Pulse Width - Keithley SourceMeter 2400 User Manual

5-4 Pulse Mode Operation (Model 2430 only)

Pulse width

The pulse width can be set from 0.15msec to 5.00msec. However, depending on how the
SourceMeter is configured, the pulse width setting may not be achievable. For example, if
it takes 1.667msec to perform the signal measurement, the minimum pulse width that can
be achieved is 1.75msec (1.667msec signal measurement plus 80µsec overhead). There-
fore, if the pulse width setting is shorter than what is achievable, the setting is ignored.
The maximum pulse width for the 10A range (source or measure) is 2.5msec. If the setting
is >2.5msec, the SourceMeter will limit the pulse width to 2.5msec.
Signal measurement
A pulse reading consists of three measurement conversions. The signal (pulse) is mea-
sured, a precise internal reference is measured, and finally, zero (common) is measured.
The reading is calculated from these measurements.
As shown in Figure
width, while the reference and zero measurements (Meas Ref & Zero) are components of
the off-time. The measurement process is split up this way to allow the shortest possible
pulse width. The time to perform the signal measurement depends on the speed setting
(NPLC) of the SourceMeter and the power line frequency:
Meas Sig = NPLC / Line Frequency
Where: Meas Sig is the time it takes to measure the signal.
NPLC is the present speed setting (0.004 to 0.100 PLC).
Line Frequency is the frequency of the power line (50 or 60 Hz).
NOTE For front panel operation, the menu to set speed is displayed by pressing the
SPEED key. For remote operation, speed is set using an :NPLCycles command.
See Section
Overhead time
As shown in Figure
measurement process. The 80µsec is the minimum overhead times that can be achieved. If
the SourceMeter is configured to perform additional operations (e.g., math calculations,
relative, store, sweep), this time will be higher.
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2400 Series SourceMeter
5-2, the signal measurement (Meas Sig) is a component of the pulse
7, "Speed," for details.
5-2, there is some pulse width overhead time that is inherent to the
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User's Manual