====== Keithley 181 Digital Nanovoltmeter ====== {{ :wiki:keithley_181.jpeg?nolink&200|}} {{ :wiki:keithley_181_digital_nanovoltmeter_operator_manual.pdf |181 Operator's Manual}}\\ {{ :wiki:keithley_181_digital_nanovoltmeter_service_manual.pdf |181 Service Manual}} === Application Notes === {{ :wiki:keithley_lo_level_measurements_handbook_7ed.pdf |Keithley Low Level Measurements Handbook 7th. Edition}} === 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 {{ :wiki:amphenol_97_series_standard_cylindrical_connector.pdf |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.