Hands On Physics

Core Project Activities

How the Sun Photometer Works:

Pictured below in Figure C1, is an electronic circuit diagram of the Sun Photometer. The triangle marked "741" is an operational amplifier. In operation, light from the sun causes the LED detector to generate a tiny electrical current much like a solar cell does. This signal is amplified and read with a voltmeter.

Figure C1
Haze Detector Circuit

The 741 operational amplifier is connected to the LED so the small current produced by light shining on the LED is transformed to a voltage and amplified. The voltage is boosted by the amount of the feedback resistance in ohms between the input (pin 2) and output (pin 6) of the amplifier. If the feedback resistor has a resistance of 3,900,000 ohms, the amplifier boosts the signal from the LED by a factor of 3,900,000. The voltage from the amplifier is measured with a digital voltmeter.

The core activity of this unit is building a sun photometer.

This task has been broken down into several sequential activities which lead to a completed scientific instrument for measuring haze in the atmosphere.

Sun Photometer Assembly Instructions

As soon as the sun photometer has been assembled, you can begin taking data. To make the data usable, however, this photometer must be calibrated.
How to Calibrate the Sun Photometer

A well-build and properly calibrated sun photometer is a scientific instrument which can be used repeatedly for gathering information about haze.
Using and Maintaining the Sun Photometer

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