Measurement Settling Time Considerations - Keithley 2601B Reference Manual

Series 2600B System SourceMeter® Instrument Reference Manual

Measurement settling time considerations

Several outside factors can influence measurement settling times. Effects such as dielectric
absorption, cable leakages, and noise can all extend the times required to make stable
measurements. Be sure to use appropriate shielding, guarding, and aperture selections when making
low-current measurements.
Each current measurement range has a combination of a range resistor and a compensating
capacitor that must settle to allow a stable measurement. By default (when power is turned on or after
a smuX.reset() command), delays are enforced to account for approximately 6τ or 6 time
constants of a given range (to reach 0.1 percent of the final value, assuming 2.3τ per decade). The
table below lists the current ranges and associated default delays. In addition, a 1 Hz analog filter is
used by default on the 1 nA and 100 pA ranges.
Current measure settling time
Time required to reach 0.1 % of final value after source level command is
processed on a fixed range.
Values below for V
Current range
1.5 A to 1 A
100 mA to 10 mA
1 mA
100 µA
10 µA
1 µA
100 nA
10 nA
1
1 nA
3
100 pA
1. Delay factor set to 1. Compliance equal to 100 mA.
2. Time for measurement to settle after a Vstep.
3. With default analog filter setting <450 ms.
Delays are on by default for the Model 2634B/2635B/2636B. Delays are off by default for the Model
2601B/2602B/2604B/2611B/2612B/2614B but can be enabled.
You can manipulate both the analog filter and the default delays to produce faster response times.
Turn off the analog filter to yield faster settling times. Control the default delays by using the delay
factor multiplier. The default value for delay factor multiplier is 1.0, but adjusting it to other values
result in either a faster or slower response. For example, increasing the delay factor to 1.3 will
account for settling to 0.01 percent of the final value. The commands to manipulate the delay factor
and analog filter are shown below.
2600BS-901-01 Rev. B / May 2013
1, 2
= 2 V unless otherwise noted
out
Settling time
<120 µs (typical) (Rload >6 Ω)
<80 µs (typical)
<100 µs (typical)
<150 µs (typical)
<500 µs (typical)
<2.5 ms (typical)
<15 ms (typical)
<90 ms (typical)
<360 ms (typical)
<360 ms (typical)
Section 4: Theory of operation
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