Electronic drafting instrument with digital readout of displacement

DETAILED DESCRIPTION This invention is a straightedged drafting instrument which measures its own displacement as it is moved over a drawing media and reads out the results on a large easy-to-read digital display.
The display is mounted directly to the instrument near its leading straightedge so the user does not have to look away from the drawing to read the display.
The body of the instrument is a flat plate-like chassis or compartment which houses one or more drive wheels, a direction sensing displacement sensor such as an optical or electromagnetic direction sensing rotary incremental encoder, a pulse processing circuit comprised of an up-down counter and a calculator type circuit, a scale factor keyboard, a digital display such as the liquid crystal, light emitting diode, or electrofluorescent type, and a contact sensor and annunciator.
The direction sensing displacement sensor is driven by one or more wheels or rollers which are mounted to the plate and which turn when the plate is moved over the drawing media.
The wheels are mounted to the plate such that the plate is lifted slightly above the drawing surface and may be moved about without smearing the drawing.
The direction sensing displacement sensor produces electronic pulses as the plate is moved and the number of pulses is proportional to the displacement of the plate.
The number of pulses from the sensor is processed by the combination up-down counter and calculator-type circuit, and readout on the digital display.
The display may be reset to zero at any time via the keyboard.
The keyboard also allows the user to select any scale factor or length unit desired.
The total length which can be measured is limited only by the number of digits which can be readout on the selected display.
The smallest distance which can be measured is determined by the resolution of the rotary incremental encoder and 0.
010 to 0.
005 inch would be typical.
The calculator part of the pulse processing circuit may be used independent of its pulse processing function