Keithley 485
The Keithley 485 Picoamperemeter is a dedicated picoamperemeter from the mid-1980s, from the same generation and model series as the better-known Keithley 197 "Microvolt DMM".
The 485 operates as a feedback (transimpedance) amperemeter (i.e. the input burden is constantly low at less than 0.2 mV), has a resolution of 4½ digits (19999), some rudimentary built-in logging capabilities, as well as an optional GPIB interface.
This instrument measures only (low) currents, in seven decadic ranges from 2 nA to 2 mA full scale. In the 2 nA range, the least significant digit resolves 100 fA (0.1 pA).
Key Specifications
| Current | 7 decade ranges, 2 nA to 2 mA full scale |
|---|---|
| Display | 4½ digits, LCD |
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See also
Internals
The (optional) GPIB interface communicates with the base instrument over an opto-isolated serial port. It uses a separate 6805 CPU.
Pictures
Components
Some Parts Used in the Keithley 485
| Part | Part Number(s) | Class | Description | Used in |
|---|---|---|---|---|
| Motorola 6800 | 156-0426-00 • 156-2413-00 • 156-5472-01 | Monolithic integrated circuit | 8-bit microprocessor | 021-0206-00 • 021-0374-00 • 067-0902-00 • 067-1137-99 • 222 • 222A • 222PS • 2424L • 2445 • 2465 • 2467 • 4051 • 7250 • 7912 • 7912AD • 7A16P • 7A29P • 7B81P • 7B90P • 833 • 834 • 835 • 836 • CG5001 • CG551AP • CG5010 • CG5011 • DF1 • DF2 • DM5010 • FG5010 • MI5010 • SI5010 • PS5004 • PS5010 • SG5010 • Keithley 181 • Keithley 182 • Keithley 175 • Keithley 175A • Keithley 191 • Keithley 192 • Keithley 195 • Keithley 195A • Keithley 197 • Keithley 220 • Keithley 224 • Keithley 230 • Keithley 263 • Keithley 485 • Keithley 580 • Keithley 617 |
| Motorola 6820 | 156-0427-00 | Monolithic integrated circuit | "Peripheral Interface Adapter (PIA)" | 021-0206-00 • 7A16P • 7B81P • 7B90P • Keithley 175A • Keithley 197 • Keithley 485 • Keithley 580 |
| NEC μPD7225 | Monolithic integrated circuit | LCD driver | Keithley 175A • Keithley 197 • Keithley 485 • Keithley 580 |