DE3545257C2 - Sensor for measuring electromagnetic pulses - Google Patents

Description

The invention relates to a sensor according to the preamble of claim 1, as derived from the book "Nuclear Electromagnetic Puls ", Expert Verlag, vol. 110, electrical engineering, July 1985, p. 219 is known and described below becomes.

EMP sensors from various manufacturers are known the principle of sensor and measuring cable transmission, or sensor with fiber optic transmission.

In the "sensor with measuring cable" solution shown in FIG. 1, as is known from company brochures, the measuring cable must be routed as far as possible on equipotential lines of the field strength in order to avoid measurement errors. This usually fails with complicated measurement objects. The measuring cable also causes field distortions.

For EMP measurement with fiber optic transmission, Fig. 2, also known from company brochures, in addition to the sensor, a shielded housing is usually required to accommodate extensive, expensive electronics and a battery. The latter has a short lifespan. But the electronics housing also interferes with the field to be measured, since it is the same size and is placed in the immediate vicinity of the sensor.

In Proceedings of the 18 ^th International Conference on Lightning Protection, p 79ff, Munich in 1985 to house the measuring electronics is proposed in a ball field probe, see. Fig. 3. The disadvantage of field distortion does not apply here. Disadvantages are expensive electronics and limited battery life.

Fig. 4 shows a solution according to the document cited at the beginning, in which a laser light beam hits a Pockels cell PZ via a polarizer and a precisely applied lens. Metallic measuring electrodes are flanged onto the cell as coupling antennas. The laser light is modulated in terms of its polarization to the extent of the EMP measuring pulse. If a lens and a polarizer are also attached to the opposite side of the Pockels cell, the field pulse can be guided and evaluated via a fiber optic cable to a fiber optic receiver. Disadvantages of this arrangement are a transmission frequency range which is limited downward at 10 kHz and upward at 100 MHz, and a complicated, sensitive coupling of the optical fiber to the Pockels cell PZ.

Furthermore, from Baum, C.E .; BREEN, E. L .; GILES, J. C .; O′NEILL, J .; SOWER, G., D .: "Sensors for Electromagnetic Pulse Measurements Both Inside and Away from Nuclear Source Regions "; in: IEEE Transactions on Antennas and Propagation, January 1978, No. 1, Pages 22 to 35 a sensor for measuring electromagnetic pulses with a body sensitive to electromagnetic fields, are realized on the coupling antennas by means of which EMP measurements be carried out, the measurement signals via a line are transmitted to an evaluation unit. A disadvantage of this The solution is that the lines interfere with the measuring field becomes.

Furthermore, from DE 35 04 945 A1 an arrangement for measuring the electrical Voltage parameters of a high voltage conductor are known. In this measuring arrangement is a piezoelectric for the conversion of measured values Realized crystal that mirrors on one of its end faces is.

This mirrored surface is illuminated at an acute angle, whereby the light beam reflected on the mirror surface over the medium Air collected in a receiving and evaluation unit and regarding its deflection is evaluated. You can use the Transmission medium air Interference signals in the form of extraneous light are coupled in or due to inhomogeneities in the air, useful signal changes occur, which requires additional compensation measures become.

Furthermore, from US 43 19 186 is the formation of an optical Known transmission path, consisting of a piezo element bordering optical fiber, at one end a laser and at the other end of which is a photodiode. Will that now Piezo element excited to deform by external influences, so the optical fiber is clamped, which leads to a modulation of the Laser light leads.  

Furthermore, a fiber optic measuring device is known from EP 10 221 A1, in which a planar capacitor with one-sided mirrored and movable Capacitor plate is realized. The mirrored and movable The capacitor plate is illuminated via an optical waveguide. The mirrored and movable capacitor plate is located retired, the light of the optical fiber hits on the mirrored and movable capacitor plate and is then reflected back into the optical fiber. Here is to achieve sufficient measuring accuracy of the capacitor encapsulate and through further measures against environmental influences, which e.g. B. can occur in the form of mechanical vibrations decouple.

Furthermore, from DE 32 30 159 C1 a piezoelectrically excitable Cube corner reflector known, in which mirrored in a triple mirror Piezo elements are arranged that have an electrical Modulator can be deflected so that incident in the triple mirror Light can be modulated. This is a general Showing the way to modulate light and to reflect parallel with little scatter.

The object of the invention is to provide a simple sensor Measurement of electromagnetic pulses of the type mentioned at the beginning to realize the impulsive field strengths of the Electro Magnetic Pulse (EMP)

• - measures with sufficient accuracy,
• - is passive, i.e. works without an active power source,
• - The field to be measured as little as possible disturbing his presence,
• - has little expenditure on electronics,
• - The measuring signals without disturbing the measuring field itself (e.g. via supply lines) to the measuring point without interference transmits.

The solution to this problem can be found in claim 1 according to the invention. The further claims contain advantageous ones Embodiments of the invention.

The invention is explained in more detail below with reference to FIGS. 5 and 6. Fig. 5 shows a sensor according to the invention in the measuring arrangement.

A piezoelectric crystal PW is placed on one of its Side surfaces designed as a mirror surface. On the mirror surface a directed beam of light hits from a Light source LQ, e.g. B. a laser beam. About the flanged metallic measuring electrodes are attached to the Piezo crystal PW in the case of the EMP measuring pulse voltage pulses placed the mechanical dimensions of the Enlarge the crystal in time with the pulse voltage or downsize.  

The EMP sensor according to the invention with a piezo transducer or piezoelectric crystal PW is fixed in the field, for. B. with dielectric brackets, installed and illuminated by a fixed light source LQ from a small angle ϕ. The measuring pulse is shown on a calibrated measuring plane ME based on the light beam deflection. The measuring plane ME is preferably arranged so that the reflected light beam strikes it perpendicularly in the idle state. The wavelength λ of the light beam should be approximately ten times greater than the roughness depth of the mirror surface, cf. Fig. 6.

For recording the measured electromagnetic pulses a rotating drum can be arranged in the measuring plane be, whose light-sensitive surface with the reflected Laser beam is described. The axis of rotation is to be arranged parallel to the deflection of the laser beam, so that the written pulse is temporally resolved becomes.

In another embodiment, the measuring level consists of a CCD display bar. This is with a very fast clock frequency scanned with regard to the deflection of the laser beam. The charge values are a function of the amplitude stored and processed over time.

The advantages of the sensor according to the invention are:

• - no measuring line to the sensor
• - No measuring electronics in the sensor or in its vicinity
• - no battery, because passive
• - interference-free transmission of measured values
• - very simple and economical solution  
• - Attachment of E, D, H and B field electrodes of any kind one- or three-dimensional configuration possible
• - very small sensor, resulting in little field interference, high sensitivity.

Claims (6)

1. Sensor for measuring electromagnetic pulses, with a body sensitive to electromagnetic fields, on which coupling antennas are flanged, and a light source, the light of which is focused on the body, characterized by the following features:

• - The body is a piezoelectric crystal (PW), one side surface is designed as a mirror surface;
• - The mirror surface is illuminated by a light beam from the light source (LQ) at an acute angle (ϕ);
• - The light beam reflected on the mirror surface is collected on a calibrated measuring plane (ME) and evaluated with regard to its lateral deflection;
• - The wavelength λ of the light source (LQ) is chosen about ten times larger than the roughness depth of the mirror surface.

2. Sensor according to claim 1, characterized in that the light source is a laser. 3. Sensor according to claim 1, characterized in that the light beam at rest perpendicular to the measuring plane (ME) hits. 4. Sensor according to claim 1, characterized in that the crystal (PW) is fixed using dielectric mounts is installed in the field to be measured. 5. Sensor according to claim 1, characterized in that in the measuring plane a rotating drum with photosensitive Surface is arranged. 6. Sensor according to claim 1, characterized in that the Measurement level consists of a CCD display bar.