The cell is known as a barrier layer type
of selenium cell. A diagram of its ports
is shown in fig. B. When this type of cell
is exposed to light it becomes a self
generating source of electricity. The
reason far this phenomenon is not fully
known. It is believed that under the
impact of light particles (a form of
energy) electrons within the selenium are
freed.
Some of the free electrons move towards the barrier-layer and a greater number towards the metal base. Thus a
potential difference is caused and this results in the flow of a very small electric current. The strength of the
electric current is proportional to the intensity of the light falling an the cell. The current is conducted through a
very sensitive microammetor to which is attached a pointer. The painter is deflected in proportion to the current
Therefore where this deflection is measured against a scale, we have obtained an average value of the intensity
of light or brightness. When the flip-up booster is switched in, the sensitivity is increased 400% and we can
obtain a value in very low level illumination,
1. COVER ( BAFFLE)
2. SLIT
3. RED MARK (Dot)
4. f / STOPS
5. SHUTTER SPEEDS
6. DIN INDEX WINDOW
7. LVS AND EVS NUMBERS
8. CHASER BAR
9. POINTER
10. BLUE MARK (Bar)
11. COVER OPENING BUTTON
12. ASA INDEX WlNDOW-6 to
13. MOVIE CAMERA SPEEDS
14. MOVIE f / STOPS
To Next Page
Loading...
