautiful version of the 642 -- gate current ~ 3x10-17a, very low noise. An amazing instrument and one of the best things Keithley ever offered.
I very recently finally acquired two contollers and a measurement head that comprised the Keithley 640 vibrating capacitor electrometer. The do not behave. I have worked carefully with the manual, doing the various voltage adjustments and circuit checks listed -- those are in order. I suspect something is wrong with the DC amplifier in the controllers, but am not sure. Finally my question: is there anyone at Keithley who recalls enough about this instrument to provide some guidance? If not, can anyone make a recommendation for someone who has?
It is my hope and plan to establish an website to showcase these interesting hallmarks or metrological progress.
Regards,
D.L.DiLaura
I used Keithley electrometers 45 years ago when I was an undergrad and graduate student (involving the measurement of photomultiplier tube currents) and became fascinated by the metrology of low current measurement. In the late 60's I expressed my interest to the company, making it clear that I wasn't looking for job; just being very curious and interested. To my surprise I was invited to Cleveland to visit the facilities and talk with some engineers. At the end of the visit that day I was treated to a (brief) meeting with Dr. Joseph Keithly, company founder.
The, after nearly 40 years of teaching lighting engineering, I retired from the University of Colorado and returned to my interest in Keithley electrometers as a hobby. I have since collected most of the instruments in this field that Keithley made (eBay, UsedLine and so on), beginning with the model 200 and 210 electrometer voltmeters that Dr. Keithley first offered. So far I have, in all, 23 Keithley electrometers. Many I have refurbished (replacing vacuum tubes, electrolytic capacitors that have gone bad, old connectors, readjusting/recalibrating and so on. Some are now quite rare, some surprisingly common. I have a beautiful version of the 642 -- gate current ~ 3x10-17a, very low noise. An amazing instrument and one of the best things Keithley ever offered.
I very recently finally acquired two contollers and a measurement head that comprised the Keithley 640 vibrating capacitor electrometer. The do not behave. I have worked carefully with the manual, doing the various voltage adjustments and circuit checks listed -- those are in order. I suspect something is wrong with the DC amplifier in the controllers, but am not sure. Finally my question: is there anyone at Keithley who recalls enough about this instrument to provide some guidance? If not, can anyone make a recommendation for someone who has?
It is my hope and plan to establish an website to showcase these interesting hallmarks or metrological progress.
Regards,
D.L.DiLaura