Results over of measuring of some descriptions of strain gauge are further brought. On a fig. 2 dependences are shown on the temperature of electric resistance (1), zero output signal(2), strain sensitivity k =ΔUâ /Δε (3) and output signal of sensor, glued on a steel plate (4). The last watches thermal tensions.
On a fig. 3 dependence of output tension of Uâ is shown on the size of the attached deformation. A chart testifies to good linearness of description. tensosensitivity of this party of sensors, as be obvious from a chart, 42 mkV/mln^-1 is equal.
Research of error of measuring of deformation is conducted also by means of strain gauge in the conditions when the axis of base of sensor does not coincide with direction of main deformation of object. On a fig. 4 direction of main deformation of e1 beam and layout of sensors chart is shown on a beam. Sensors were fastened by means of glue of ÁÔ- 2. Axis of base of sensor 1 coincides with direction of main deformation of e 1, sensor 2 located under the corner of 30° to e 1, sensor 3 - under the corner of 45° and sensor 4 - under the corner of 90° (coincides with main deformation of e 2). All sensors are taken from one party, made in one technological mode.
The size of the measured deformation of eý is certain with the use of formula (1). Calculation deformations which were used for comparing to got experimentally are certain on formulas, taken from :
εφ = [(ε1 + ε2 ) / 2] + [(ε1 - ε2 ) / 2] cos2 φ
where φ is a corner between direction of ε1 , and direction which deformation settles accounts for. Deformation of ε2 is expected on the formula of ε2 = -- με1 (where m is a coefficient of Puassona). Results over of research are brought in a table 2.
The most difference of εφ from εý is observed for φ =30° and makes a size 6,% that does not exceed the error of experiment. Results testify to practically absent transversal strain sensitivity sensors.
On a fig. 5 results over of one research are brought of sensors in the magnetic field at Т= 4.2 К. Curve (1) corresponds to the size of seeming deformation at affecting of magnetic-field the undeformed sensor (ε =0), and curve (2) on preliminary deformed to ε =1·10^3 млн^-1. the Field of 7 Тl results in an error approximately 3%.
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SENSORS OF PHYSICAL PARAMETERS
•On semiconductor strain gages
Semiconductor strain gages as sensing element a single crystal semiconductor, usually silicon or germanium with a thickness of 20-50 microns, a width of 0.5 mm and a length of 2-12 mm.
The most common technology for manufacturing such elements, — cutting of the single crystal semiconductor followed by etching so that the surface testcustomermap element left of microcracks from machining.
Also a proliferation of so-called dendritic manufacturing technology of strain gages. At the same dendritic tape is produced by extrusion from the melt of the semiconductor, and then break at pre-applied risks. Based on the mentioned technology can produce strain gauges of germanium, silicon, antimonides of gallium and indium, and other materials; the most widely p-editori.
In the late 60's was developed by the strain gages of type "kremnizer" formed of filamentary crystals of silicon.
In the choice of semiconductor strain gages as transducers or sensing elements, consider the following their properties:
- high sensitivity and the possibility of obtaining a large output signal;
the dependence of resistance and sensitivity to temperature;
- limited range of deformation;
- anisotropy of the metrological characteristics.
Anisotropy of properties is primarily manifested in the change of longitudinal and transverse strain. For this reason, in the design of the sensitive elements necessary to ensure coincidence of the axis of symmetry of the single crystal with the direction of the measured strain.