Keithley 181 Digital Nanovoltmeter
Application Notes
Accessories
Model 1506 Low Thermal EMF Input Cable
Keithley delivered Model 181 nanovoltmeter together with a low thermal EMF cable named “model 1506”. But for reasons I am not aware of, I have never seen a 181 nanovoltmeter being sold together with its model 1506 low thermal EMF cable. But I was lucky enough to score a 181 with half of a connector. From this partial model 1506 and using the service manual I inferred what it might have been:
Model 1506 Connector is a Amphenol 97 Series Standard Cylindrical Connector:
- Amphenol Shell: 97-3106A-16 (676 - Bright Nickel, or 689 - Electroless Nickel, idk)
Amphenol Insert: 97-20-23P (426 Gold over Silver Plating)- Insert is too big and pins have wrong diameter.- Amphenol Cable Clamp: 97-3057-1008 (676 or 689)
- Amphenol Rubber Bushing: 9779-513-8
Amphenol 97 series selection catalog
All parts can be purchased separately on Mouser. Unfortunately Digikey did not have any matching components.
The Model 1506 cable is a triaxial, teflon insulated cable most probably with bare, uncoated berillium-copper strands. The cable was soldered to the pins of the connector using low EMF solder containing cadmium. Either berillium-copper or bare copper alligator clips were soldered to the other end of the cable. I'm still unaware of the exact triaxial cable that was used or a source for low thermal EMF solder to recreate the cable.