Hameg HM 8027 Manual De Usario página 15

General
A distortion factor meter is used to mea-
sure the distortion content of an otherwise
pure sine wave signal. The proportion of
distortion is displayed as a percentage of
the measured signal.
Distortions, in general, represent undesired
components of a signal being produced by
or passing through a non-linear system.
There are different kinds of distortion,
which are more or less pronounced
depending on the type of system used for
measurement set-up. Harmonic distortions
occurring e.g. in signal generators consist
of undesired frequencies which are inte-
ger multiples of the generated frequency.
These harmonics of different order vary in
phase and amplitude. They are detected as
effective values during distortion mea-
surement.
The most frequently measure used for des-
cribing nonlinear distortions is the distortion
factor. It specifies the share of harmonics
in the total signal. There are two different
sorts of distortion factors: The overall
distortion factor designated „d", and the
n-th order factor „dn" which is also called
partial distortion factor or distortion coef-
ficient. A distortion meter, such as the
HM8027 model, determines the overall
distortion factor (d) defined by the following
formula:
100% calibration
The signal to be investigated is to be applied
to the INPUT socket (9). Via this socket, the
HM8027 module accepts input voltages ran-
ging from 0.3V to 50V. Within this voltage
range, the instrument can be adjusted to
16
100% full deflection. Smaller voltages per-
mit no 100% adjustment, thereby leading
to inaccurate distortion factor readings;
higher voltages are also situated beyond the
adjustment range and can result in des-
truction of the HM8027 input stages. Within
the admissible voltage range, the signal is
adapted by use of two attenuators (11) and
the calibration knob (8).
The alignment mode is selected by pressing
the CALIBRATION pushbutton (7). When
the 100% calibration is completed, the fre-
quency alignment is then carried out. A new
100% calibration is only required when the
input signal amplitude has been changed.
Frequency alignment
During frequency alignment, the frequency
of the integrated filter is tuned to the input
signal frequency. First the FREQUENCY
RANGE pushbuttons (2) are pressed to
select the range of the input signal
frequency. The available frequency ranges
are subdivided as follows:
20Hz to 200Hz,
200Hz to 2kHz,
2kHz to 20kHz.
The continuous adjustment within the se-
lected range is performed by means of knob
(5). During this coarse adjustment, one of
the two LEDs indicates the direction of the
frequency deviation of the integrated filter
with respect to the input signal; i.e. when
the LED on the right lights up, the adjust-
ment knob must be turned counter clock-
wise, until the LED goes off, and vice versa.
When both LEDs are off, the alignment
procedure is completed. Fine adjustment
is carried out by the integrated automatic
alignment cicuitry with a capture range of
about 15%.
Selection of the distortion range
When the frequency alignment has been
accomplished, the desired measurement
range is selected by pressing the
DISTORTION pushbuttons (6). In case of
unknown magnitude of the distortion factor,
Änderungen vorbehalten / Subject to change without notice