Keithley 6220 Reference Manual page 173

Model 6220/6221 Reference Manual
Differential Conductance calculations
dV calculations
While the dV calculations for the first six dV readings are shown in
the following formula can be used to calculate any dV reading in the test:
(
------------------
------------------------------------------- -
dV
=
Where:
Example – Calculate the 21st dV reading:
X, Y and Z are the three A/D measurements for the 21st dV reading.
n = Reading Number – 1
= 21 – 1
= 20
Therefore;
(
------------------
------------------------------------------- -
dV =
= ------------------------------------------- -
The (-1)
calculated dV reading. This makes all calculated dV readings in the test the same
polarity.
Simplified dV calculation
The above dV calculation can be simplified as follows:
dV
=
dV =
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) ( )
X Y – Z Y –
+ ----------------- -
2 2
• – ( )
1
2
X, Y and Z are the three A/D measurements for a dV reading.
n = Reading Number – 1
) ( )
X Y – Z Y –
+ ----------------- -
2 2
• – ( )
1
2
( ) ( )
X Y – Z Y –
------------------ + ----------------- -
2 2
2
n
term in the dV calculation is used for polarity reversal of every other
X Y Z Y
– + –
--------------------------------- -
2
n
• – ( )
--------------------------------- - 1
2
X 2Y Z
– + n
• – ( )
-------------------------- -
1
4
Return to
Delta, Pulse Delta, and Differential Conductance 5-53
n
20
Section 5 topics
Figure 5-14,