Hey rastro,
Yes you are correct, but since we strive for perfection let´s look at the manual page to understand better the situation (pag. 6-31 6-31 or Fig 6-9):
as you can see the the connections are
Analog PCB Cable from Analog PCB Triax Output Connector (fig 2-2 manual)
-------------- ------------------------ -------------------------------
Exterior Black Insulator Chassis Common (Outer Triax Shield)
Output Common -------> Silver Braided shield * --------> Output Common (Inner Triax Shield)
Insulation 1 (Clear)
Analog Common -------> Copper Braided Shield
Insulation 2 (Clear)
Output -------> Silver Center Conductor -------> Output HI (Center Triax Condutor)
The analog common is just the guard voltage there, so that the Copper Braided Shield is there just to protect the output conductor from any leakage.
When the unit is turned on the guard white JIO14 (4mm banana jack on the back) and that conductor are connected together with the relais K307.
My questions/observations are now:
1) Why stop the guard at the triax JIO13 and not connect that with the Inner Triax Shield? The output common could have been connected to the Outer Triax Shield. Probably safety reasons?
2) The damage I did exposes just the guard, so any leakage there is not critical. The PTFE is reasonable there for the max 100V you could have between guard and ground common.
3) Why Keithley left so much space between the end of the Silver Center Conductor and the end of the Copper Braided Shield? It is not better to protect with the guard as much as you can?
To repair my damage this is my current plan:
1) cut 7-8mm of the Silver Center Conductor
2) Use the PTFE pipe I found there (see fig 2 and 3 from my old post) to cover the damage
if my assumptions are correct I will also reduce the leakage current at the connector triax since there is less Silver Center Conductor exposed without guard (probably about .00001% improvement).
Home
Help
Search
Login
Register
