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Direct Reading Accelerometers. 



By C. R. Moore. 



Every person is more or less familiar with the subject of acceleration 

 or deceleration — changes of velocity — whether or not the laws governing 

 the same or the mathematical expressions therefor are understood. Such 

 everyday occurrences as passengers swaying to and fro partially suspended 

 from street car straps, the hurry up that accompanies one's movements as 

 he tries to reach the car door just as the motorman stops the car, are 

 examples which prove this. Changes in the rates of motion are essential 

 to all forms of transportation, and the more rapidly a car or train can be 

 brought up to speed (or stopped) the shorter will be the time required be- 

 tween two points when a given number of stops must be made. Railway 

 trains, street and interurban cars are therefore started and stopped as 

 quickly as is consistent with reasonable comfort, in response to the demand 

 of the traveling public for fast time. 



It is the purpose of this paper to discuss briefly the laws of motion, 

 and to describe a new device for measuring the rate of change of velocity, 

 showing results of tests recently conducted in the Electrical Laboratories 

 at Purdue University. 



The author realizes at the outset that the subject of acceleration 

 measurement is an old one and is rather reluctant to lay claim before this 

 body of scientists that what is offered herein is new. However as far as 

 his knowledge goes this device has not been used previous to this time. 

 The scheme is brought to your attention for whatever consideration it may 

 merit. 



Before discussing accelerometers in detail, a brief study of just what 

 is meant by acceleration and deceleration may be of value. 



In Fig. 1 curve "D" shows distances plotted against time, the dis- 

 tances being taken as ordinates and the time as the abscissa?. The car is 

 to be thought of as moving from a certain point "O," distances "d" being 

 measured from that point at the end of the any time "td." It will be noted 

 that during the first few time units after the car starts the distance passed 

 through each successive unit is greater than that passed through during 

 The preceding unit of time, i. e. the rate of motion is increasing. At the 



