s.o.l. meter
Speedometer Input

the main

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the s.c.r.e.a.m.

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the r.e.t.a.r.d.

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the s.o.l. meter

 - overview
 - car modification
 - meter design
 - meter input

I. Overview of Situation

    When the s.o.l. meter was designed (see [1]), it was assumed that the speedometer's relation between voltage and speed was linear. At this time, this seemed a reasonable assumption, as all the data taken had been for speeds under 40mph. However, when readings were taken of above 50mph, it became clear that the curve was, in fact, not linear. This presents a large problem, as the speedometer's inputs will need to be modified in some way to provide a linear relationship.

II. Determination of Waveform

    As no oscilloscope was present when the data were obtained, only certain readings could be taken: DC voltage, AC voltage, and duty cycle, all measured against speed. The data were then transformed into more helpful plots using MATLAB. The figures below show the different results.

Figure I. D.C. voltage plotted against speed.

Figure II. A.C. voltage plotted against speed.

Figure III. Duty cycle plotted against speed.

    It should be noted that the set of data obtained is far from complete; duty cycle and A.C. voltage measurements are very lacking. It is also of extreme importance to note that in Figures 2 and 3, the measured speed values start at 55 mph (which is near the top of the parabola in Figure 1); Figure 1 readings start at 20 mph. However, the figures still hold valuable information. Unfortunately, though, until an oscilloscope is obtained and used, the true nature of the waveform cannot be known.

III. References

[1] http://www.igglybob.com/projects/sol_meter/meter_design.php