Keithley 417 pico ammeter teardown

[uoficowboy]

I recently acquired a Keithley 417 pico ammeter. I think you all will appreciate it. It is a very cool piece of old school equipment. I imagine it was very costly many years ago. It supports full scale ranges from 30ua to 100fa in 18 different ranges. At any range, a full scale input will have a 1mV drop. Yowza.

The top sets of knobs set the full scale range that it is measuring. The bottom set of knobs sets a current that is being subtracted or added from the input current. So this way, you can have a 1.0-1.01ua current that you are interested in, then you can subtract 1ua, and then put the device on a 10na full scale range. Pretty cool.

Full size pics here: http://imgur.com/a/SvEO0 - but I've added captions to quarter size pics below:

How it looks with clothes on:


The top comes off after you rotate two plastic latches 90 degrees. This exposes the power supply, some rotary switches, and a 10 turn pot.


This is the largest 10 turn pot I have ever seen. It makes a very satisfying sound when you turn it and seems to be in top notch condition.

The input head comes off after you remove a single thumbscrew from the back of the device. Very easy.

You can then remove the case from the input head with a single screw.

Inside of the input head you can see a metal box with 5 leads coming out of it. That is a vacuum tube that is part of the amplifier for this device.

Further, there are more rotary switches. The passives on these switches are wonderful - some of the resistors seem to be wire wound and then glass encapsulated? I've never seen anything like it.


I also really like how they seem to have made adjustable capacitors by putting metal tubes over some of these glass resistors. and sliding them around. Very fun.

Here is a close up of the beefiest looking rotary switch. Looks like all gold. Beautiful.

Anyways - that's all for now. The device seems to be 100% operational which is pretty impressive considering its age. I will probably part with it on Ebay eventually since it's a bit large - but it sure is sexy.

[daqq]

Thanks for the teardown! Really nice to see this kind of stuff!