YOKOGAWA 51011, User Manual

Page: 36 / 57

IM 51011-01EN
35
Setting the Ripple Ratio
The ripple ratio must be set prior to ripple measurements.
As long as the conditions remain the same (same type of
fluorescent lamp), you do not have to reset the ripple ratio.
Fluorescent lamps are unstable immediately after they are turned
on. Set the ripple ratio after at least 30 minutes elapses after
the lamps are turned on.
Select a location in the room where there is little ambient light and
also directly below the fluorescent lamps.
Never move the lux meter during this procedure.
1.
Face the light-detecting surface of the lux meter to
the fluorescent lamps to be measured, and then press
SET
and then
S-F
. The total illuminance will be measured.
After about 5 seconds, [-------] appears.
2.
When [L-OFF] appears, turn off the fluorescent lamps.
3.
Press
SET
. The ambient light will be measured.
After about 3 seconds, [-------] appears. When the ripple
ratio is set properly, the meter returns to normal illuminance
measurement.
If “Err” appears, the ripple ratio is not set.
If this occurs, press
SET
to return to normal illuminance
measurement, change the location, and try again.
An error will occur in the following circumstances.
• If the illuminance of ambient light is greater than or equal to
that of the fluorescent lamps: Err. 3
• If the AC component is extremely small or large compared to
the illuminance to be calculated: Err. 0
The set ripple ratio is retained even when the power is turned
off (the ratio is retained until it is changed).
Ripple Measurement
1.
Press
S-F
. [S-F] appears, and measurement starts.
To view the ripple ratio, hold down CALL .
2.
To return to normal measurement, press
S-F
. [S-F] disappears.