Model 1835-C - Newport Corporation

3.8 Integration of Detector Signals
The Model 1835-C provides for making measurements that integrate incoming
power detector signals to obtain an energy via the INTG mode, Section 2.3.12.
In INTG mode, the display units indicate Joules since energy is the time
integral of power:
t1
E λ P λ dt
t0
t1
( )= ∫ ( ) = ∫
t0
()
( )
St
R λ
As the detector signal actually consists of a stream of digitized values, the
integral becomes a numerical approximation using the trapezoid method,
Figure 15. In order to maintain the highest accuracy for this numerical
process, the sample rate is set at its maximum value of 500 Hz.
dt
Detector Signal
Numerical Integration
Trapezoid Method
Magnitude of the
Integraged Result
Figure 15. Integrated Energy Via a Trapezoid Approximation — The INTG
measurement mode performs a discrete integration at a 500 Hz sample rate.
Two common applications are natural extensions of the INTG measurement
mode:
1. Pulse laser energy measurement using with a thermopile detector,
Section 3.5
2. Energy from exposure over a period of time (dosage), Section 3.6.
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