Patent GB-1235304-A (GB)
Title: Improvements in or relating to oscillographic test apparatus
Inventor: MARTIN ERWIN
IPC: B07C5/344
Filed: 1968-09-26
Abstract: 1,235,304. Photo-electric curve reading; electric tests. SIEMENS A. G. Sept. 26, 1968, No. 45763/68. Headings G1A and G1U. [Also in Division H4] In an oscillographic test apparatus in which a curve is produced tracing variations of a characteristic of a device under test with variations in a test signal excursions of the trace within or beyond the limits of a tolerance range are detected and utilized to indicate acceptance or rejection respectively of the device. The embodiment described utilizes a cathode-ray tube oscilloscope on which a curve is traced showing variations of the characteristics of a filter or magnetic core with variation of the frequency of a test signal, the tolerance range limits being determined by the configuration of sets of photo-sensitive diodes. Fig.3 3 shows the arrangement of the latter where the photo-diodes 1 to 8 and 9 to 14, which comprise plug-in units in a frame to allow the limits to be altered, are positioned adjacent the screen B of the cathode-ray tube and establish upper and lower limits E and F respectively as shown in Fig. 1. In operation, a test signal U1 the frequency of which is swept upwardly and downwardly is derived from a source G and applied to a test sample at P which produces a characteristic signal voltage U2. This signal is then supplied via a motor driven device M which adds an adjustable beam shift voltage to the voltage U2 to produce a voltage U3 which is utilized to produce vertical deflection of the tube beam against a horizontal time base which sweeps from left-to-right and from right-to-left in synchronisms with the sweeping of the test signal U1. During testing, the device M operates to shift the vertical position of the trace towards the lower limit F at a fast rate until energization of any of the photo-diodes 9 to 14, or of "catches" photo-diodes 15, 16 by the luminous trace on the screen B occurs. A signal is then produced which is fed via amplifiers V9 to V14 or via V15, 16 and a control device UG to a control device SB which arrests the downward shift and institutes a comparatively slow upward shift in steps each of which is effected after a complete sweep, upwardly and downwardly of the test signal frequency. When, ultimately, the trace impinges on the photo-diodes 1 to 9 (e.g. at the position a Fig.1) the resulting signal output which is fed via amplifiers V1 to V8 operates a control device OG which via control device SB stops further operation of the device M. If at this time the trace is also producing energization of the photo-diodes 9 to 14 (e.g. as shown in Fig. 2) a signal is produced by the control device UG. The control device SB which receives the output of device OG and the output of UG, if any, then operates to produce on an output signal on line ab which indicates an acceptable test sample if an output is received from OG but no output UG and to indicate a "reject" order if an output is received from both OG and UG. The output on line ab may be employed to operate an optical or acoustic indicator and to control the sorting of accepted and rejected test samples. By employing a further row of photo-diodes it is stated that an accptance indication may be produced when only a single very narrow peak of the traced curve exceeds a tolerance limit.