ANSWERS TO FREQUENTLY ASKED QUESTIONS ABOUT PLANIMETERS
What is a Planimeter?
Basically speaking, planimeters are area measuring
tools. Planimeters are precision instruments used to
trace around a closed loop of an object to find its
area. Planimeters are used by engineers, surveyors,
contractors, designers, medical professionals, and
more. The "closed loop" that we mentioned can be the
outline of a storm pond, a tumor in a human organ,
the outline of a odd-shaped swimming pool, or the
area of leather in a shoe. Yes, we had someone
measuring each piece of leather in a shoe once it
had been worn and disassembled. The person wanted to
find out how much each piece of leather had
stretched after being worn to figure a percentage of
the stretch that had occurred. They were simply
measuring the outline of each piece of leather
before and after the shoe had been worn. Each week
that passes, we hear of new ways planimeters are
With a planimeter, you set the scale of your drawing
or measurement, then push, pull, or roll the
planimeters head around along the perimeter or
outline of your object and it'll tell you the area
of the loop.
What is the difference between Roller & Polar
Roller planimeters are attached to wheels that allow
unlimited horizontal travel and vertical travel
within the limits of the arm movement. Polar
planimeters are attached to a weighed base by an
arm that allows movement with a circular area. Roller units
offer more versatility since they are not "pinned"
down to your work area. Roller planimeters can roll
all over the place without the restriction of an
attached base and arm like the polar planimeters
Should I buy a Mechanical or Electronic (Digital)
Mechanical planimeters are the most popular types
since they are economical and offer good overall
accuracy and range for most applications involving
medium sized areas. The measuring wheel rides
directly on the measuring surface. It is integrated
into a measuring mechanism with a dial, drum and
vernier readout system with the typical maximum
counting capacity of 4 digits (9999).
However, Electronic Planimeters offer greater
precision, ease of selecting units of measure, have
memory to retain multiple measurements, and some
have the ability to sum multiple areas measured.
Electronic Planimeters are also popular due to their
speed in measuring, and ease of use.
What is the Scale Factor?
The scale factor is the x-scale multiplied by the y
scale. (This must be computed when using the Planix
5 and the Planix 6 because they do not have a
built-in scale computation.) The reading from the
planimeter is then multiplied by this to obtain the
area in the drawing.
What if the area I want to measure is larger than
the reach of the planimeter arm?
All of the Planix instruments have a "hold and
accumulate" feature. Subdivide the area to be
measured into the smaller areas that are within the
range of the unit. Measure each area pressing the
hold key once to stop measurement and once again to
initiate measurement once the planimeter is moved to
the next area.
What direction should I move the tracer arm?
The tracer arm should be moved in a clockwise
direction and returned to the original starting
point. Moving the arm counterclockwise will give you
a negative reading. This can be used to subtract
smaller areas contained in larger ones. See
instruction manual for details.
How accurate are the Planix planimeters?
Planix planimeters have a stated accuracy of 0.2% of
the area measured. For accurate work, Planix
recommends that the work be done slowly and
carefully and the averaging function be used so that
the final measurement will be the result of several
If you're concerned with cost of the product you're
planning to buy, consider the useful life
expectancy. You should consider the price being
spread out over these years and not be as concerned
with price as much as the value and time saved.
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The EngineerSupply.com Product Team