Characteristics of optoelectronic discrete displacement converters with hollow and fiber light guides

Static characteristics of relay optoelectronic discrete displacement transducers with concentrated radiation sources based on hollow fibers.
Let us consider the static characteristics of an ODC with an RS and a hollow light guide during longitudinal movement of the ODC, the physical model of which is presented in Fig. 5 when used to control a discrete liquid level in a tank [6,7,8 ].

Fig.5. ODC based on a hollow fiber for discrete control of the maximum liquid level. 1 – reservoir; 2 – liquid; 3 – tank cover; 4 – radiation source; 5 – radiation receiver; 6 – hollow light guide ; 7 – output wires; 8 – protective glass.

Research and calculation using the formulas Ф _∑ =Ф _pr1 +Ф _neg2 and showed that the graph of changes in the static characteristic Ф ₀ = f (H) has the form shown in Fig. 6, a.

Fig.6. Static characteristic of the ODC ( a ) and its discrete form ( b ) for monitoring the maximum liquid level.

Section A (Fig. 6, a) of the static characteristic was 4·10 ^-3 m, and section B was 6·10 ^-3 m. The sensitivity of the converter based on ODPV is determined from expression (20).

(20)

An analysis of formula (20) shows that to increase the sensitivity of an OPPV based on a hollow fiber, it is necessary to increase D ₀ and decrease x ₀ . Figure 7 shows a two-element design of the OPPV, in which single-element OPPVs are installed at the upper (N_max ) and lower (N_min ) levels of the controlled liquid at the upper and lower ends of the hollow fiber [9,10].
Static characteristics of relay optoelectronic discrete converters with concentrated radiation sources based on optical fibers during longitudinal and transverse movements of the external modulating body.
Figure 7 shows a liquid level control device in the form of a measuring tank 1 (which is used in flow metering and other installations) and a level measuring tube 2 . The first design of the ODC is installed in the top cover 3 of the tank 1 and its input 5 light flux from the II 7 and output 6 fiber light guides are located coaxially and the end of the light guide 6 is located flush with the bottom surface of the cover 3 .
Coaxial arrangement of the ends of the light guides 5 and 6 creates an axisymmetric distribution of the effective illumination of the end of the light guide 6 by the light flux reflected from the reflective surface of the liquid level (for example, at the maximum level H _1max ).
In addition, the output end of the light guide 5 (Fig.7) is slightly moved at a distance x ₀ from the plane of location of the input end of the fiber 6 in order to eliminate the background sound of this end of the light guide 6 and creating the necessary radiation indicatrix between the end of the light guide 5 and reflective surface of the liquid level.
Let's consider the physical model of the ODPV of the first design, in which (Fig.7) the liquid level moves longitudinally along the x coordinate .
In the initial position, the coordinate of movement of the liquid level is x=0 and the liquid touches the ends of the outlet aircraft 6. In this case, the light flux Ф ₀ (x) from the ODC is not reflected and does not reach the input end of the outlet BC 6 .
When the ODC moves longitudinally, the luminous flux Ф ₀ (x) from the supply BC 5 , reflected from the TDC, begins to illuminate the inlet end of the BC 6 .



Fig.7. Optoelectronic liquid level monitoring device based on fiber light guides.
According to the physical model in Fig.8, the illumination surface of the input end of the FLG 6 will increase (Fig. 9), therefore the luminous flux Ф ₀ (x) will also increase. Incident on the radiation receiver 8 with increasing longitudinal displacement along the x coordinate.
The diameter of the illuminated surface of the end of the FLG 6 will be: