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4
either positive or negative DC voltage to the DUT. A voltage drop
on the DUT is measured by DAu.
The voltage drop on resistor Rj
measured by DAj is proportional to the current flowing through
the measured component. After digitizing the ADC signals the
impedance is calculated according to the formula DUT
impedance Z =Rj* Vau/Vaj.
Initial values of Impedance (offsets) obtained during calibration
with Open and Short probes are stored in the non-volatile
memory of the device and are considered in the calculation of
the impedance of the measured component thus eliminating the
offsets due to the device internal parasitics.
The measured component can be represented as one of the
following equivalent circuits:
(1) and (2): AC measurement series circuits, (3) and (4): AC
parallel circuits, (5,6,7) DC measurement of diodes, resistance
and capacitance.
Impedance in series circuits is Z = Rs + iXs and in parallel circuits
is Z = 1/(1/Rp + 1/iXp) where Xs (Xp) < 0 if the reactance is
Capacitive and at Xs (Xp) > 0 the reactance is Inductive.
4.1 Calculation of Parameters:
Capacitance C
= 1/(2π
f
|Xs|) where
f
is the test frequency.
Inductance L = Xs/(2π
f
). Q = |Xs|/Rs. D = 1/Q. |Z| =
In automatic mode the device automatically selects the optimum
frequency and the equivalent circuit for measurements. Users
can also manually select measurement mode and frequency of
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