DE1549811B1 - ARRANGEMENT FOR CONVERTING THE COORDINATES OF A PROBE MOVED OVER A SURFACE INTO ELECTRICAL SIGNALS - Google Patents

Description

The invention relates to an arrangement for reversing accuracy and the reliability of an arrangement Conversion of the coordinates of a surface to convert the coordinates of a moving probe into electrical signals with a surface moving probe into electrical signals of the Surface resistance layer, which can be used to improve the probe type mentioned at the beginning, is moved to receive signals, with a 5 To achieve this object, the invention provides first AC voltage source for feeding a before that the first AC voltage source to the AC voltage of a predetermined first frequency in one strip of the first pair of contact strips a first pair of contact strips, which supplies par alternating voltage to each other, which is opposite to the allele run and on opposite to each other the other strips of the first contact strip pair Side of the surface resistance layer in electrically supplied alternating voltage a constant phase centric Contact with the same are arranged with a difference that in the same way the second a second AC voltage source for feeding AC voltage source to the one strip of the Solution of an alternating voltage with one of the first second contact strip pairs an alternating voltage Frequency different second frequency in one delivers which opposite that on the other strip second pair of contact strips, the alternating elements supplied parallel to one another 15 of the second pair of contact strips and has a constant phase difference to the first pair of contact strips in an angular voltage, kel run and on opposite sides that the signal picked up by the probe in Sides of the surface resistance layer in electrical a filter in the two frequency components Shem contact are arranged with the same, and corresponding partial signals is broken down, which are separated with a filter for separating the different in 20 are each fed to a phase discriminator Signal existing frequency components. the one, which the respective phase position of the partial signal From the United States patent specification 2 241544 there is a reference to the phase position of a reference signal Order for converting the coordinates of a determined and one of these phase difference propor- ([ A probe moved across a surface is generated into electrical tational voltage, which is used as a measure of the Signals known in which the coordinates of the 25 special coordinates are displayed. Position of the probe at any point in time through the An advantageous embodiment of the invention

Amplitudes of the recorded by the probe provides that the first pair of contact strips to the Signal components of different frequencies shown second contact strip pair runs vertically and The principle of operation of the circuit is that the strips at the edges of a rectangular shape is based on that the amplitude of a composite 30-shaped surface of the resistive layer is arranged nent frequency signal from the location of the probe in.

the one and the amplitude of the other compo- A preferred development of the invention

nenten frequency signal in the same way from the current arrangement is achieved in that Position of the probe in the other coordinate direction is the alternating voltage applied to one strip is dependent. 35 opposite that on the opposite strips

In practice, the output signal from the applied AC voltage becomes a phase difference Filtered probe, and the two frequency components of 90 °.

ten are separated, are then from a major advantage of the invention

on the other hand separately amplified and rectified, the device being representative of previously known arrangements, the resulting direct current signals for the coils for converting the co-ordinates of an overdimensional data of the position of the probe. These a surface-moving probe into electrical signals signals can be further processed in any way resulting from the fact that the accuracy as well as, for example, the reliability of the device entered into a computer does not depend on the or an imaging device such as a signal amplitude, which depends on the movement i cathode ray tube are fed or even 45 g _gun of the probe serve as control signals over the resistive layer by '. change the most varied of interfering influences in an uncontrolled manner

The known device has two main features. The system according to the invention has disadvantages. The first disadvantage is that its accuracy, as well as its reliability, has a single-range ratio of the amplitudes of each frequency, Hch of the phase of the recorded signal that must be achieved when the probe is in the 50 dependent on which one is measured, so that the signal ordered coordinate direction can be fully amplified before its phase is measured This range of motion is moved, becomes unfavorably large.

must be, if the resolution of the circuit is due to the fact that the phase measurement with per se known digital

should be sufficiently good. Thus, for example, the valley method of phase comparison must be able to be carried out in a particularly simple manner in an amplitude range ratio of at least 100 to 1 55, if the accuracy of l ^e / o can be achieved the measurement result is in digital form, so that it should. The second disadvantage can be seen in the fact that the direct input into a digital data processing system for changes in the component signal amplitude system has advantageous possibilities for further processing due to causes other than the movement of the probe. processing offers.

for example by changing the spacing of the 60. The invention is hereinafter exemplified by Probe from the resistive layer over which you hand the drawing described, is moved, adversely affect the accuracy. The drawing shows a simplified block diagram

Such changes in the spacing of the probe from one embodiment of the invention, the resistive layer can, for example, by

Non-uniformity in the thickness of the insulating layer, the arrangement for converting the coordinates normally used to protect the resistive layer of a probe moved over a surface into an electrical one arranged over it. Signals with a base plate A, e.g. B. a glass plate,

The object of the invention is to provide a qua-

Dratic plate with a side length of assumed 25 cm, on which a thin layer (not shown separately) of a suitable resistor material is applied. The connection to the resistor material is made by means of two pairs of contact strips Zl-Z 2 and Yl-Y 2, which run along the sides of the square, the strips of each pair being parallel to one another. To protect it, the applied resistive layer is covered by a hard insulating layer over which a probe P can be moved, which is capacitively coupled to the resistive layer through the insulating layer in any position of the probe.

Two alternating voltages of different frequencies / 1 and / 2 are supplied from sources 1 and 2, respectively. The voltage from the source 1 is fed directly to the strip X1 and via a 90 ^ phase shifter 3 to the strip Z 2. In the same way, the voltage from the source 2 is fed directly to the strip Y 1 and via a 90 ^ phase shifter 4 to the strip Y 2. The output signal picked up by the probe P is broken down into its two component frequencies. This is done by frequency-selective amplifiers 5 and 6, which are selective for the frequencies / 1 and / 2, respectively. The output signal from the amplifier 5 is fed to a phase discriminator or detector 7, which is also fed with a reference phase signal which corresponds to the signal on one of the strips Zl or Z 2, as shown on the strip Zl. In the same way, the output signal from the amplifier 6 is fed to a phase discriminator or detector 8, which is also fed with a reference phase signal which corresponds to the phase position of the signal on the strip F1. The signals representative of the coordinates of the probe appear at the output terminals 9 and 10, the one at terminal 9 being dependent on the phase position of the recorded signal of frequency / 1 and therefore on the position of the probe in the coordinate direction Z1-Z 2, while that at terminal 10 is dependent on the phase position of the recorded signal of frequency / 2 and thus on the position of the probe in the coordinate direction Y1-Y 2 . If necessary, amplifiers and amplitude limiters (not shown) can be provided. This is done according to known principles in order to ensure that the phase discriminators work as independently as possible of the input amplitudes and only as a function of the phase positions of the input signal.

As can easily be seen, the above-mentioned errors of the known circuits are caused by the arrangement according to the invention greatly reduced, which also shows the further advantage that phase measurements offer themselves for further digital processing, so that the useful signals are sent to the Terminals 9 and 10 can easily be shaped to be digital and thus for direct entry in a computer are well suited.

Claims (3)

Patent claims: 1. Arrangement for converting the coordinates of a probe moved over a surface into electrical signals with a surface resistance layer over which the probe is moved to receive signals, with a first AC voltage source for feeding an AC voltage of a predetermined first frequency into a first pair of contact strips , which run parallel to one another and are arranged on opposite sides of the surface resistance layer in electrical contact with the same, with a second AC voltage source for feeding an AC voltage with a second frequency different from the first frequency into a second contact strip pair, which are parallel to one another and extend at an angle to the first pair of contact strips and are arranged on opposite sides of the surface resistance layer in electrical contact with the same, and with a filter for separating the various frequencies present in this signal nz components, characterized in that the first alternating voltage source (1) _{supplies an alternating voltage to one strip (Z 1} ) of the first contact _{strip pair (Z 1} , X ₂ ) which is opposite to that of the other strips (Z ₂ ) of the first Contact strip pairs supplied AC voltage has a constant phase difference that in the same way the second AC voltage source (2) to the one strip (Y ₁ ) of the second contact _{strip pair (F 1} , F.,) supplies an AC voltage, which compared to that on the other strips (F,) of the second contact strip pair supplied alternating voltage has a constant phase difference that the signal picked up by the probe is _{broken down in a filter in the two frequency components (Z 1} and f. ₂ ) corresponding partial signals, each separated in a phase -Discriminator (7, 8) are supplied, which determines the respective phase position of the partial signal with respect to the phase position of a reference signal and this it generates voltage proportional to the phase difference, which is displayed as a measure for the probe coordinate. 2. Apparatus according to claim 1, characterized in that the first pair of _{contact strips (Z 1} , Z ₂ ) to the second pair of contact _{strips (F 1} , F ₂ ) extends perpendicularly and that the strips at the edges of a rectangular surface of the resistance layer are arranged. 3. Apparatus according to claim 1 or 2, characterized in that the _{alternating voltage applied to one strip (Z 1} or F ₁ ) has a phase difference of 90 ° compared to the alternating voltage applied to the opposite strip (Z ₂ or F ₂₎ . 1 sheet of COPY drawings