SE410521B - METGIVARE WITH OPTICAL FIBER - Google Patents

Description

15 20 25 30 35 7801965 -0 the sensor's measuring range and accuracy can be adapted for different application areas.

The use of optical fibers also has other advantages. The sensor becomes insensitive to erek fi neka oçh Navman fan. one gets galvanic ieoiation manen sensor and unit of measurement. The sensor can be used in an explosive environment without any special safety arrangements. There are no possibilities for sparking or short-circuiting. The fiber of the measuring sensor constitutes a closed system. Dirt and other contaminants can not affect. the measurement result.

What otherwise characterizes the invention is stated in the claims.

The invention will be explained with the aid of the accompanying drawing figures.

Fig. 1 shows the principle of the invention.

Fig. 2 shows the amplitude and wavelength of the curvature. in Fig. 3 shows the relationship between attenuation and amplitude for a certain fiber at different mechanical wavelengths' in * i -m- * In Fig. 4; shows a simple design of a deformation zone. K Figs. 5, 6 and 7 show a sensor with an increased number of deformation zones.

Fig. 8 'shows a direction-independent deformation sensor.

Fig. 9. shows. a sensor with a swivel yoke.

Fig. 10 shows the sensor with temperature compensation.

Figures 11 and 12 show temperature sensors.

Fig. 13 shows an alternative arrangement of transmitter and receiver.

Fig. 1 »shows the principle of a power sensor according to the invention. If a radiation source 1, for example a laser transmitter, emits light through optical fiber 2 of multimode type or single mode type and preferably consisting of a core surrounded by a sheath. A detector 5 is arranged to receive and detect the light radiation which has passed through the core of the fiber. A device for deforming the fiber generally consists of two. parts 4 and 5 between which the fiber passes. The two parts are formed with their respective corrugated surface 6, 7, which face each other and preferably so that the wave peaks of one part lie opposite the wave parts of the other part. When the two parts 4 and 5 are pressed against each other with a force F, the fiber will bend. The curvature has a wavelength / L, which is equal to the distance between two wave peaks and the amplitude x of the curvature depends on. the mutual position of the two parts. wavelength and amplitude are shown in Fig. 2. Fig. 5 shows the relationship prevailing in a certain fiber between the attenuation eC and the amplitude x at different mechanical ones. wavelengths. Curvonza for wavelength indicates from left to right increasing wavelengths. Fig. 4 shows a deformation device, in which the fiber 2 passes only once through the device. Fig. 5 shows that the fiber passes the deformation device several times. It can then be wound wound around one of them. part a number of turns. Fig. 6 shows that the fiber is wound back and forth in loops. In the embodiment according to Fig. 7, the part 4 is designed as a frame, which encloses the second part 5. The fiber 2 can here advantageously be wound around the part 5 a number of turns.

Thereby a longer deformed zone of the fiber is obtained, which gives the sensor greater sensitivity. Fig. 8 shows the design of a sensor which is independent of the direction of the actuating force. The outer part 4 is designed as a cylindrical ring with a wavy inner surface, while the part 5 is designed as a cylinder with a wavy outer surface. and placed inside the part 4. The fiber 2 is wound a number of turns around the inner part S. If the outer part is made elastic, the sensor can be used for measuring versatile pressure.

Fig. 9 shows a sensor with two. independent devices for deforming fibers. The transmitter 1 emits radiation through two different fibers 2a and 2b and each fiber passes its own deformation device with the parts 49., Sa respectively 4b, 5b. each fiber has its own detector ša resp šb. The output cells from the detectors go to a summing device 6, which determines the difference between the signals. A U-shaped yoke 7 has the web 8 mounted in a shaft 9 at the center of the web and flange edges 10a and 10b, respectively, abutting each of the deformation sensors. If the force F acts downwards on. the flange 10a will have an equal force acting upwards on. flange 10b. The left fiber 2a will thus be subjected to a considerably larger deformation than the right fiber 2b, which means that the signal from the detector yes. becomes smaller the signal from šb.

Fig. 10 shows a sensor with temperature compensation. A block 11, which is subjected to the force to be measured, contains a deformation device 12a for the fiber 2a and a second deformation device 12b for the fiber 2b. The device 12a is oriented so that it can be actuated by the force F, while the second deformation device 12b is rotated 90 ° and is thus substantially unaffected by the force F. When the force F = 0, the output cells from the two detector arms Ba and Bb be equal. In the transmitter 6, the difference between the two signals is determined.

The output of the summing device thus becomes temperature-independent.

Fig. 11 shows a temperature sensing sensor. The two parts 4 and 5 are connected to each other at their ends by means of connecting elements 15 of a material with a high coefficient of temperature expansion. If the elements 13 have a positive temperature coefficient, the fiber is given a certain bias, which decreases with increasing temperature as the elements 15 increase in length. Fig. 12 shows another temperature sensor, in which

Claims (3)

,. The two parts 4 and 5 have a high temperature coefficient and are surrounded by a frame 14 of a material with a low temperature coefficient. with demxa sensors the deformation increases with rising temperature. Fig. -13 shows an alternative arrangement of transmitter and detector, where the transmitter 1 and the detector 5 are arranged next to each other. The light-emitting fiber * 21 from the transmitter and the light-initiating fiber 22 to the detector are connected at a point 23 to each other and to a third fiber 24, which is located between the point 25 and a branch point 25 located in the vicinity of the force-emitting deformation device 4. constitutes the conductor of both the outgoing and the returning radiation. The emitted light signal passes via the fibers 21 and 24 to the branch port 25. The signal is divided here and passes through the deformation device 4, 5 in both directions. The signals are summed again at point 25 and pass via the fiber 24 to the branch 25 and through the fiber 22 to the detector 5. The part of the signal which enters the transmitter 1 is ignored. PATENTICRAV; . Measuring transducer, intended for use in measuring mechanical forces or such physical quantities, which can be converted into mechanical forces, which transducer includes: at least one optical fiber (2), a radiation cone (1) for inputting optical power radiation at one end of the fiber, a detector (5) at the other end of the fiber for determining the attenuation to which the input radiation has been subjected during passage through the fiber, at least one device for deforming at least one section of the fiber and comprising at least two in relative to mutually movable parts (4, 5) between which the fiber is located, characterized in that at least one of said. parts (4, 5) are affected by the force to be measured. i i Measuring transducer according to claim 1, characterized in that the said. the parts are on. their facing sides formed with a corrugated surface. (6, 7) and so arranged relative to each other that the wave crests of one surface are located min; for the other was wave fl alar. a Transducer according to claims 1 and 2, the fiber (2) passes between said corrugated surfaces several times below, characterized in that it is in the deforming device. MENTIONED PUBLICATIONS: