Semiconductor measuring transducers of deformation, temperature and magnetic-field for application in the conditions of radiation irradiation, wide range of temperatures and magnetic fields
V.A Belyakov, N.T.Gorbachuk, P.A.Didenko, E.A. Lamzin, etc. Semiconductor measuring converters of deformation, temperature and magnetic field for application in conditions of a radiating irradiation, wide range of temperatures and magnetic fields. Questions of the nuclear science and technics. A series: the electrophysical equipment. 3 (29), 2005. St. Petersburg, Russia.
Semiconductor materials possess a high sensitiveness to different external influences and at development on their basis of measuring transducers (sensors) of physical sizes /15/ aim to use such materials and construction of pickoff, that a transducer maximally reacted on a measureable parameter and scorned small on other. In connection with development of criogenics technique, atomic energy demand grows on transducers are capable of working in the range of temperatures from climatic to cryogenics, magnetic fields to 10 Òë and possessing radiation stability /1,4/.
In modern sensors of creation semiconductor material is used as a rule in a pellicle kind, advantages of which consist in possibilities of the use of integral technologies, creations of cerouss of transducers with identical descriptions, more subzero cost of the got pickoffs of and other
By us for creation of measuring transducers tapes of gaas are used on a semiinsulating gaas, tapes of polisilicon on linings from silicon, tapes of germanium on linings from a gaas, and also by volume dispersible germanium. Researches are conducted in the range of temperatures 4.2-400 Ê.
1. Measuring transducers of mechanical deformations
At measuring of mechanical deformations by means of single strain gauge in the wide range of temperatures, in the conditions of the difficultly tense states of object, in presence the magnetic fields, exactness of measuring considerably goes /down 2,3/. New possibilities in the increase of exactness of measuring are opened by the use of tapes on insulating bases, when a pickoff is formed as a certain microcircuit of crystallgraphicly by oriented, and the construction of transducers allows to remove transversal strainsensetivity /4,5/.
For creation of measuring transducers of mechanical deformation tapes of poly silicon n and ð-type of conductivity are used, in thick 0.6 mkm and alloying levels a 10^17 - 5·10^19 cm^ - 3 . the Alloying admixture the coniferous forest served as for p -silicon.
On a fig. 1 the schematic image of transducers of deformation and polarity of connecting of feed and measuring devices is shown. He consists of integral pickoff 1, silicon executed on the basis of tape, besieged on lining 2 from single-crystal silicon with the layer of oxide on a surface. Electric conclusions 3 made from the aluminium wire of d=80mkm, the ends of which are provided with the strips of metal, solderable by an ordinary solder. A construction and integral execution of pickoff of sensor provide òåðìî thermo indemnification of basic parameters, indemnification of influence of magnetic-field and absence of transversal tenzo sensitiveness. Size of base of sensor of 8ìì, entrance and output electric resistances depending on the level of alloying and thickness of tapes 200 -3000 Ohm, the current of feed depends on the size of resistance and as a rule is within the limits of 1 -10mA. Distinction in the sizes of electric resistance of sensors to one party does not exceed 5%, and if necessary party of sensors can be formed from practically identical on technical descriptions. Tenzo sensitiveness at tension of feed of 5Â approximately 100mkV/mln^- 1. Size of a zero (initial) output signal of sensor of Uî ~ 20mV and if necessary maybe to be driven in by near to the zero. Temperature dependence of the strain sensitiveness no more than 0,02%, and Uî ~ 20mkV/Ê. Descriptions of basic types of transducers of deformation of resulted in the table of I.
Principle of work of strain gauge consists in the change of electric resistance of capacitance-resistance elements of integral microcircuit at the appendix of mechanical deformation along the axis of sensor, to the loss of indemnification microcircuits and appearance, as a result of it, electric tension of Uâ on measuring contacts at the feed of sensor a current or tension ( fig. 1). Preliminary graduate a sensor i.e. getting dependence of output tension of Uâ of size of mechanical deformation of e in future on the size of output tension of sensor, hardly envisaged on an object, determine deformation of object.
Measuring at a stationary temperature is considerably simpler, than in the conditions of changing temperature. At a stationary temperature the change of output signal of Uâ of strain gauge depends only on the size of deformation along the axis of sensor and size of current or tension of feed (Iï, Uï), maximally possible sizes of which specified in the passport of sensor. The maximally legitimate values of Iï or Uï get out from the condition of unachievement of heating of sensor at which his testimonies begin to depend on nascent instability of temperature or the energy dispersed on a sensor changes the terms of heat exchange in the point of measuring. The sizes of Iï and Uï if necessary can be diminished as compared to passport values. Thus all other technical descriptions diminish proportionally. The choice of chart of feed (Iï or Uï) of fundamental value does not have, but can insignificantly tell on temperature dependence of sensitiveness and zero (initial) output signal. The size of deformation at measuring in the conditions of termostability is determined on a formula:
ε = (Uâ - Uî)/k (1)
where Uâ is an output signal of sensor after appearance of deformation of e investigated object, Uî is an initial output signal which after editing of sensor on an object can insignificantly differ from indicated in a passport, as in a passport Uî is indicated for free strain gauge, k =ΔUâ /Δε - strain sensitiveness sensor.
For editing of sensor on the object of research can be used widely applied in strain measures glues of ÁÔ- 2, BC - 350 et al, providing sufficient inflexibility of editing. Admission of the use of this connective material can be tested on the size of creep of testimonies of sensor after the ladening of test beam which must not exceed the permissible error of measuring.
Measuring at an unstable temperature become complicated that here due to the difference of coefficients of thermal expansion of materials of strain gage and object measuring, there are additional thermal tensions and deformations in glued on strain gauge. It causes the change of a zero output signal of sensor, measured in the free state. In an order to be delivered from influence of termotensions of sensor on exactness of measuring, next to a measuring (by a worker) sensor the identical sensor of comparison is set glued on a free plate, made from material of object of measuring. Thus for the receipt of size of measureable deformation it is necessary to take advantage of formula
ε = [(Uâ - Uî) - (Uâ1 - Uî1)] / k
where Uâ and Uî - accordingly the measured and zero weekend signals of working sensor at this temperature of Ò, Uâ1 and Uî1 ñîîâåòcòâåííî the measured and zero weekend signals of sensor of comparison at this temperature of Ò, k - strain sensitivity at this temperature. If zero output signals of working sensor and sensor of comparison differ insignificantly, then the above-mentioned formula is simplified:
ε = (Uâ - Uâ1)/k
At determination of coefficient the tenzo sensitiveness sign of deformation of compression is accepted by negative and it is taken into account in passport data on a sensor.