Section 3: Setting up SMUs in Clarius
Model 4200A-SCS Source-Measure Unit (SMU) User's Manual
3-30
4200A-SMU-900-01 Rev. A December 2020
The following table summarizes the Delay Factor settings.
Speed Mode
Delay Factor
Fast
0.7
Normal
1.0
Quiet
1.3
Custom
0 to 100
When entering a custom Delay Factor setting, consider the following:
•
A Delay Factor of 1 allows for settling before the analog-to-digital (A/D) converter is triggered to
make a measurement.
•
Each doubling of the Delay Factor doubles the time allowed for settling.
•
A delay factor of 0 multiplies the default delay by zero, resulting in no delay.
If you set the Filter Factor and Delay Factor to
0
, the internal preprogrammed values are ignored.
In general, cables and matrices increase the settling time. You may need to experiment to find the
ideal time. However, for a good quality switch, such as the Keithley 7174A High Speed Low Leakage
Current Matrix, you should not need to increase the Delay Factor by more than two times.
Filter Factor
To reduce measurement noise, each 4200A-SCS applies filtering, which averages multiple readings
to make one measurement. The Filter Factor is fixed for Fast, Normal, and Quiet speeds. If you select
the Custom Speed mode, you can enter a Filter Factor of 0 to 100. The default Filter Factor settings
are listed in the following table.
Speed Mode
Filter Factor
Fast
0.2
Normal
1
Quiet
3
Custom
0 to 100
When entering a custom Filter Factor, consider the following:
•
A Filter Factor of 1 provides filtering that is appropriate for most applications.
•
Increase the Filter Factor to average multiple readings for reduced noise. As a general rule,
doubling the Filter Factor halves the measurement noise.
•
Measurement time is increased by the square of the Filter Factor.
•
A Filter Factor of 0 nullifies the internal filtering.
When the Filter Factor and Delay Factor are set to 0, the preprogrammed values are ignored.
