Method and device for electronic control with positive safety

An electronic device for positive safety control which serves to carry out a method of control of a protection system, in particular for a nuclear reactor, in which N measurements of either one or a number of physical quantities are taken and processed by N matching and/or computation units, wherein the median of the N signals corresponding to the N measurements is selected, said signals being obtained at the output of said units, and wherein the value of the median is compared with a reference value so that the comparison initiates the desired protection action, and wherein said device comprises:

• N inputs derived from the N matching and computation devices which deliver direct-current signals,
• N direct-current to alternating-current converters, each converter being connected in series with each input for converting the direct-current input signal to a periodic signal having a frequency f and an amplitude which is proportional to the direct-current input quantity,
• a supply A' which delivers a periodic signal having a frequency f into the N converters by means of an isolation transformer,
• an alternating current median-determination circuit A containing means for selecting the median of the amplitudes of the periodic signals delivered by the converters, and
• an alternating current comparator for comparing said value Vm of the amplitude of the median with a predetermined direct-current reference value Vr and delivering by means of an isolation transformer a logical signal +1 when Vm - Vr>0, and 0 when Vm - Vr<0, each of the elements of the device being designed for positive safety.