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Friday, April 1, 2011

study of digital planimeter


study of digital planimeter

Aim:
            To measure the area of the plan in the drawing sheet.

Instrument:

            Digital Planimeter

Measurement Procedure:

1. Preparatory Steps:
            Level and paste the object on a drawing board placed nearly horizontal. Set the instrument with its roller with and tracer arm placed at right angles to each other and placed the tracer arm on the approximate centre line of area of the object.

2. Power On:
            Push the on/c key. The display will indicate `O'.

3. Selection of Metric or English scale:
            Push the m <= = => ft. key and the unit of metric system are displayed alternately on the right side of display. Select and set either unit symbol. (If no unit symbols appear on power turned on, it means that the instrument is in the pulse count mode. Push the unit key, making the selected unit symbols displayed).

            The unit km2 (or acre) is followed by no unit symbol but the pulse count mode. In this case the pulse is equivalent to 0.1 cm2 for areas on a 1:1 scale.

            Once set, the unit system and it's symbol will be protected even after the power is turned off unless the m <= = => ft. key and the unit key are pushed.

4. Selection of Unit:
            Each time the unit key is pushed, the mark shifts to the higher unit [namely cm2 (in2)] to m2 (ft2) or m2 (ft2) to km2 (acre) and eventually returns to the lowest thus repeating that sequence. Set the selected unit when the mark reaches it.

5. Tracing of an area:
            Mark the starting point at any position on the outline of area to be measured. Set the pin point of circle in the tracer lens on it. Push the START key and see that `O' appears on the display (with a sound `beep'). Then move the tracer clockwise along the outline of area until it comes to the starting point. The figure displayed indicates the area of object that has been measured.

6. Memory of Measured Figures by HOLD key:
            The measured figures on the display are frozen by the HOLD key. In this mode, both the `HOLD' symbol appear on the left side of the display unit. This prevents an inadvertent loss of result when it is memorised.

7. Accumulative Measurement by HOLD key:
            The HOLD key may be used to accumulate segments of a large area or measure two or more different areas accumulatively. To measure and accumulate several areas trace the first area and push HOLD key, then trace the second and push the HOLD. Repeat the some steps for third, fourth etc...

            To start a new measurement during accumulative measurement after releasing the `HOLD' function by the second or any subsequent push on the `HOLD' key, return the tracer to the original starting point and push the ON/C key then the figure frozen at the previous measurement appears on the display unit.

8. Average Measurement by AVER key:
            The same area measured repeatedly up to nine times may be averaged to obtain the most reliable results.

            Measure an area, push the END key, and measure the same area again. Repeat this procedure continuously several times. Eventually, push the AVER key to obtain the final averaged result.

            Pushing the END key causes the display to become "O". This value is not frozen but changes as the tracer moves. If the "O" display changed when the tracer was aligned the starting point to make the second measurement, push the ON/C key to bring the display to "O". In this condition, the data effective before the END key was pushed is stored and only the figure in display is cleared, permitting average measurement to continue.

Result:

            The area of the given plan       =

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