Durable Timing Devices for the Peanut Grading Screen Vibrator1

Peanuts are graded at farmer marketing for value determination. The grading procedure requires kernel sizing which is facilitated with perforated screens oscillated with a mechanical vibrator. The vibrator operates for 20-sec periods and is controlled by a hand-adjustable, mechanical timer. The durability of the timer is unsatisfactory and it frequently fails during a single grading season. Subsequent maintenance and replacement costs prompted the development of two more durable timing units. Solid state timers were utilized in both units. Construction of the two units was the same except a mechanical relay was used for switching in one but a solid state relay in the other. During durability testing, a prototype timing device with a mechanical relay switched on and off 11,020 times over an 8-d period before failing. A timing device with a solid state relay switched on and off 68,621 times over a 22-d period without failing. During field testing, six timing units with mechanical relays and five timing units with solid state relays operated an estimated 6000 cycles each at peanut buying points throughout a peanut harvest season without failure.

Reaction Time of the Fingers with Responses Measured on a Typewriter Keyboard

Reaction times on each of the eight fingers were obtained for 24 skilled typists using an electric typewriter and a mechanical timer. Repeated-measures analysis of variance indicated significant differences among the mean reaction times of the eight fingers. Scheffé's multiple-comparison procedure indicated that the mean reaction time of each finger differed from that of every other finger and that the mean reaction time of the fingers on the left hand was significantly slower than the mean reaction time of fingers on the right hand. The average inter-class correlation coefficient among the fingers was .92 which indicated rank-order of reaction times to be similar across fingers.