The invention relates to a device for determining the path of an in particular metallic target, with at least two detection devices so positioned along a path to be monitored that the sensitivity curves of immediately adjacent detection devices at least partly overlap, the detection devices in each case having at least one inductance coil and at least one oscillator and as a function of a damping of the oscillator by the target supply a distance signal, with at least one converting device operatively connected to the detection devices for converting the dampings detected by the detection devices into analog signals, particularly current and/or voltage signals, and with at least one evaluating device operatively connected to the converting device or devices for determining and reading out a local position of the target from the analog signals going back to the detection devices.

A magnetostrictive wire control rod position detector assembly which will allow nuclear reactor output to be increased, control performance to be improved, and peripheral equipment to be rationalized by continuously and accurately detecting the position of a control rod in a reactor core is provided. A magnetostrictive wire control rod position detector assembly (20) comprises: a magnet or magnets (21) mounted on a non-magnetic portion of a movable member (3) which is free to move in the longitudinal direction on the inside of a cylindrical member (1) and is partly composed of a non-magnetic material; a magnetostrictive wire detector (22) longitudinally mounted on the outer circumference of said cylindrical member, which is provided with a receiver (26); and a pulsed current generator circuit (37) which supplies a pulsed current from the receiver end to the magnetostrictive wire of the magnetostrictive wire detector. When the magnetic field generated in the magnetostrictive wire by the pulsed current approaches the magnetic field of the magnet or magnets on the movable member, mutual interference between the magnetic fields generates torsional waves in the magnetostrictive wire, and the physical position of the movable member can be accurately measured if the propagation time of the torsional waves is measured by the receiver.

A noncontact distance measuring system with a sensor (2) that draws on alternating current and has a measuring coil (1), an electronic supply/evaluation circuit (3) connected with the sensor (2), and an electrically and/or magnetically conductive test object (4) associated to the sensor (2), the measuring coil being packaged in a preferably cylindrical housing, and the test object (4) at least partially surrounding the coil housing (5) and being movable in its longitudinal direction, is structured so as to reduce the overall length and to avoid the output impedance of the measuring coil from the position of the test object, in that the test object (4) is designed as a ring (6) surrounding the coil housing (5) at a distance, that the measuring coil (1) has at least two voltage taps (7), so that depending on the number of voltage taps (7) either voltage values can be tapped sequentially between the individual voltage taps (7) and a reference potential (8), and that the electronic supply/evaluation circuit (3) includes an electronic component (10) for adding up the tapped voltage values to a total voltage correlating with the position of the test object (4), or individual voltages between the voltage taps (7) can be tapped sequentially, and that the electronic supply/evaluation circuit (3) includes an electronic component (9) for adding up the tapped individual voltages to increasing voltage values and a further electronic component (10) for once again adding up the voltage values to a total voltage correlating with the position of the test object.

Coils placed at spaced locations along the path of an axially movable magnetically permeable and/or electrically conductive rod, which changes the impedance of each coil as it passes through, are connected in sets with each set comprising two series connected groups of equal numbers of parallel connected, non-adjacent coils energized by an a-c source. The voltage at the common node of each set of coils, which fluctuates as equal and unequal numbers of coils in the two groups in a given set are penetrated by the end of the rod, is compared with the voltage at the common node of a pair of series connected resistors, also energized by the a-c source, to generate one digit of an unambiguous, multi-digit, digital rod position signal. Since only one signal wire to the remote electronics is required for each set of coils, and since they only carry a voltage signal, the required wiring is minimized. Compensation is provided to maintain the location of the rod end relative to each coil at which the digital signal changes state despite variations in temperature and voltage.

The rod position indicator system of a pressurized nuclear reactor can be calibrated for one or more control rods without shutdown of the reactor. The procedure involves lowering reactor power to a level at which the control rod which appears to be misaligned can be fully inserted and its rod position indicator calibrated.