Page:Latency of Pupillary Reflex to Light Stimulation and Its Relationship to Aging.djvu/8

6 comparison for each flash of light from the Photic Stimulator two traces were generated on the dual beam Memoscope face, whereby the lower trace showed the analog voltage of the diameter, and the upper trace its derivative. It can be seen that the curve representing the derivative voltage has a much steeper slope than the analog signal of the diameter. The definition with which a single sweep can be resolved on the Memoscope is adequate for measurements within ±3 milliseconds (Figure 5). The readings used for this study were taken from the Digital Recorder. For our purposes, this recorder had an accuracy of ±0.0001 seconds. Figure 5 also shows that the 60 cycle per second scanning rate of the pupillograph modulates the derivative signal.

The timer has a crystal controlled oscillator operating at a frequency of 100,000 cycles per second; for the present application, a 10,000 cycles per second rate was used. A gate in the