The Polar Planimeter.
Carriage, Carriage Vernier and Attachments.
The frame or Carriage C of the instrument
carries the Integrating Wheel W together with the recording mechanism
and the necessary adjusting screws. As already stated
the Polar Arm is connected to the Carriage by the pivot F, while the Tracer
Arm passes through sleeves or bearings on the Carriage which allows the
Arm to slide backward and forward or to be rigidly clamped to the Carriage
at any desired point by means of a binding screw L. Attached to the Carriage
is a Vernier V called the Carriage Vernier, so situated as to allow
the graduation of the Tracer Arm to work along its edge, and by its use
the smallest division of the graduation is still
further subdivided into ten smaller parts which in this case are one two-hundredths
of a millimeter. By this arrangement the Zero of the
can be brought very near to any desired point on the graduated Tracer Arm,
the binding screw L tightened and the exact adjustment made by means of
the slow motion screw M.
The exact point on the Tracer Arm to which for any given operation the
Zero of the Carriage Vernier is required to be brought or set is,
has already been mentioned, both definitely located and recorded by
expressing its position in terms of the unit of the scale of equal parts
engraved along the edge of the Arm, and the point thus located and record
for any given operation is called the Setting for that operation.