Prepare the Wires

You will need 8 lengths of #20AWG solid connection wire. You can use one color, but it's less confusing to use 2 colors.

1. Cut these lengths of wire:
   • 7 cm wires: 2 red and 1 black
   • 9 cm wires: 1 red and 2 black
   • 10 cm wires: 1 red and 1 black
2. Next, remove about 5 mm of insulation from both ends of the 2 7-cm wires.
3. Next, remove about 5 mm of insulation from only one end of each of the remaining wires.
4. Finally, remove about 12-15 mm of wire from the second end of the remaining wires.
5. Check the wires to make sure you have cut and trimmed them properly.

Prepare the Switch

Now you will attach 4 of the wires to the screw terminals on the switch.

1. Use a cross-point screwdriver to loosen the 2 center screws and 2 of the screws on one side of the switch. You can select either side. Do not loosen the screws on the remaining side.
2. Find these 4 wires which you previously prepared:
   9 cm red; 9 cm black; 10 cm red; and 10 cm black
3. Form a u-shaped hook in the exposed 12-15 mm end of each wire as shown in Fig. 4 (see "wire + screw"). The easiest way to do this is to wrap the wire around a nail or thin screw driver blade.
4. Refer to Fig. 4 and attach the wires to the 4 terminals. The bend in the hooks of each wire should be oriented in the same direction the screws are tightened (clockwise). Tighten each screw after placing a wire around it.

Prepare the Light Detector

The TERC VHS-1 Sun Photometer uses a light-emitting diode (LED) as a light detector. You must remove the rounded, lens-like end of the LED (Fig. 1) to simplify aiming the instrument at the Sun.

1. Place a piece of coarse 40 or 60 grit sandpaper on a flat surface. Hold the LED by its sides and rub the end of the LED back and forth or in a circular pattern against the sandpaper until the entire rounded section has been removed.
2. Now hold the LED as vertical as possible and rub the sanded end of the LED in a circular pattern until the end of the LED is perfectly flat and level.
3. Wipe away any plastic dust from the end of the LED. Set the LED aside in a safe place until it's ready to install.