1,182,789. Measuring diode recovery; measuring luminescence; measuring magnetic flux. VYZKUMNY USTAV MATEMATICKYCH STROJU. May 3, 1967 [May 3, 1966], No. 20446/67. Headings G1A, G1N and G1U. A system for measuring the time integral of a transiently varying quantity representing the behaviour of a test device during a transient switching process, e.g. measuring the reverse recovery charge of a diode 1 when a reverse voltage is suddenly applied, incorporates conditioning circuits 2 for applying the appropriate switching waveforms to the device 1 under test, a sensing device such as a resistor 31 for producing a voltage output related to the quantity to be integrated and a high speed gating circuit 3. The transitions between the conditions applied to the device, e. g. between a forward current I+ and a reverse voltage U-, are initiated from a repetition generator 7 operating at relatively high frequency 10<SP>5</SP>c/s. This generator also controls the opening of the gate 3 through an interval control 71 to open on the occurrence of the transition but to close before the generator 7 returns the conditioning circuits to their previous condition, to define an integrating interval. The conditioning circuits 2 are switched by a timing generator 8 between main and reference switching cycles at much lower frequency, say 500 c/s, the reference switching being e.g. between O and U-. The output from the gate is passed to integrating and amplifying circuits 9 and 4 and thence to a synchronous detector 5 controlled by the timing generator. This operates to subtract the integrated value determined for the reference switching sequence from that for the main sequence, and this result is passed to the display or indicator 6. A more detailed block diagram (Fig. 2) is accompanied by circuit diagrams for the individual blocks (Figs. 3-13) which are largely unexplained in the description. The system is said to be applicable to determining the quantity of light emitted by a luminescent crystal, the conditioning circuit 2 then being a switchable ultraviolet source and the detector 31 being a photo-multiplier. A further application of the system is to measuring the magnetic flux through a ferromagnetic material upon exceeding the Curie temperature. In this case the conditioning circuit will be a heat source which can be cycled above and below the Curie temperature and the detector is an inductive winding. In measuring reverse recovery of a diode, the repetition generator operates for example in a main sequence according to the timing sequence in Fig. 1(c), defining both preparatory intervals where current Id flows, and working intervals, where reverse voltage U- is applied. The Figure shows a plot of current and the reverse transient to be integrated is shown shaded. The working interval is divided into the integrating interval, fixed by unit 71, and a safety interval. In a reference sequence there may be no switching, to ascertain if there is any steady reverse current.