Megger IDAX 300, User Manual

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IDAX 300/322/350 ZP-AG03E AG033586EE
7 APPENDIX BMEASuREMENT TECHNIquE
7
A
ppendix B
Measurement technique
Short overview of measurement principle is given in
this chapter.
How impedance is
measured Gives basic principle of IDAX
operation
Modelling principles Description of the model
Sample modelling
Describes theoretical
models used for presenting
measurement results
7.1 How impedance is
measured
IDAX measures impedance. By measuring the
impedance at one point, i.e. at a specific frequency
and amplitude, parameters such as tan delta/power
factor, capacitance and resistance can be calculated.
The impedance of a sample is measured by applying a
voltage across the sample. This voltage will generate a
current through the sample. By accurately measuring
the voltage and the current, the impedance can be
calculated, see illustration below.
Fig. 7.1 Measurement of electrical impedance.
The impedance is calculated using Ohm’s law:
Z =u / I
where Z, u and I are complex entities.
The voltage (and the current) is generated by a
voltage source. There are currently two internal
voltage sources available in the IDAX system, which
can deliver a maximum peak output of 10 V
peak
and
200 V
peak
, respectively. The voltage is measured by
means of a voltmeter and the current is measured by
an ammeter or electrometer which acts as a current-
to-voltage converter.
The analogue signals (voltages) are then converted
to digital samples of the signals that are used in
subsequent calculations.