Publicité
Les langues disponibles
Les langues disponibles
Optics
Fibroptonic
Ref : 202 012
1 Purpose
Use a photoreceptor to measure the illumination.
2 Experiment no. 23
The purpose of the experiment described here is to specify the behaviour of the
resistance of the photoresistive "cell" in function of the illumination. It gives simple and
relatively accurate measurements.
Light source 40 W
ENGLISH
FIBROPTONIC
2.1 Equipment:
•
Photoresistor module
•
Multimeter used as an ohmmeter
•
Light source: 40 W to 100 W light bulb
2.2 Set-up and experiment:
•
Connect the ohmmeter to the black and yellow terminals of the photoresistor.
•
Illuminate the photoresistor with the bulb; D is the distance between the bulb and
the photoresistor (figure 26).
•
Vary D by every 10 or 20 cm between 0.20 m and 2.5 m and measure the value
of the resistance R of the photoresistor.
Figure 26: Measuring the resistance R in function of the illumination.
2.3 Results:
Figure 27 shows the shape of the resistance R in function of the distance D for 2 bulbs
of different wattages (40 and 75 W). We observe that R is a linear function of D. Since
the illumination on the photoresistor varies with 1/D^2, we deduce that R varies with
the inverse square root of the illumination thus with 1/E^0.5.
PHOTOMETRY
Photoresistor
68
SHEET
11
Measuring the R to
ohmmeter
Publicité
