User Manual

2400 Series SourceMeter
®
User’s Manual Pulse Mode Operation (Model 2430 only) 5-9
Jitter for pulse off-time can be as high as 1msec, depending on the integration
rate, auto zero, and on-time. In general, the higher the off-time, the higher the jit-
ter.
Pulse energy limitations (10A range)
Energy for pulses are provided by an internal bank of capacitors. Each pulse con-
sumes energy from the capacitors. After a pulse is generated, the capacitors
begin to recharge. The next pulse will occur at the configured time as long as the
capacitors have had enough time to recharge. If the capacitors are not charged
enough to provide the pulse, the instrument will wait until the necessary charge
energy is available.
Charge energy consumption by a pulse depends on the pulse current and pulse
width, and is expressed as follows:
Q = I × t
Where: Q is the charge energy consumed by the pulse
I is the pulse current
t is the output on-time (pulse width)
From the above equation, high current and/or long output on-time results in high
energy consumption, and therefore, longer charge time for the capacitors.
On all but the 10A range (source or measure), charge energy consumption is low
enough to allow the capacitors to recharge before the next pulse is due. This fast
recharge process allows the configured pulse period to be consistent (jitter free).
On the 10A range (source or measure), the configured pulse period will be consis-
tent as long as the pulse duty cycle is 8% or less. Above 8%, the capacitors will
not be able to recharge sufficiently before the next pulse is due. As a result, the
pulse period becomes longer (due to additional charge time between pulses) and
more inconsistent (jitter).
To achieve a consistent pulse period on the 10A range, set a pulse off-time that
will provide a duty cycle that does not exceed 8%. For example, if the pulse width
is 2msec, the required off-time is calculated as follows:
Pulse Off-time= (Pulse Width / Duty Cycle) - Pulse Width
= (2msec / 8%) - 2msec
= 25msec - 2msec
= 23msec
If a consistent pulse period is not required for your test, the 10A range allows you
to output fast, high energy (>8% duty cycle) pulses. With the pulse delay set to
0sec, each subsequent pulse will output as soon as the capacitors become suffi-
ciently charged.