Siemens Aktiengesellschaft

Bernd Kusserow

Klaus Gagneur

Siegfried Hofler

Karl Hudek, Deceased

A protective circuit for a power pack for exciting or de-exciting a superconducting system has a voltage monitoring circuit at the output of the power pack. A switch in parallel to the output of the power pack is closed by the voltage monitoring circuit as soon as output voltage exceeds a predetermined value in a direction opposite a supply voltage of the power pack. During a malfunction, the switch closes and conducts the current which is being driven by the superconducting coil system. The protective circuit can be utilized in devices such as superconducting magnets of a tomography apparatus.

Protective circuit for a power pack for excitation or de-excitation of a

In an exemplary embodiment, the simultaneous intensity control of the individual current circuits is to be effected while avoiding undesired intensity deviations in the current circuits such as occur because of nonuniformity of multiple potentiometers, for example. Expediently, the signal frequencies are digitally generated. According to the disclosure, in every output current circuit a transistor is connected-in, which is switched between a conducting and a nonconducting condition so that the collector output exhibits either a zero value or an operating voltage value, all switching transistors being activated on the collector side via a common control element from a single voltage source. In the through-connected state, the collector voltages of the switching transistors have the same value, respectively, which can be synchronously varied in dependence upon the setting of common control element.

Electromedical apparatus for interference current treatment

In the case of current stimulation apparatus, in particular, protection installations are necessary which, in every instance, disconnect the patient from the operating voltage of the apparatus when maximally permissible patient currents are exceeded. For this purpose, for example, safety fuses or also electromagnetic disconnection devices (relays) are known. In accordance with the disclosure, a safety circuit for disconnecting the patient output from the operating voltage is employed as the protection installation which also responds when the patient current deviates from a preselected desired value adjusted on an intensity adjustment member. For this purpose, an output stage as current waveform generator for constant-current stimulation current is connected with the safety circuit.

Electromedical apparatus

Here, a means is to be created with which quick alterations in the signal behavior are grasped and displayed. Even with the use of peak value meters with very large time constants, such quick alterations are also to be used for the quick correction of the peak value display. In an exemplary embodiment, each separately registered current or voltage value from an individual current or, respectively, voltage circuit is compared at a comparator specifically allocated to it with a mean value which is formed from the current or, respectively, voltage values of all participating current or, respectively, voltage circuits. Upon nonequality of the current or, respectively, voltage values with the mean value within a predeterminable limit, the output signals of the comparators are then brought to display at a separately allocated display element. The invention is used particularly for the measurement of the peak value of middle frequency currents in middle frequency current circuits in electromedical interference current therapy.

Method and apparatus for the measurement of electric currents and/or

In an illustrated embodiment an analog signal is sampled by means of a bucket brigade store. The stored samples are then repeatedly cycled through the store during refreshment of a visual display via a controlled amplifier. The storer also receives a reference voltage sample which is also circulated and which is periodically sampled at the storer output and compared with the input reference voltage, any deviation being utilized to control the amplification of the amplifier to maintain the reference voltage sample at substantially a constant level, and thus to maintain essentially unity amplification during the cyclical operation of the storer. The reference voltage sample can be selectively obtained from the measured signal or by means of a separate reference voltage generator. In the latter instance, the reference voltage sample is to be blocked so as to avoid display thereof, a previous sample of the measuring signal, for example, being displayed instead. For example, a scanner switch at the output of the bucket brigade storer may alternativey supply successive signal samples to the display and the reference voltage sample to a voltage comparator controlling amplification, a storage capacitor in the display circuit retaining the previous signal sample value during each amplifier calibration cycle.

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Erlangen, Germany

Bernd Kusserow