Characteristics of handwriting

Life_times_of_ball_point_pensBall point pens are reputed to be able to deliver substantial contour lengths of writing. Contour length in this context means the distance travelled by the tip of the ball point. This involves a substantial amount of writing! It would be difficult for a single person to test a number of different ball point pens, both from the time involved and the difficulty of maintaining a comparable writing style over the prolonged periods. We probably need a machine and this means we need to understand the characteristics of handwriting.

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The availability of input devices, such as digitising tablets, have enabled scientists to identify the key parameters in the space and time trajectories of a pen tip during writing. . In essence, the tablet provides a sequence of spatial coordinates as a function of time. We can use these to evaluate the typical velocities, as well as the changes of direction and acceleration per stroke. A stroke is defined as a movement terminated by two zero velocity points. Such points correspond to a change of direction.

We and others have found the maximum writing velocity of handwriting is typically around 70-100 mm/s. The acceleration during writing varies greatly with a maximum in the range of 1500 to 2000 mm/s2. The maximum speed and acceleration in your handwriting will depend on your age and sex. We have developed a machine system which subjects the pen under test to the same characteristics of velocity and acceleration as well as the typical downwards force we apply when we write with a ball-point pen.

We record the 'writing' on a standard paper surface which we examine using optical as well as spectroscopic imaging techniques. We use this approach to measure the contour length of the writing before the pen fails or runs out.

This research involved Professor Geoff Mitchell (CfAM) and has been funded in part by BIC.

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