GB1245764A - Improvements in or relating to test equipment for electrical or electronic devices - Google Patents

Abstract

1,245,764. Sorting. SIEMENS A.G. 26 Sept., 1968, No. 45762/68. Heading G4H. [Also in Division G1] Apparatus for testing an electrical characteristic of a device P ascertains the variation of the characteristic as a parameter of an applied input signal varies within a certain range, and then produces a pulse train whose length is representative of the characteristic over the range. The pulse train may be related to the minimum or maximum value of the characteristic over the range tested, or to an intermediate value. In the example given P is a filter whose frequency response is to be investigated. A generator G supplies to the filter a test signal U1 whose frequency is varied periodically over a certain range. The output U2 of the filter is applied to a measuring instrument Lm via a damping circuit T3 which damps the oscillations of the moving element Mw of the instrument. A light beam is reflected by a mirror Sp, mounted on the moving element, on to a scale Sk, along which are mounted pairs of photodiodes a-m, the diodes of each such pair being connected to respective measuring units M1, M2, and limit photodiodes n, o. On setting the test signal generator G in operation the light beam sweeps past the lower limit diode o producing a pulse which, by triggering a timer unit T1, renders units M1, M2 inoperative for a predetermined period to allow transient effects to die away. A test period follows in which unit M1 ascertains which of the diode pairs are swept by the light beam during the periodic variations of the test signal frequency. On termination of the test period the damping circuit T3 is disconnected from the instrument so as to cause the light beam to return rapidly to zero. In doing so it sweeps a certain number of diode pairs, and the second diodes of these pairs supply pulses to unit M2 which, however, under the control of unit M1, inhibits the response of diodes in those pairs which responded during the test period. Thus a pulse train is generated the number of pulses in which is a measure of the lowest point to which the light beam was sweeping during the test period. The pulse train and/or the range of variation of the characteristic during the test period may be used to control apparatus for sorting the devices into an appropriate category. Automatic fault indications are given if diode o is not swept by the light beam at the beginning of a test, or if the upper limit n is exceeded.