Agilent Technologies 4339B, Operation Manual

Page: 116 / 287

Theory of Operation 4339B
Theory of Operation
This section provides the 4339B's theory of operation.
In \Overall Measurement Theory" and \Overall Block Diagram ", we will discuss the
measurement theory with the ungrounded DUT measurement conguration. These descriptions
can also be applied to the measurement of a grounded DUT , considering the test signal ow
shown in Figure 3-10 (b).
Overall Measurement Theory
The 4339B measures the Device Under T est (DUT) resistance in the following manner .
Figure 3-8. Simplied Model of Impedance Measurement
Figure 3-8 shows a simplied model of the 4339B measuring a DUT . In the Figure 3-8, the DUT
is connected in series with a test voltage source , V , and an ammeter , A. Rs is the 4339B 's source
resistance (R s = 1k ) and Ri is the input resistance (R i = 1k ).
In the resistance measurement mode (the measurement parameter is R), the 4339B displays
the \derived" DUT resistance , Rx. In other words , if the ammeter measures Ix when the
source voltage is V, the 4339B displays the DUT resistance Rx, calculated using the following
equation:
R x =
V
I x
0 (R s + R i)
In the current measurement mode (the measurement parameter is I), the 4339B measures
the actual current value , Ix, which ows through the DUT , and displays the value for the
measurement result. F or example , if R
x
is 100 k, and V is 1 V, the measurement result will be
9.8 A (
1 V
100 k +2k
). If you measure a DUT whose resistance value is lower , the 4339B 's source
resistance , Rs, and input resistance , Ri, aect the measurement current value , Ix, more .
3-26 Function Reference