12
Logarithmic scale «Logarithm»
The screen in logarithmic scale:
This scale is used for the fast-access retrieval of the heterogeneity. The total viewing range is
100 dB. The top screen part is 0 dB, the bottom screen part –100 dB. The [AMPLIFICATION]
key do not have an in
fl
uence on trace displaying. There is the signal level
UdB
in dB near the
cursor, relatively the measuring pulse level
0
U
:
0
20 lg
U
UdB
U
=
×
,
The echo – signal level
U
is taken an absolute value, as far as the echo-signal can be positive
or negative. The positive values are displayed green and the negative values are yellow. On
rather long cables the negative values are seldom, and such image display feature is not falsify
a usual situation. Though, on the small pieces the picture may cause unusual. Switch on the
linear scale.
To make a logarithmic scale more usual there are realized an additional viewing mode –
«
+/-log
».
Logarithmic scale «± Logarithm »
These logarithmic scale is taken into account a signal character (+ or -): the positive signal
levels are displayed in the top part of the screen, the negative signal levels are displayed in the
bottom part of the screen ( from the top part: 0 dB of the positive signal, 60 dB, -60 dB, 0 dB
of negative signal).
You can select the suitable viewing mode by pressing the keys. Logarithmic scales it is
recommended to use with a rather long cables (more than 2-3 km), with a short cables it is
recommended to use a linear mode.
Installation for a distance measurement
If you does not choose the cable and work with default cable - it is necessary to establish VF (or
CC) an a range of a cable viewing. The distance between cursors will be calculated according
to VF in selected view range.
If the VF is unknown, the device will establish it on a Cable Type. For this purpose select e
necessary mark in Main Men \ Cable selection \ Cable Type.