Haefely 2830, User Manual, Page: 28 / 124

20 Device Functions
6 Device Functions
6.1 System Overview
To be able to execute correct and reproducible measurements it is essential to
understand how the measuring system works.
6.1.1 C & tan δ
The 2830 C & tan

measuring system is based on the double vector-meter method which relies
upon the measurement of the current I
N
through the known reference capacitor C
N
and the
measurement of the current I
X
through the unknown test object C
X
.
Both branches are energized by the HV AC power source (U
Test
) which is built in the 2831. Both
currents are measured by the adjustable high accurate shunts R
X
and R
N
and then digitised. By
using a sample number for each digitised value and a known sample rate a timestamp is
calculated. With this technology not only the values but also the time information (phase
displacement) between I
N
and I
X
can be measured very fast and highly accurate.
The digitised data streams are fed into the built-in PC of the 2830 and over the known standard
capacitor built in the 2831. All other desired measuring values can now be determined online.