Product Manual

7. INSTRUMENT TESTING AND RECALIBRATION
Any area of known size can be used for instrument testing or recalibration. However
since freehand tracing will inevitably introduce tracing errors, it is essential that
multiple tracings are performed and averaged .
page 9
7. 1 Test Procedure
We recommend to draw a 4 x 4 inch
square if your instrument is calibrated
for English (imperial) measuring units
or a 10x10 cm square, if you use the
metric system.
Measure the area as outlined on page
1.
Obtain the readout result "N" from the
measuring mechanism
Multiply the readout (N) of
Model 10/10A by 0.01
Model 20 / 20 by 0.02
Model 20M/20AM by 0.1
Model 30 by the u-values shown in the
calibration records. (depending on arm
extension used.)
The results must be 16 in
2
for instru-
ments calibrated in English units and
100 cm
2
for metric planimeters.
TRACER ARM
LOCK SCREWS
Fig.10
7.2 Instrument Recalibration
The planimeter can easily be recalibrated
by the user. Recalibration may become
necessary if an instrument was dropped
and knocked out of adjustment or if the
Calibration Records were lost.
You may recalibrate by drawing a precise
square or rectangle on a sheet of paper.
(we recommend to draw a 4x 4 inch or a
10 x 10 cm square.)
Models 10/20 :
Measure the test area and multiply re-
sult (N) by your u-value.
If the result is too low, reduce the
length of the tracer arm, if it is too high,
lengthen it.
Subsequently, slightly loosen the two
tracer arm lock screws on the bottom of
the planimeter (Fig.10). Lengthen or
shorten the arm length depending on
the result obtained before . Measure
again, etc. Repeat until result is ok. Se-
cure lock screws again.
Model 30 :To find the tracer arm settings
for 1:1 measurements, we proceed as
outlined.
Measure the test area and multiply the
readout result " N " by u= 0.01 (English)
or by u=0.1 (Metric)
If the result is too low, reduce the tracer
arm length, measure, change arm length
again, measure, etc. until result is ok.
Record the setting of your arm.
If the measuring result was too high,
lengthen the arm. Repeat this procedure
until the readout result multiplied by u
equals the value of your test area.
For Scale Measurements using short,
medium or long arm extensions, we
must determine new u-values.
Select the short tracer arm extension.
Measure the test area. Readout result is
designated as "N" ;