9. If this is not the case, the light level must be adjusted. Remember that adjusting the light
level also affects the visible/IR ratio. Also, increasing the lamp voltage causes the IR level
to drop.
10. When the 100 cd/sq ft level is correct and the ratio acceptable, calibrate the remaining light
levels as follows: slide the blade control all the way to the right and adjust the correspond-
ing detent block on the front of the Light Source. Ignore the visible/IR ratio for the 800,
50 and 6.25 cd/sq ft positions.
Calibrating the Horn
This procedure involves measuring offset and gain.
1. Insert the Horn Extender Plug into the Horn Connector on the B-600 Electronics Unit
front panel. Plug the Horn into the Extender Plug.
2. Connect a DVM across pins 9 and 14 of the Extender Plug (the two on the far right, one
above the other).
3. Slide the Master Camera on the Horn with the shutter blades closed. The DVM should
read less than 1 mv (0.001 volt).
4. If not, adjust the offset: insert a screwdriver in the hole on the right side of the Horn,
toward the front of the Camera. Adjust the Offset control until the reading is less than 1
mv.
5. Open the shutter blades until they are at full aperture. Place the Horn and the Standard
Camera in front of the Light Source set at 100 cd/sq ft.
6. The DVM reading should correspond to the number marked on the Master Camera.
7. If not, insert a screwdriver in the hole on the left side of the Horn, toward the front of the
Camera. Adjust the Gain control until the voltage is correct.
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