4-20
Return to
2600AS-901-01 Rev. B / September 2008
Section 4: Source-Measure Concepts
Series 2600A System SourceMeter® Instruments Reference Manual
Figure 4-13
Comparison of unguarded and guarded measurements
Settling time considerations
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. Care should be taken 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 (on power up or after
smuX.reset()
), delays are enforced to account for approximately 6
τ
or 6 time constants of a
given range (to reach 0.1% of the final value, assuming 2.3
τ
per decade). The table below lists the
Insulator
I
D
DUT
Metal Mounting Plate
I
L
R
L1
R
L2
Insulator
I
M
= I
D
+ I
L
I
M
= Measured current
I
D
= DUT current
I
L
= Leakage current
IN/OUT
HI
I-Meter
IN/OUT
LO
V-Source
A. Unguarded
I
D
DUT
Metal Mounting Plate
R
L1
Insulator
I
M
= I
D
IN/OUT
HI
I-Meter
IN/OUT
LO
V-Source
x1
GUARD
0V
SourceMeter
SourceMeter
B. Guarded
Connect to earth safety ground
using #18 AWG wire or larger.
Cable Shield
Safety Shield
