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2. Measuring transducers of temperature
For taking temperature in a wide range the different constructions of sensors and different semiconductor materials are used as basis for a pickoff on purpose to create thermo-resistors with high stability and small subject to influence of extraneous external influences /7,8/.
By us for creation of measuring transformers of temperature the by volume dispersible germanium and also tapes of germanium got on the worked out technology is used.
A dispersible germanium is got on the basis of initial germanium of n -типа with specific resistance 15 Ohm·of cm by influence of high pressures and temperatures. As a result a dispersible germanium had a р-тип of conductivity with the high concentration of transmitters of current at a room temperature, that allows to suppose that acceptor levels are created by structural defects /6/.
On a fig. 6 the schematic image of transformer of temperature of pellicle germanium is shown. Sizes of pickoffs of transducers from the by volume germanium of 0.5х1.0х1.0 mm, pellicle 0.2х1.0х1. 0 mm. Electric resistance at 300 K makes a size 1-10 Ohm, at 4.2 K approximately 50-100 kOhm. Sensitiveness at 4.2 K - 100-200 %/К. Currents of feed at 4.2 K - 1-10 mkA. Pellicle transducers have electric resistance at 300 K 1-50 kOhm and intended, mainly, for measuring in a climatic range. An insulating base can be metal-backer, that assumes application of soldering at editing and provides a good thermal contact. Descriptions over of basic types of transducers of temperature are brought in a table 3.
On a fig. 7 characteristic temperature dependence of size of electric resistance of sensors is shown, on the basis of dispersible germanium, and on a fig. 8 dependence of size of error of taking temperature, arising up in the magnetic field due to the effect of magnetoresistance .
For taking temperature in the magnetic fields by us the construction of pickoff, allowing to compensate influence of magnetic-field by addition on the measuring contacts of effects of Hall and magnetoresistance /9/. At measuring of effect of Hall measuring contacts place symmetric opposite each other, is similarly worked out, athwart by a current, and at measuring ofmagnetoresistance they are displaced or are together with the last.
If to place current and measuring contacts on a standard how it is shown on a fig. 9, then at the directions of current and magnetic-field indicated on a picture, in the semiconductor of n - type conductivity change of tension on the measuring contacts of Uu, related to the effect of Hall and change of tension, related to the increase of resistance of standard in the magnetic field, will have different signs, and, folded, will result in the less size of measureable tension of Uu as compared to that which would be at the exception of one of effects. In case if Hall tension on contacts will be equal to the change of tension on the same contacts due to magnetoresistance , then measureable tension of Uu will be such, as well as in absence the field and to correspond calibration, temperature-dependent only. We are show /9/, that for this purpose measuring contacts must be placed in the distance:
L = aRx /ρM
where and is a width of plate, Rx and M =Δρ/ρB - permanent Hall and magnetoresistance accordingly in area of taken temperature, ρ is specific resistance, B is induction of magnetic-field.
Exactness of measuring such sensor depends on exactness of observance of parameters of construction of sensor and degree of linearness of dependences of effects of Hall and magnetoresistance from magnetic-field. On the sensors made by us on the basis of tapes of germanium on a gaas exactness in area of temperatures of liquid helium and magnetic fields to 8 Тл not worse 0.01 К.
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CONVERTERS, GAUGES, SENSORS
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