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2.8.3
Making Pulse Energy Measurements
The following process describes the procedure for making basic optical pulse
energy measurements.
i.
Plug in a Newport Energy detector via its associated calibration module
and then turn the meter on. Set MODE to CONT PULSE, set AUTO on and
also set the measurement wavelength to the desired value.
ii. Illuminate the detector and note the display value as the meter measures
each laser pulse. These readings represent the energies of the incident
laser pulses. The meter will display the last pulse energy measured until a
new pulse arrives.
2.8.4
Making a Signal Integration Measurement
The following process describes the procedure for making a basic signal
integration measurement while properly removing influence of ambient light
and other drift effects. The Model 2835-C begins and ends integration via the
arrival of a trigger signal such as is received from the R/S key.
i.
Plug in a Newport Low-Power or High-Power detector via its associated
calibration module and then turn the meter on. Set MODE to DC CONT, set
AUTO on and also set the measurement wavelength to the desired value.
ii. When using a Newport High-Power (thermopile) detector, execute AUTO
CAL per Section 2.4.4.
iii. Cover or otherwise block the source that you will be measuring, turn ZERO
on and then set the MODE to INTG. As you enter the INTG mode, the
meter will begin to acquire and integrate data. The display value may
reflect the integration of noise due to ambient temperature fluctuations
(thermopile) or light fluctuations (photodiode).
iv. Uncover or trigger the source. The display value should now reflect
detector signal integration process by continuously increasing.
v. Press the R/S key to stop the integration and freeze the display value at the
final integration value.
NOTE
1. The process as described above assumes that ambient signals are not
changing between when you zero the display and when you make your
measurement.
2. The 2835-C will not integrate signals less than 10 pA. If your noise level is
greater, the ZERO command may help (step iii).
2.8.5
Measuring a Laser Pulse Energy with a Thermopile Detector
This application makes use of the Model 2835-C’s INTG mode. When an
optical pulse with energy
E(
λ
)
is incident on a thermopile, a voltage signal
arises as the heat pulse flows out to the cooling fins. The integrated signal
resulting from this heat pulse is a measure of the optical pulse energy. See
Figure 8.
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