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Keithley 6221 User Manual

Keithley 6221
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5-34 Delta, Pulse Delta, and Differential Conductance Model 6220/6221 Reference Manual
Return to Section 5 topics
The affects of heating can be eliminated by not performing the measurement at
point C (low pulse). For this 2-point measurement technique, Pulse Delta is calcu-
lated as follows:
Measurement units
The fundamental Pulse Delta measurement explained above is in volts. The read-
ing can instead be converted into Ohms (W), Siemens (S), or Power (W). Details
on selecting “Measurement units” are provided on page 5-16.
With Ohms or Siemens measurement units selected, the reading is calculated as
follows:
W = V/I
S = I/V
The calculation for power depends on the power reading type that is presently
selected (Peak or Average) and is discussed as follows.
Peak power and average power
With Power units selected, a Pulse Delta reading can be expressed (and dis-
played) as a Peak power reading or an Average power reading. Peak power is the
default setting.
Figure 5-9 shows how Pulse Delta voltage is calculated. Peak power is calculated
using the basic power equation (W = IV), where I is the high pulse current (I-High)
and V is the calculated Pulse Delta voltage.
The average power over the entire Pulse Delta cycle can calculated by factoring in
the duty cycle. Duty cycle is the percentage of time that the pulse is high during
the Pulse Delta cycle. For example, assume the period of the Pulse Delta cycle is
1ms. If the pulse is high for 0.25ms, then duty cycle is 25%.
Mathematically, duty cycle is expressed as follows:
Duty Cycle (in %) = Pulse Width / Pulse Interval x 100
Where: Pulse Width = Time that the pulse is high.
Pulse Interval = Time period of the Pulse Delta cycle.
PulseDelta
2B 2A
2
---------------------
⎝⎠
⎛⎞
1()
0
=
2 10.01()20.01()
2
-------------------------------------------------=
20mV
2
----------------=
10mV=
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - TestEquipmentDepot.com

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Keithley 6221 Specifications

General IconGeneral
InterfaceGPIB, RS-232
Communication InterfaceGPIB, RS-232
Current Sourcing Accuracy±(0.03% of output + 20 pA)
Current Sinking Accuracy±(0.03% of output + 20 pA)
Output Resolution100 fA
Output Accuracy±(0.03% of output + 20 pA)
Power Requirements100 V to 240 V AC, 50/60 Hz

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