GB975762A - Improvements in or relating to magnetic character testing - Google Patents

Abstract

975,762. Testing characters for automatic reading. CROSFIELD ELECTRONICS Ltd. Oct. 8, 1962 [Oct. 13, 1961], No. 36849/61. Heading G4R. An instrument for testing the distribution or intensity of magnetic ink over a character comprises a rotatable member carrying an electromagnetic head which scans the character, the resultant waveform being displayed on a cathode ray tube for comparison with data derived from standard characters. The document carrying the character is placed face downwards on a platform 1 so that it is repeatedly magnetized by a permanent 7 and then scanned by the head 6 as the drum 3 rotates. The signals are taken off by sliprings and brushes 13, 14 and applied through a variable amplifier to the Y-plates of the C.R.T. Coil 19 generates a pulse during each revolution as the magnet 7 passes it. This pulse is used to trigger the timebase circuit of the C.R.T. The waveform is thereby displayed as a steady trace on the screen. Horizontal lines may be provided on the screen by which the amplitude of the waveform can be compared with standard amplitudes or the waveshapes of standard characters may be drawn on transparent screens to be placed in front of the displayed waveform. A lamp communicates with the character through bores 20 in the drum and the reflected image is displayed by a mirror and lens system for visual inspection. In a modification for testing characters on large webs the web is drawn by suction against the drum and the instrument is adjustable by means of a lead screw to the desired position across the web. If the ink is wet, the reverse side of the document may be sensed the standard waveforms being suitably modified for comparison. If the web is in motion each character is sensed only once and the waveform is displayed on a storage cathode ray tube.