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EE372 Test 4
1.
Reference the textbook problem 6.12. Design a system using the
photoconductive cell in Figure 6.9 to measure and display light intensity. Make
the design such that 20 to 100 mW/cm2 produces an output of .2 to 1.0 V.
What is the readout error when the intensity is 60 mW/cm2?
2.
A single silicon photovoltaic cell is found to have an open-circuit voltage of 0.6
V and a short-circuit current of 15 mA in full sunlight. Show how a collection of
these cells can be arranged to deliver 500mW at 9.0V into a load. Write a
verbal description of your solution.
3.
In a turbidity system such as that of Figure 6.34, the tanks are 2 m in length. A
laser with a 2.2-mrad divergence, 2.1-mW power, and 1-mm exit radius is
employed. If the sample nominally detracts from the beam power by 12% per
meter, find the intensity of the beam at the detector. The laser is 1.5 m from
the beam splitter. Note that the splitter halves the power and does not affect
the divergence.
4.
Reference the textbook problem S6.2. An automatic security camera must
operate as follows when an intrusion occurs: 1. If the ambient light level is
greater than 20mW/cm2, the shutter is activated. 2. If the ambient light is less
than 20mW/cm2 a light source is triggered. 3. When the source lighting
reaches 20mW/cm2, the shutter is triggered. Design the system and signal
conditioning using the following assumptions:
a. The shutter and light source are triggered by TTL logic high signals.
b. A CdS cell with characteristics given in Figure 6.9 is used to monitor
ambient light level.
c. A photodiode with the characteristics given in Figure 6.16b will be used to
measure light intensity after the light source is triggered. Explain why the CdS
cell could not be used here also.