Furuno FCV-30 - Manual (Page 79)

3. CHANGING SETTINGS
3-11
3.8 Target Sphere Calibration Dialog Box
To accurately analyze fish distribution, it is necessary to calibrate target strength using a
calibration sphere. The calibration is done to jibe the target strength (TS) value displayed in
the fish histogram dialog box with the TS of the calibration sphere.
Follow the procedure below to perform the calibration.
1. Suspend a calibration sphere at least 3 m directly below the transducer.
2. Open the fish histogram dialog box.
3. While observing the echo sounder image, adjust the area marker (yellow rectangle) to
place the echo of the calibration sphere within the area marker. (See paragraph 1.12.1
for details.)
Set the marker at the right edge of the screen in order to measure with most recent data.
It is recommended to make the measuring area as small as possible to keep unwanted
echoes out of the measuring area, however the calibration can be performed with any
size measuring area.
4. Note the TS value in the fish histogram dialog box.
There is no problem if the TS value and the TS value of the calibration sphere do not
agree. Ideally, it is desirable if the distribution graph in the fish histogram window shows
only one bar for the calibration sphere, however the calibration can be executed
regardless of distribution.
5. Confirm that the echo from the calibration sphere appears in the area marker in
consecutive scans.
6. Click System on the menu bar.
7. Click Test/Initialization.