Mine Countermeasures Technology (1993) / Chapter Skim
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QP303 .R95 1951 ¢.1 Determination of acceleration by use of accelerometers /
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CONTENTS Introduction Fage Basic Requirements Ll Description of Equipment | | 3 Use of Equipment to Measure Shank Accelerations ly Comparison of Accelerometer and Grapho-Numerical Differentiation Methods 18 Figures l.
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Intraduction In studies of Human Locomotion, linear and angular accelerations have for some time been determined by differentiation of time -- displace= -- ment data. The problems encountered arise in obtaining satisfactory data and in graphically or numerically operating on this data to obtain second derivitives.
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Basic Requirements The dynamic quantities investigated were the angular acceleration of the shank of a normal or prosthetic leg and one component of the linear acceleration of a point on the shank. In order to determine definite requirements to be met by the measuring and recording system it was necessary to consider factors common to dynamic measurements in general.
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Ze 4. Size of Pickup and Method of Mounting Relatively speaking, the shank of a normal or prosthetic leg is quite a small "structure," in regard to both weight and size.
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36 Description of Equipment The equipment selected consisted of three Statham linear accelerometers, two type AP and one type C, two Brush Development Company Model BL-310 Strain Analyzers, and one Brush Development Company Type BL-202 two-channel Brush Recorder. At the inception of the testing program, the type AP accelerometers were on hand and had adequate frequency response and sufficient sensitivity.
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he The instrument is constructed so that when at rest in a horizontal position, the tension in each of the suspending wires is the same and each wire is of equal lengthe Hence each arm of the internal bridge has the same resistance R; the bridge is then in balance and no current flows through the recorder. When subjected to the motion depicted in Fige l-c, the operation of the accelerometer is as follows: 1.
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De In view of the above explanation, it is apparent that the bridge output must be calibrated against some known linear acceler= atione The necessary calibration procedure will be discussed later. A further point to be kept in mind, is that if a single accelerometer is subjected to some general acceleration, only that component of the acceleration parallel to the sensitive axis may be determined.
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Te contains four accelerometer strain gage resistances and two resistances provided internally in the Strain Analyzer. Two arms of the strain gage bridge in each accelerometer were removed from the circuit by not connecting one of the output leads on each accelerometer.
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From page 21... ...
8. motor so that the table top moved vertically with simple harmonic motion.
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