Keithley 6482, Reference Manual

Page: 63 / 350

4-2 Return to Section Topics 6482-901-01 Rev. A / August 2012
Section 4: Range, Digits, Speed, and Filters Model 6482 Dual-Channel Picoammeter / Voltage Source Reference Manual
Range and digits
This topic discusses available ranges, maximum readings, ranging limitations, manual and
autoranging, and display resolution.
Measurement range
The selected measurement range affects the accuracy of the measurements and the maximum
signal that can be measured.
Available ranges
Table 4-1 lists the available current measurement ranges, resolution values, and maximum
readings for each Model 6482 channel.
NOTE
The current measurement range can be set individually for each channel.
Maximum readings
As shown in Table 4-1 , the full scale input for each current measurement range is 105 percent of
the selected range. For example, ±21 mA is the full scale reading for the 20 mA range. Input levels
that exceed the maximum levels cause the
Oflo
message to be displayed.
Manual ranging
Press the MSR1 or MSR2 key, and then use the RANGE and keys to select a fixed channel
1 or channel 2 manual range.
NOTE
Use the lowest range possible without causing an overflow to ensure best accuracy and
resolution.
Autoranging
Press the MSR1 or MSR2 key, and then press the AUTO RANGE key to enable autoranging on
channel 1 or channel 2 respectively. The AUTO indicator turns on when autoranging is selected.
With autoranging selected, the instrument automatically chooses the best range to measure the
applied signal. In 2-channel, RATIO, or DELTA display modes, the AUTO indicator appears if
either channel is in autorange. Pressing the
AUTO RANGE key in the 2-channel display mode
toggles autorange ON or OFF on both channels.
NOTE
With the median filter enabled, autoranging can be very slow. See “Median filter,”
page Section 4-7 for details.
Table 4-1
Current measurement ranges
Model 6482
I-range Maximum
resolution Maximum
reading
2 nA
20 nA
200 nA
2 µA
20 µA
200 µA
2 mA
20 mA 1 fA
10 fA
100 fA
1 pA
10 pA
100 pA
1 nA
10 nA ±2.1 nA
±21 nA
±210 nA
±2.1
μ
A
±21
μ
A
±210
μ
A
±2.1 mA
±21 mA