2600S-901-01 Rev. C / January 2008 Return to Section Topics 8-23
Series 2600 System SourceMeter® Instruments Reference Manual Section 8: Source-Measure Concepts
Pulse duty cycle
Duty cycle is the percentage of time during the pulse period that the output is on. It is calculated as
follows:
Duty cycle = Pulse width / (Pulse width + Off time)
For example, if the pulse width is 10msec and the off time is 90msec, the duty cycle is calculated
as follows:
Duty cycle = 10msec / (10msec + 90msec)
= 10msec / 100msec
= 0.10
= 10%
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 7
Ï„ or 7 time constants of a given
range (to reach 0.1% of the final value, assuming 2.3
Ï„ per decade). The table below lists the
current ranges and associated default delays. In addition, a 1Hz analog filter is used by default on
the 1nA and 100pA ranges.
Table 8-4
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 Vout = 2V unless noted
Current range Settling time
1.5A to 1A <120μs (typical)(Rload>6Ω)
100mA to 10mA <80μs (typical)
1mA <100μs (typical)
100μA <150μs (typical)
10μA <500μs (typical)
1μA <2.5ms (typical)
100nA <15ms (typical)
10nA <90ms (typical)
1nA
1
<360ms (typical)
100pA
3
<360ms (typical)
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 < 450ms.
Both the analog filter and the default delays can be manipulated for faster response times. The
analog filter may be turned off to yield faster settling times. The default delays may also be
controlled by using the delay factor multiplier. The default value for delay factor multiplier is 1.0,
but adjusting to other values will result in either a faster or slower response. For example,
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