MW1008P, user manual
25
OPEN / SHORT CALIBRATION
This function allows to compensate for the parasitics elements of the test cable in order to
take them into account during value display. The model used is the one shown on the figure
below :
The instrument finds out the values of the serial elements Rss and Lss during a short circuit
measurement. The values of Gpp and Cpp being measured during an open circuit
measurement. The MW1008P takes these elements into account by applying the correction
given on the schematics (a) above. The calibration should be done at each time one proceed to
measurements in the measurement range boundaries, meaning for weak impedance values
(high capacitors values of low inductor values) and for high impedances (small capacitors
values and strong inductors values). The open/short calibration is besides mandatory to
measure with a small error the losses in a components, like the serial equivalent resistance of
a capacitor.
Some care has to be taken during open/short calibration.
The position of the cables must not
change between calibration procedure and component measure.
Any change of spacing or
any other change in cables position could change the parasitic elements that could bring an
error in the measurement. During the open/short calibration, one can use a small wire piece on
which could be connected the 4 mini-pincers (MW10) or the 2 Kelvin clamps (MW-KELV).
For the measurement of very low impedances, one should place the pincers at right angle (90
°) to minimise coupling between wires as shown on figure below. The same arrangement
should be used during measurement itself.
