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Description
Improved Polar Planimeter, German silver,
adjustable tracer-arm about 8 1/2" in., fully graduated, with vernier and clamp
with slow-motion screw; ball-pole, pole-weight and balancing weight; with
Testing Disc and table of settings for inches and metric measure; in leather covered
,velvet lined case, accommodating the instrument when set to any scale.
Details of use
The tracer-arm is fully graduated, very fine settings can be effected with great accuracy for any scale in U. S. Standard or any foreign measurement, and allowance can be made for the shrinkage of drawings. The tracer-arm is also provided with index marks for a number of scales for Inches and Metric measurements. The Testing Disc greatly facilitates the rapid finding of these settings, and also serves to prove the accuracy of the instrument and as an aid in adjusting it. By shifting the pole weight, which is smooth underneath, the measuring wheel can be easily set to zero. The different parts of the instrument are adjustable and provided with set screws, so that corrections can be made to instrumental errors.
Special Feature; Mean Height of Curve
There are two fine steel points, one attached to the upper side of the tracer
arm, and the other to the surface of the carriage in which this arm slides. The
fine steel points when not in use are protected by German silver caps
These two points are used to obtain the mean height of a diagram, hold the planimeter up-side down and adjust these points so that the distance between them shall coincide exactly with the length of .the diagram, then clamp the arm and proceed in the usual way exactly as if the area of the diagram were sought. Instead of giving, however, the area, the setting of the tracer arm is by this means such that the difference of the readings at the beginning and end of the operation, divided by 0.4 is the mean height of the diagram in inches.
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