Keithley 2182, Руководство пользователя, Страница: 327 / 339

Delta, Pulse Delta, and Differential Conductance I-11
Measurement units
The fundamental Pulse Delta measurement explained on the previous page is in volts. The
reading can instead be converted into an Ohms (W), Siemens (S), or Power (W) reading
by the Model 622x.
With Power (W) units selected, a Pulse Delta reading can be expressed (and displayed) as
a Peak power reading or an Average power reading:
W (peak power) = I x V
W (Average power) = I x V x Duty Cycle
Pulse Delta outputs
Pulse Delta output is made up of one or more Pulse Delta cycles. Each cycle is made up of
three output pulses (low, high, and low). The time period for a cycle is adjustable and is
the same for all cycles. The output pulses have an adjustable pulse width, which is the
same for all pulses.
There are two basic Pulse Delta output types: Fixed output and Sweep output. For Fixed
output, all high and low pulses are fixed for all Pulse Delta cycles in the test. For Sweep
output, the sweep (SWP) function of the Model 6221 is used to output a staircased, loga-
rithmic or user-specified (custom) pulse sweep.
Fixed output
Figure I-5
shows one Pulse Delta cycle for a Fixed output. As shown, the Model 6221 out-
puts a low pulse, a high pulse and then another low pulse during every Pulse Delta cycle.
The pulse width is adjustable and is the same for all high and low pulses. The cycle inter-
val is also adjustable and is based on the set number of power line cycles. The Pulse Delta
interval shown in
Figure I-5 is set for 5 PLC (power line cycles), which is the default set-
ting. After the set interval expires, the next Pulse Delta cycle starts (if pulse count is >1).
Pulses are synchronized to the frequency of the power line voltage. When Pulse Delta is
started, the three pulses (low, high, and low) are generated on the positive-going edges of
the first three power line cycles. For the remaining power line cycles in the interval, the
output remains at the I-Low level.
Sweep output
The sweep feature of the Model 6221 can be used to output a series of pulses that allow
the use of different levels for the high pulses. Each high pulse returns to the programmed
low pulse level. The low level is the same for all pulses.
Like the Fixed output shown in Figure I-5 , a Sweep output is synchronized to the fre-
quency of the power line voltage, and the pulse width is adjustable and is the same for all
pulses.