Tettex 2293 - 3 Theory; General Resistance Measuring Principle

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Theory
3 Theory
3.1 General Resistance Measuring Principle
Basically the instrument consists of 3 programmable power supplies, which can operate in
constant current or constant voltage mode. Further, these power supplies operate in two
quadrants. This means that a power supply can act as an active load, which is used to quickly
discharge the current from high inductive DUT.
To determine the resistance of the DUT, the device uses 2 voltage and 2 current measuring units.
This way the unit can measure 2 different resistances with individual currents at the same time.
The resistance is calculated according to the principle described in the figure below:
Instrument
R
1
L
M
DUT
+
-
U
I
N1 : N2
ideal
N1 : N2
ideal
R
2
The resistance displayed on the device is calculated as follows:
dt
dI
L
I
U
I
UU
I
U
R
M
RLMR



The reading is correct only after the current has stabilized (dI/dt = 0).