Newport 1830-C - 4.5.3 Relative Measurements

18
To make dBm measurements (relative to 1 mW optical power) with back-
ground correction, proceed as follows:
a. Select the dBm measurement mode, auto-range, and a wavelength.
b. Block the light to be measured.
c. Initiate background correction by pressing the ZERO key. Display
should read approximately zero, but will fluctuate depending upon the
variations in the amount of light reaching the detector and the detector
dark current fluctuations.
d. Illuminate the detector with the optical signal to be measured.
e. Take the reading from the display.
4.5.3 Relative Measurements
The relative mode REL is selected by pressing the UNITS key until the REL
annunciator turns on. The referenced power is selected at any time by press-
ing the STOREF key. The following equation illustrates this relationship:
REL reading = Net Applied Power/ Net
Referenced Power(=STOREF)
= (( I - I
z
)/R)/((I
STOREF
- I
Z
)/R)
where
I = detector input current
I
z
= detector background current defined
when the ZERO key was pressed
I
STOREF
= referenced detector current defined when
the STOREF key was pressed
R = responsivity of the detector (A/W)
(or detector with attenuator)
To make relative measurements with background correction, proceed as
follows:
a. Select the REL measurement mode, auto-range, and a wavelength.
b. Block the light to be measured.
c. Select background correction by pressing the ZERO key. Display should
read approximately zero, but will fluctuate depending upon the varia-
tions in the amount of light reaching the detector and the detector dark
current fluctuations.
d. Illuminate the detector with the optical signal to be used as the
reference signal.
e. Press the STOREF key.
f. Illuminate the detector with the optical signal to be measured.
g. Take the reading from the display.