User manual

I-8 Delta, Pulse Delta, and Differential Conductance
Delta calculation example
Assume you wish to measure the voltage across a 1
DUT using a constant +10mA cur-
rent source and a voltmeter. Ideally, the measured voltage would be 10mV (V = I x R).
However, due to a 10µV thermal EMF in the test leads, the voltmeter actually reads
10.01mV (0.1% error due to EMF).
The error contributed by EMF can be eliminate by using Delta. Assume the square wave
output of the Model 622x is set to 10mA (high) and -10mA (low) and the following Model
2182/2182A measurement conversions (A/Ds) are made for the first Delta cycle.
A/D A = 10.01mV
A/D B = -9.99mV
A/D C = 10.01mV
The first Delta reading is calculated as follows:
The 10mV Delta reading effectively cancelled the 10µV EMF to provide a more accurate
measurement.
Measurement units
The fundamental measurement for Delta is voltage (Volts; V). However, the voltage read-
ing can converted into a conductance (Siemens; S), resistance (Ohms; W), or power
(Watts; W) reading by the Model 622x.
Delta
A 2B C+
4
---------------------------


1()
0
=
10.01mV 2 9.99mV() 10.01
˙
mV+
4
---------------------------------------------------------------------------------------


1=
40mV
4
--------------


=
10mV=