Section 4: Theory of operation
2606B System SourceMeter® Instrument Reference Manual
4-18
2606B-901-01 Rev. B / May 2018
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 out to allow a stable measurement. By default (when power is turned on or
after a
smu
X
.reset()
command), delays are enforced to account for approximately 6
τ
or 6 time
constants of a given range (to reach 0.1 percent of the final value, assuming 2.3
τ
per decade). The
table below lists the current ranges and associated default delays.
Current measure settling time
1, 2
Time required to reach 0.1% of final value after source level command is
processed on a fixed range.
Values below for V
out
= 2 V unless otherwise noted
Current range
Settling time
1 A to 3 A
<120
µ
s (typical) (R
LOAD
>6
Ω)
100 mA to 10 mA
<80
µ
s (typical)
1 mA
<100
µ
s (typical)
100
µ
A
<150
µ
s (typical)
10
µ
A
<500
µ
s (typical)
1
µ
A
<2.5 ms (typical)
100 nA
<15 ms (typical)
1
Delay factor set to 1. Compliance equal to 100 mA.
2
Time for measurement to settle after a V
step
.
Delays are off by default for the 2606B but can be enabled.
You can manipulate the default delays to produce faster response 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 accounts for settling to 0.01 percent of the final value.
The following code provides measure delay examples for controlling settling time delay of SMU
Channel A:
-- To turn off measure delay (default setting is smua.DELAY_AUTO).
smua.measure.delay = 0
-- set measure delay for all ranges to Y (in seconds).
smua.measure.delay = Y
-- To adjust the delay factor.
smua.measure.delayfactor = 1.0
The delay factor is used to multiply the default delays. Setting this value above 1.0 increases the
delays; a value below 1.0 decreases the delay. Setting this value to 0.0 essentially turns off
measurement delays. This attribute is only used when
smu
X
.measure.delay
is set to
smu
X
.DELAY_AUTO
.