SU1059425A1 - Device for measuring small tilt angle - Google Patents

Abstract

A DEVICE FOR MEASURING SMALL TILT ANGLES, content is a differential capacitive sensor whose capacitor cores are formed by two adjacent arms of a bridge measuring circuit, a generator, an amplifier, whose input is connected to a capacitor of a differential capacitive sensor, a phase-sensitive detector, one of the inputs of which is connected to a generator, and the second is with an amplifier output, and a low-pass filter, which is connected to the output of a phase-sensitive detector, so as to improve the accuracy and increasing the distance measurement: it is equipped with an inductively coupled transformer and commator of the number of turns, the transformer primary winding is connected to the generator, the ends of the first secondary winding having a branch from the middle are connected to the extreme electrodes of the differential capacitive sensor, the second secondary winding with i (L controlled number of turns and one third of the secondary winding with a constant number of turns connected to each other and opposite and connected between the ground and the middle of the first secondary winding, and the output of the low pass filter is coupled to the switch of the number of turns;

Description

The invention relates to a measurement technique, in particular, to devices for measuring tilt angles of a lens.

Device 1 for measuring the angle of inclination is known, comprising a differential capacitive sensor, an alternating current source, an amplifier, an amplitude phase detector and an indicating device. A bubble level with electrodes 1 inserted inside is used as a differential capacitive sensor.

However, this makes it difficult to obtain a linear measurement characteristic and, in addition, reduces the manufacturability of the device.

The drawbacks of the device are also small distance and low accuracy of measurements due to the influence of parasitic capacitors, in particular; capacity, connecting cables between the capacitive sensor and the rest of the device.

Electronic tiltmeters are known which also use bubble levels fzj,

However, the remoteness of this Tiltmeter is achieved by placing part of the measuring circuit in the sensor body, which increases its size and limits the scope of application of the device.

Nn1 closer to the invention in its technical essence and the achieved result is a device for measuring small deviations from the horizontal, which contains a differential capacitive sensor, a generator that supplies a bridge measuring circuit, to the output of which is connected in series with a large input. resistance, differential amplifier, phase-sensitive detector (synchronous demodulator), the second input of which is connected to the output. generator, and a low-pass filter. As the sensor, a vessel is used that is partially filled with a conductive liquid, such as mercury, above which two flat electrodes are placed. Two capacitors of the differential capacitive sensor, each of which is formed by a flat electrode and a free surface of a conductive fluid, respectively, are a common electrode, form two adjacent arms of a bridge measuring circuit. Two other adjacent arms are formed by two exemplary capacitors h.

The disadvantages of the known device are low accuracy and limited measurement distance due to the use of an unbalanced bridge circuit, due to which the voltage instability of the power supply generator and the instability of the input impedance of the amplifier influence the readings; influence on the parasitic capacitive readings

connections, including the own capacitance of the connecting wires between the sensor and the measuring circuit; the conversion function of the device, which is a capacitance ratio, sensor capacitors, the non-linearity of which begins to be felt when measuring angles of the order of one

CORNERS WITH € (KUND,

The aim of the invention is to improve the accuracy and increase the distance of the measurement.

The goal is achieved by the fact that a device for measuring small tilt angles, containing a differential capacitive sensor,

two capacitors of which form two adjacent arms of a bridge measuring circuit, a generator, an amplifier, whose input is connected to a common electrode of a differential capacitive sensor, is a phage-sensitive

a detector, one of the inputs of which is connected to a generator, and the second with an amplifier output, and a low-pass filter, which is connected to the output of a phase-sensitive detector,

0 additionally introduced a transformer with inductive coupling and a switch of the number of turns, with the primary winding of the transformer connected to the J gene {ator, the ends of the first secondary

5 windings, having a tap from the middle, are connected to the extreme electrodes of the co-capacitors of the differential capacitive sensor, the second secondary winding with an adjustable number of turns

Q and a third secondary winding with a constant number of turns are connected in series and counter and are connected between the middle of the first secondary winding, and the output of the low-pass filter is connected to the switch 1m

the number of turns.

The drawing shows a block diagram of the proposed device.

The device contains a generator 1, the output of which is connected to the primary winding 2 of transformer 3 by close inductive coupling. Two equal sections 4 and 5 of the first secondary winding are connected to two flat electrodes of the capacitors of the differential capacitive sensor 7 at their extreme ends, and the common electrode 8 of capacitors, the role of which is performed by the free surface of the conducting fluid is connected to the inlet

0 amplifier 9. The output of amplifier 9 is connected to one of the inputs of the phase-sensitive detector 10, the second input of which is connected to the power supply 1, and the output to the input of the filter 11 of the lowest 5 frequencies. The switch 12 of the number of turns is connected to the second secondary side 13 of the transformer 3 so that when the positive or negative voltage from the output of the low-pass filter 11 is applied to the input of the switch 12, the number of turns of the winding 13 changes, respectively, upwards or downwards. the input of the zero-voltage switch 12, the regulation of the number of threads in the winding 13 is stopped and the number of turns collected is retained Hells manna. As a switch rj -1.2: a strong engine from switches, a reversing pulse counter With a clock generator and a set of keys, etc., can be used, for example, The position of the switch 12, which uniquely corresponds to the dialed number of turns of the winding 13, is the output parameter of the device. Consistently with the second regulated secondary winding 13 of transformer 3, a third winding winding 14 is turned on, having a constant number of turns less (for example, twice) than the maximum number of turns of the adjustable winding 13. Windings 13 and. 14 included counter. By adjusting the number of windings of 13 ss, the flashing voltage of windings 13 and 14 can be inverted in phase, passing through zero at a certain position of the switch 12. This provides a level; Sewing the device when measuring tilts both in one and the other side from the horizontal position The device operates in the following way. Suppose that the numbers of turns, windings 13 and 14 are equal in the initial state of the device. The output voltage of the generator 1 is supplied to the primary winding 2 of transformer 3. The resulting outputs of sections 4 and 5 of the first secondary winding of transformer 3 for equal-in amplitude and phase-opposite voltages are applied to the flat electrodes 5 of the capacitors of sensor 6. If there is no the capacitance slope of the capacitors are equal, and the signal taken from the common electrode 7 of the capacitors is zero. When the sensor 7 is tilted, the capacitance C (and MF of the capacitors change, and /. ES g eS | Gx a: 7 where the dielectric constant of the gas in the gap of the capacitors (for air) S is the area of the flat electrode o is the initial gap of capacitors C, and. GI, X is the increment of the gap due to the slope (for small tilt angles, the displacement of the capacitor electrodes can be considered plane-parallel.) After being amplified by amplifier 9, the difference signal goes to the phase-sensitive detector 10, a constant signal from the output of which is filtered by low-pass filter 11, from (in particular, serves to attenuate the influence of the oscillations of the surface of the liquid 8 of the sensor 7; The voltage of one or another polarity from the output of the low-pass filter 11 affects the switch-12 of the number of turns, which changes in one direction or another the number of turns of the winding 13, In the middle of the first secondary winding of the transformer 3, the junction point of sections 4 and 5 | is supplied with voltage iU connected in series and opposite: bypass 13 and 14 i 3 of the voltage from the phase of this voltage, it is added or subtracted from section 4 and 5 first Tues The normal winding of the transformer 3, and always the voltage increase on one flat sensor electrode corresponds to the same voltage reduction on the other, and vice versa. The number of turns is controlled by the switch until the mismatch signal of the bridge circuit is zero, t, e. until the bridge circuit comes to a state of equilibrium, the condition of which is expressed by the following formula; (,, (2) where and is the voltage taken from half (from section 4 or from section 5) of the first secondary winding of the transformer 3. Substituting values C and C, from (C into equilibrium condition (2) and denoting t , (3) we obtain an extrinsic ,,.. (4) The XI value can also be determined from the expression: where t is the distance between the centers of the flat electrodes, L is the angle of inclination. For small angles of inclination ig ci can be replaced by , then xDl. (6) Equating the expressions (4) and (b) we get (where K is a constant value, is equal to g / d, it is easy to see from (2) and 3 that the proposed device realizes This achieves a much better linearity of the overall performance of the proposed device, compared with the known angle of hundreds of angular seconds when measuring tilt angles. Thus, the measured tilting angle ei is directly proportional to the value of f f which is determined by the ratio of the difference of winding turns 13 and 14 to the constant number of turns of one of the sections of the first secondary winding. The magnitude of the separation of the number of turns of the adjustable winding 13 and winding 14 with a constant number of turns uniquely corresponds to the output sy nsshu switch 12 the number of turns. Since the voltage of the supplying generator is not included in the final expression (7), the instability of its amplitude will not affect the measurement result. Due to the close inductive coupling of the transformer windings, the ratio of the voltages, supplying Nbix to flat electrodes, 6 differential capacitive sensor 7, is kept almost constant, while eliminating the influence of parasitic capacitances of connecting cables. In the equilibrium state, the signal at the output of the bridge circuit is zero, therefore the capacitance of the connecting between the sensor and the amplifier and the input resistance of the amplifier do not affect the measurement result. Thus, the accuracy of the measurement of the angle of inclination increases, the distance increases (the sensor can be located at a distance of several tens of meters from the measuring circuit /. and prototype, since it significantly improves the accuracy and distance of measurements. The wounding of the task of accurately measuring small angles of inclination / is very important for geodesy, astronomy, and other branches of the national economy. The use of a technologically simple compact sensor, the increased distance of measurement, as well as digital reception of the signal make it possible to use the device in automatic control systems for multipoint monitoring of the position of objects. At present, for measuring small angles of inclination Bubble levels. The electronic level EU-2, created at the Institute of High Energy Physics of the GKAE USSR, was adopted as the base device. When measuring small angles (up to 50 angular seconds), with the length of connecting cables (with a running capacity of 100pores / m 25-30 m and changing the value of the total capacitances of the supply cables in the arms of the bridge measuring circuit (due to temperature changes and t, n, 1, by 5-10%, the error of angle measurement by the proposed device does not exceed 0.3-0.5%, while the error of angle measurement by the base device (ceteris paribus conditions) can reach 10%,

Claims (1)

DEVICE FOR MEASURING SMALL TILT ANGLES, containing a differential capacitive sensor, two capacitors of which form two adjacent arms of the bridge measuring circuit, a generator, an amplifier, the input of which is connected to a common electrode of the capacitors of the differential capacitive sensor, a phase-sensitive detector, one of the inputs of which is connected to the generator and the second - with the amplifier output, and a low-pass filter, which is connected to the output of the phaeo-sensitive detector, characterized in that, with the aim of increasing accuracy, cheniya listaniioniosti of _z measurements were, it is provided with a transformer with inductive coupling and switch the number of turns, the primary winding of the transformer is connected to the generator, the ends of the first secondary winding having a center tapped, / are connected to the extreme electrodes of the differential capacitive sensor, a second secondary winding with variable number turns and the third secondary winding with a constant number of turns are connected sequentially and counterclockwise and connected between the ground and the middle of the first secondary winding, and the filter output is lower pilots at coils connected to the switch number. next to last>