Keithley 6485 User Manual

Model 6485 Picoammeter Instruction Manual Applications Guide I-15
Figure I-12
Down-range voltage transients
Steps to minimize impact of range change transients
When changing between the following range pairs (up or down), no input transients occur:
2nA and 20nA; 200nA and 2µA; 20µA and 200µA; 2mA and 20mA. This is not true when
auto-ranging upwards across these boundaries.
Run test with a fixed range.
If possible, run the test within a fixed range. Choose the higher range from any of the
range pairs listed above. Alternatively, the autorange upper limit
(:RANGe:AUTO:ULIMit, see “Voltages greater than 220V,” page 2-6 or “Autorange lim-
its,” page 4-3 can be set so that the internal limiting resistor (R
F
) cannot be reduced to the
lower values. Choose the appropriate range to accommodate the maximum current
expected during normal measurements.
Down-range by starting at highest current necessary
Make use of down-ranging by starting at the highest current necessary and reducing down
to zero, the range change transients can be reduced significantly compared to up-ranging
transients.

Keithley 6485 Specifications

General

Model	Keithley 6485
Category	Picoammeter
Input Impedance	>10^14 Ohms
Voltage Burden	<200µV
Accuracy	0.4% of reading
Voltage Source Range	Not Applicable
Voltage Source Resolution	Not Applicable
Voltage Source Accuracy	Not Applicable
Interface	IEEE-488
Power Requirements	100V to 240V AC, 50/60Hz
Dimensions	89 mm high x 214 mm wide x 369 mm deep (3.5 in x 8.4 in x 14.5 in)