YOKOGAWA EML500 Series, User Manual, Page: 49 / 85

6-6
IM80B80T10E 21th Edition : Jul.1,2007-00
< 6.INSTALLATION >
6.4 Adjustments
(1) Zero Adjustment (Maintenance Mode)
A zero adjustment corrects a zero-point drift which may occur in a circuit other than the one in the
sensor. To make a zero adjustment, there mast be no water flowing in the direction to be detected.
Therefore, make the adjustment :
� with the sensor placed in a bucket of water, or
� with the ship at anchor and no water flowing around the sensor.
Furthermore,
� Lightly polish the electrodes in the sensor with the water-resistant sandpaper (at last #600) damp -
ened in water.
� Place the sensor in a bucket of water. Hold the sensor so that its electrodes are in the middle of
the bucket: do not let the electrodes come into contact with the bottom of the bucket.
The adjustment procedure is shown in the figure below.
This is the initial display (

-5-1 ) of the maintenance
mode. Press the
F 1
key at

-5-1 to select
zero-adjustment. The display then changes to that
marked a .
The values high-lighted in reverse video here are
the zero-adjustment data that were the latest set.
To make a new zero adjustment, press the
F 1
key ('GO'). The display changes to that marked b ,
and then further changes to that marked c after
approximately 20 seconds. On this display, the
new zero-adjustment data are displayed.
Press the
ENT
key to enter the data.
Press the
PREV
key when the data are not en-
tered.
At

-5-1 , press the
F 2
key (NXT) to advance
to sensitivity adjustment (

-5-2 ).
(Refer to page 6-7 for details on sensitivity adjust-
ment.)
The sensor must be kept
away from the bottom of
the bucket
ø 500
At least 100 mm
F 1 F 2 DISPL PREV MODE
F 1 F 2 DISPL PREV MODE
MAINT
MAINT
F 1 F 2 DISPL PREV MODE
MAINT
F 1 F 2 DISPL PREV MODE
MAINT
a.

-5-1

-5-2

-5-11
b.
c.
Previously-set value
Display of measured
value
Start of
measurement
F 1 F 2 DISPL PREV MODE
F 1 F 2 DISPL PREV MODE
MAINT
MAINT
F 1 F 2 DISPL PREV MODE
MAINT
F 1 F 2 DISPL PREV MODE
MAINT
a.

-5-1

-5-2

-5-11
b.
c.
Previously-set value
Display of measured
value
Start of
measurement