2-14
IM AQ6376-01EN
Measurement Sensitivity and Vertical Axis Effective Range
When the measurement sensitivity is set to NORMAL HOLD, the internal amplifier has
a fixed gain. Five different gains are set automatically according to the reference (REF)
level setting. However, the effective range of measurement data is limited to the following
range, using the reference (REF) level (dBm) as a reference.
REF-20 dBm < (effective range) < REF+10 dBm
If the level scale is set to 10 dB/DIV, the display would exceed the effective range, so the
areas at 10 dB from the screen stop and 20 dB from the bottom are inaccurate.
When measurement sensitivity is set to NORMAL HOLD, we recommend setting the
level scale to 5 dB/DIV or less.
Under the measurement sensitivity settings NORMAL AUTO, MID, and HIGH 1/CHOP–
HIGH 3/CHOP, an automatic gain is used, permitting measurements over a wide level
range through a single sweep. Select the appropriate sensitivity level based on the light
reception level required for the particular measurement application.
Stray Light from the Monochromator
The instrument has a newly designed, high-performance monochromator. Depending
on the measurement conditions, stray light at a level 30 to 50 dB below the original
spectrum, as well as other stray light specific to the monochromator may occur in
wavelength areas about 300 nm from the peak wavelength. If this stray light is likely to
have a severe impact on measurements, the sensitivity can be set to HIGH 1/CHOP–
HIGH 3/CHOP in order to reduce the effects of the stray light.
Waveform with CHOP MODE invalid
Waveform with CHOP MODE valid
CHOP MODE Function List
CHOP
MODE
Function
Merit
Defect
Invalid
Measurement according to the
stray light.
Stray light suppression ratio:
40 dB or more
Measurement time is rapid
even for high sensitivity
measurements.
Since the stray light is also
measured, the low level
component is not accurate
if the light source is of high
power.
Valid
High dynamic measurement
using internal modulation.
Stray light suppression ratio:
60 dB or more
Measurement can be taken
with stray light removed.
Long-duration, high
sensitivity measurements
possible since offset does
not change.
Measurement time is long.
2.4 Important Points During Measurement