Product Manual

Example Of A Model 10 / 20 Calibration Record
6.3 DETERMINATION OF THE AREA MEASURING CONSTANT C
A
.
After finishing the measuring operation, the readout result must be multiplied by C
A
in order to obtain the true area value.
For 1:1 Measurements, C
A
= u ; i.e. the user simply multiplies his or her
readout result by the u-value of the instrument in use. If the instrument is a fixed
arm model 10 or 20, the u-values can be obtained from the Calibration Records
(see example shown above).
If the instrument is a model 30, it is necessary to use the u-value specified for the
tracer arm extension used. (please check the previous page) .
Example:
A figure is to be measured directly in sq.inches. The instrument used is a Mod.
L10.
The u-value for a Model 10 is 0.01. Subsequently all readout results must be multi-
plied by 0.01 in order to obtain the result in sq. inches.
If the readout result is 4562, the true area result is 4562 x 0.01 = 45.62 in
2
;
Models
10 / 10A
20 / 20A
20M /20AM
u-Value (English)
0.01 in
2
0.02 in
2
0.015 in
2
u-Value (Metric)
0.0645 cm
2
0.129 cm
2
0.1 cm
2
Page 7
For Measurements of Scaled Areas, the C
A
value must be determined.
The following formula applies: C
A
= Sc
2
x u ; where Sc is the scale ratio
expressed as an engineering ratio.
Again, the u-value entered into this formula is always the same if a model 10 or 20
is used.
However if the instrument is a Model 30, it is necessary to use the u-value speci-
fied for the tracer arm extension used. (please check the previous page) .
Example:
The square footage of a land parcel is needed. Scale ratio is 1"= 40' ; The Plani-
meter model used is a L 30 with medium arm extension.
Therefore C
A
= 40
2
x 0.01368 = 1600 x 0.01368 = 21.89 ft
2 ;