RU2057294C1 - Instrument transducer - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: instrument transducer has AC power supply sources 7 and 8 and several resistors connected in series: first resistor 2, second resistor 11, fifth resistor 2, sixth resistor 10, ninth resistor 1, tenth resistor 9 and third resistor 4, fourth resistor 12, seventh resistor 5, eighth resistor 13, eleventh resistor 6 and twelfth resistor 14. Resistance of firsts resistor 3 depends on the magnitude being measured, while resistance of the remaining resistors does not depend on it. The information on magnitude being measured is carried by phase of summed signal at input of adder 17 read off from signal at input of first comparator 16; with the aid of this comparator, as well as with the aid of second comparator 20, pulse generator 18, AND gate 19, number proportional to phase of summed signal is accumulated in pulse counter 21. This number is memory address in memory 22 where magnitude of value being measured read off indication unit 23 is stored. Control unit 15 is used to control operation of instrument transducer. EFFECT: enhanced efficiency. 5 dwg

Description

 The invention relates to measuring equipment, to devices for measuring quantities, the change of which can be converted into a change in the active or reactive resistance of the elements of the electric circuit.

 A known measuring transducer is a digital thermometer containing a first voltage source connected in series, a resistive converter and a first resistor, a second voltage source connected in series, a second and third resistors, the first and second voltage sources being made in the form of AC voltage sources, and their first outputs and first outputs a resistive converter and a second resistor are connected to a common bus [1] The converter also contains three comparators, two AND elements, a generator and a pulse counter, a decoder and an indication unit. The output of the first comparator is connected to the first input of the And element, the second and third inputs of which are connected respectively to the outputs of the pulse generator and the second comparator, and the output is connected to the counting input of the pulse counter. The third comparator and decoder are designed to control the operation of the And element and the mm pulse counter and constitute a control unit in the community. Two inputs of the control unit are connected to two outputs of the second voltage source, and its first and second outputs are connected respectively to the fourth input of the And element and the zeroing input of the pulse counter.

 Using the known device is carried out phase measurement of temperatures. The change in temperature of the resistive converter is converted into a change in the phase difference between the two electrical signals. One of these signals is observed between the first and second inputs of the first comparator, and the other between the first and second inputs of the second comparator. Using comparators, a pulse generator and an AND element, the phase shift between the signals is converted into the number of pulses accumulated in the pulse counter, proportional to the measured value, which can be read from the display unit.

 A disadvantage of the known device is the low accuracy of the measurements, due to the nonlinearity of the calibration characteristics.

 The closest in technical essence to the proposed one is a digital measuring transducer containing a series-connected first voltage source, first and second resistors, series-connected second voltage source, third and fourth resistors, and voltage sources are made in the form of AC voltage sources, their first outputs and first the outputs of the first and third resistors are connected to a common bus, the resistance of the first resistor depends on the measured value, and the resistance is W The second, third and fourth resistors are independent of it [2] The converter contains the first and second comparators, the outputs of which are connected respectively to the first and second inputs of the And element, the third input of which is connected to the output of the pulse generator, and the output is connected to the counting input of the pulse counter, connected to the storage device. The converter also contains a control unit including a comparator and a decoder. The control unit is connected by input parallel to the first voltage source, and its two outputs are connected respectively to the load input of the pulse counter and to the fourth input of the element I.

 During operation of the converter, the phase of the reference signal observed between the first and second inputs of the first comparator does not change from the measured value, and the phase of the signal observed between the first and second inputs of the second comparator depends on it. In this case, the phase shift between the signals at the inputs of the first and second comparators is converted by them using a pulse generator, an element And, a storage device and a control unit into the number of pulses accumulated in the pulse counter, which is equal to the measured value that is read from the display unit.

The disadvantage of this Converter is the low accuracy of the measurements. This is due to the following reasons. To obtain a sufficiently good measurement sensitivity, it is necessary to choose the angle of the phase shift α between the voltages of the first and second sources, equal to 8-15 ^about . In this case, the phase shift between the signals at the inputs of the first and second comparators, by which the measured value is judged, largely depends on the angle α, and when the latter changes under the influence of various interfering factors, a significant error is introduced into the measurement result. In addition, the nonlinearity of the calibration characteristic introduces an error in the measurement result.

 Another disadvantage of the converter is the narrowness of its functional capabilities, for example, the impossibility of measuring the difference of two quantities, the correction of readings by the value introducing an error, or the impossibility of measuring the value, a change of which can be converted into a change in electric capacitance or inductance.

 The aim of the invention is to improve the accuracy and expansion of the functionality of the device.

 Improving the accuracy of measurements is achieved by the fact that in the measuring transducer containing the first connected voltage source in series, the first and second resistors, the second voltage source connected in series, the third and fourth resistors, the voltage sources being made in the form of AC voltage sources, their first outputs and first outputs the first and third resistors are connected to a common bus, the resistance of the first resistor depends on the measured value, and the resistance of the second, third and four of the resistors does not depend on it, the element And, the first, second and third inputs of which are connected respectively to the outputs of the first comparator, second comparator and pulse generator, and the output is connected to the counting input of the pulse counter, the output of which is connected to the first input of the storage device, and zeroing the input is connected to the first output of the control unit, the second output of which is connected to the fourth input of the And element, and the input is connected in parallel with the first voltage source, and the display unit, the fifth and second ohm resistors connected in series with the first voltage source, seventh and eighth resistors connected in series with the second voltage source, ninth and tenth resistors connected in series with the first voltage source, eleventh and twelfth resistors connected in series with the second voltage source, while the resistances of all additionally introduced resistors are independent of the measured value, the first outputs of the fifth, seventh, ninth and eleventh resistors are connected to a common a bus, an adder, the first and second inputs of which are connected respectively to the common point of the first and second resistors and to the common point of the third and fourth resistors, the third and fourth inputs are connected respectively to the common point of the fifth and sixth resistors and to the common point of the seventh and eighth resistors, and the first and second outputs are connected respectively to the first and second inputs of the second comparator, and the first and second inputs of the first comparator are connected respectively to a common point of the ninth and tenth resistors and to a common point eleventh and twelfth resistors, and the third output of the control unit is connected to the second input of the storage device, the output of which is connected to the input of the display unit.

 The expansion of the functionality of the device is achieved by the fact that part of the resistors of the measuring transducer with a resistance independent of the measured value, or all of them are made so that their resistance depends on the measured or other value of interest.

 The expansion of functionality is also achieved by the fact that part of the resistors or all of them are made in the form of elements of an electrical circuit having purely reactive or mixed (active and reactive) resistances, dependent or independent of the measured or other value of interest.

The introduction of additional resistors and an adder into the measuring transducer makes it possible to obtain a total signal at the output of the latter, and a reference signal at the input of the first comparator and judge the measured value by the phase shift between these signals. Moreover, to obtain a sufficiently good measurement sensitivity, there is no need to choose the angle α equal to 8-15 ^about , as in the prototype, but you can choose it large, for example equal to 60-120 ^about . Then, small changes in the angle α, manifested, for example, in the form of fluctuations that are unavoidable in real devices, will have a much smaller effect on the measurement result, which will ensure a gain in the accuracy of measurements using the proposed measuring transducer compared to the prototype.

 The measurement accuracy is also increased due to the fact that in the proposed device the output of the pulse counter is connected to the input of the display unit not directly, as in the prototype, but via a storage device. This allows you to correct the nonlinearity of the calibration characteristic inherent in phase-measuring transducers, and thereby improve the accuracy of measurements.

 The effect of expanding the functionality of the measuring transducer is manifested, for example, in that it can be used as a liquid flow meter in a pipeline with a constricting device, based on the registration of pressure drops before and after it. For this, for example, the first resistor is made in the form of a reactance (inductance), which depends on pressure, and is placed on one side of the constriction device, the third resistor, made similar to the first, is placed on the other side of the constriction device, and the ninth and twelfth resistors are made dependent temperature to correct the readings of the measurement conversion by the temperature of the liquid, the flow rate of which is measured (since the density of the liquid depends on the temperature, which makes an additional error in measurement).

 In FIG. 1 is a structural diagram of a measuring transducer; in FIG. 2 vector diagram; in FIG. 3 time charts explaining his work; in FIG. 4 block diagram of the control unit; Fig. 5 is a timing chart explaining its operation.

 The measuring transducer contains (Fig. 1) the ninth 1 (R9), fifth 2 (R5), first 3 (R1), third 4 (R3), seventh 5 (R7), eleventh 6 (R11) resistors, first 7 and second 8 voltage sources, tenth 9 (R10), sixth 10 (R6), second 11 (R2), fourth 12 (R4), eighth 13 (R8) and twelfth 14 (R12) resistors, control unit 15, first 16 and second 20 comparators , adder 17, pulse generator 18, element 19, pulse counter 21, memory 22 and an indication unit 23.

 The first 3 and second 11 resistors are connected in series with the first voltage source 7, in series with which the fifth 2 and sixth 10 resistors are connected. The third 4 and fourth 12 resistors are connected in series with the second voltage source 8, in series with which the seventh 5 and eighth 13 resistors are connected. The ninth 1 and tenth 9 resistors are connected in series to the first voltage source 7, and the eleventh 6 and twelfth 14 resistors are connected in series to the second voltage source 8. The first outputs of the first 7 and second 8 voltage sources, ninth 1, fifth 2, first 3, third 4, seventh 5 and eleventh 6 resistors are connected to a common bus (not indicated in Fig. 1). The input control unit 15 is connected in parallel with the first voltage source 7, and its first, second and third outputs are connected respectively to the zeroing input of the pulse counter 21, to the fourth input of the And 19 element and to the second input of the storage device 22. The first and second inputs of the first comparator 16 are connected respectively, with a common point of the ninth 1 and tenth 9 resistors and with a common point of the eleventh 6 and twelfth 14 resistors, and its output is connected to the first input of the element And 19. The first and second inputs of the adder 17 are connected respectively To the common point of the first 3 and second 11 resistors and to the common point of the third 4 and fourth 12 resistors, its third and fourth inputs are connected respectively to the common point of the fifth 2 and sixth 10 resistors and to the common point of the seventh 5 and eighth 13 resistors, and the first and the second outputs are connected respectively to the first and second inputs of the second comparator 20, connected by the output to the second input of the And 19 element, the third input of which is connected to the output of the pulse generator 18, and the output is connected to the counting input of the pulse counter 21. The first input of the storage device 22 is connected to the output of the pulse counter 21, and the output is connected to the input of the display unit 23.

 The measuring transducer is built on the well-known elements of analog and digital microcircuits manufactured by the domestic industry. As elements of an electric circuit with resistances independent of the measured quantity, radio components are used, and with resistances dependent on it or another value of interest, thermistors can be used to measure temperature, inductance to measure displacements, capacitances to measure, for example, humidity, material thickness, liquid level, etc.

 Using an example of the use of a semiconductor thermal resistance (thermistor) as the first resistor 3, the resistance of which depends on the measured value (temperature), the operation of the proposed measuring transducer is as follows.

(фиг. 2), а в результате протекания тока по третьему резистору 4 на нем образуется сигнал А3 (фиг. 3а), которому соответствует вектор

(фиг. 2). Фазы сигналов А1 и А3 не совпадают, а сдвинуты на угол α (фиг. 2) угол фазового сдвига между напряжениями источников 7 и 8. Сигнал А1 изменяется по амплитуде в результате изменения сопротивления первого резистора 3 из-за изменения измеряемой величины. На нижней границе диапазона измерений этому сигналу соответствует вектор

(фиг. 2). Сигнал В1 (фиг. 3а), которому соответствует вектор

(фиг. 2), равный разности сигналов А1 и А3, наблюдается между общей точкой первого 3 и второго 11 резисторов и общей точкой третьего 4 и четвертого 12 резисторов. Сигнал В1 изменяется по амплитуде и по фазе из-за изменения сигнала А1, т.е. в результате изменения измеряемой величины. Этому сигналу на нижней границе диапазона измерений соответствует вектор BI_н(фиг. 2). Аналогично, как разность сигналов на пятом и седьмом резисторах, образован сигнал В (фиг. 3б), которому соответствует вектор

(фиг. 2), однако этот сигнал не изменяется от измеряемой величины. Сигнал В наблюдается между общей точкой пятого 2 и шестого 10 резисторов и общей точкой седьмого 5 и восьмого 13 резисторов.As a result of the current flowing through the first resistor 3, a signal A1 is formed on it (Fig. 3a), which corresponds to the vector

(Fig. 2), and as a result of the current flowing through the third resistor 4, a signal A3 is formed on it (Fig. 3a), which corresponds to the vector

(Fig. 2). The phases of the signals A1 and A3 do not coincide, but are shifted by an angle α (Fig. 2), the phase shift angle between the voltages of sources 7 and 8. The signal A1 changes in amplitude as a result of a change in the resistance of the first resistor 3 due to a change in the measured value. At the lower boundary of the measuring range, this signal corresponds to a vector

(Fig. 2). The signal B1 (Fig. 3A), which corresponds to the vector

(Fig. 2), equal to the difference of signals A1 and A3, is observed between the common point of the first 3 and second 11 resistors and the common point of the third 4 and fourth 12 resistors. Signal B1 changes in amplitude and phase due to a change in signal A1, i.e. as a result of a change in the measured quantity. This signal at the lower boundary of the measuring range corresponds to the vector BI _n (Fig. 2). Similarly, as the difference of the signals at the fifth and seventh resistors, signal B is formed (Fig. 3b), which corresponds to the vector

(Fig. 2), however, this signal does not change from the measured value. Signal B is observed between the common point of the fifth 2 and sixth 10 resistors and the common point of the seventh 5 and eighth 13 resistors.

(фиг. 2). Суммарный сигнал С изменяется по амплитуде и по фазе при изменении сигнала В1 из-за изменения измеряемой величины. На нижней границе диапазона измерений сигналу С соответствует вектор

(фиг. 2).Signal B1 is supplied to the first and second inputs of adder 17, and signal B is in antiphase to signal B. Using adder 17, signal B is subtracted (summed in antiphase) from signal B1, as a result of which signal C is generated at the output of adder 17 (Fig. 3b), which corresponds to the vector

(Fig. 2). The total signal C changes in amplitude and phase when the signal B1 changes due to a change in the measured value. At the lower boundary of the measuring range, signal C corresponds to a vector

(Fig. 2).

 Similarly to signal B, signal 0 is formed (Fig. 3b), which corresponds to the vector O (Fig. 2). The signal O is equal to the difference of the signals at the ninth 1 and eleventh 6 resistors and does not change when the measured value changes. This signal is observed between the common point of the ninth 1 and tenth resistors and the common point of the eleventh 6 and twelfth 14 resistors.

Information about the measured value is carried by the phase γ (Fig. 2) of the total signal C, counted from the phase of the signal O, taken as the reference point. At the lower boundary of the measurement range, this phase corresponds to a phase angle γ _n (Fig. 2).

Phase transformation γ, i.e. the conversion of the measured value into a signal at the output of the measuring transducer, convenient for observation, is carried out as follows. The signal O arrives at the first and second inputs of the first comparator 16, at the output of which pulses are generated (Fig. 3c) of duration T / 2 (T is the voltage period of sources 7 and 8), and the total signal C goes to the first and second inputs of the second comparator 20, at the output of which pulses are formed (Fig. 3d) of the same duration. At the outputs of block 15, pulses are generated (Fig. 3d, e, g) with a duration of several periods T (for example, 2T, as shown in Fig. 3), formed as a result of a change in the sign of the voltage of the first source 7 supplied to the first and second inputs of the block 15. In this case, such a pulse appears first at the first output of the control unit 15 (Fig. 3d), then at its second output (Fig. 3e), then at the third output (Fig. 3g). After that, the pulse appears again at the first output of block 15, then at the second output, etc. in a cycle that are repeated during the entire operating time of the transmitter. The pulse from the first output of block 15 is sent to zeroing the counter 21 pulses, from the second output to the fourth input of element And 19, from the third output to the second input of memory device 22. During the pulse at the second output of block 15 (Fig. 3e) in each operation cycle the measuring transducer element And 19 transmits pulses from the output of the pulse generator 18 to the counting input of the counter 21, (Fig. 3h), and for the first period T ₁ (Fig. 3e) the number of pulses n _{1 is} passed, and for the second period T ₂ (Fig. 3e) n ₂ pulses (Fig. 3h). Each of the numbers n ₁ and n _{2 is} proportional to the angles γ ₁ and γ ₂ (Fig. 3b). Observed respectively during periods T ₁ and T ₂ . These angles are the measured instantaneous values of the angle γ (Fig. 2), which is used to judge the measured value, and although the latter during the period T ₁ has the same value as during the period T ₂ (Fig. 3e) (measured value practically does not change during 2T), the angles γ ₁ and γ ₂ and the numbers n ₁ and n ₂ may not be equal to each other due to the presence of random small noise, which, for example, has the character of fluctuations. During the total time T ₁ and T ₂ in the counter 21 pulses accumulates the number N of pulses equal to the sum of the numbers n ₁ and n ₂ . The number N is proportional to the angle γ and more accurately reflects it in digital form than each of the numbers n ₁ or n ₂ , since it is less prone to distortion by fluctuation noise (due to the summation of the samples).

 The number N comes from the output of the counter 21 pulses to the first input of the storage device 22, which is an address input. The device 22 is a permanent storage device, in the cells of which with numbers (addresses) from the l-th to the m-th numbers are stored (written) equal to the discrete values of the measured quantity in the range from lower to upper values. With the arrival of a pulse (Fig. 3g) from the third output of block 15 to the second input of the storage device 22, the output of the last of its cells at number N receives a number equal to the current value of the measured value, which is displayed on block 23. When the measured value changes, the angle changes γ, and therefore, the number N, which determines the cell number of the device 22, changes, so that the number recorded in the N-th cell is always equal to the current value of the measured value.

 Thus, in each operating cycle of the measuring transducer, the pulse counter 21 is first reset to zero, then the number N is accumulated in it, and then a number equal to the current value of the measured value, which can be observed visually, is received from the cell N of the memory device 22 at the input of the block 23.

 The control unit 15 (Fig. 4) contains a third comparator 24, a frequency divider 25 and a decoder 26. The inputs of the comparator 24 (Fig. 4) are the inputs of the control unit 15 (Fig. 1). The output of the comparator 24 is connected to the input of the frequency divider 25, the output of which is connected to the input of the decoder 26. The three outputs of the decoder 26 are three outputs of the control unit 15.

 In the positive half-periods of voltage E1 (Fig. 5a) of the first voltage source 7, pulses (Fig. 5b) of duration T / 2 are generated at the output of comparator 24. Using a frequency divider 25, which can be used as a binary counter, these pulses are converted into pulses at its output (Fig. 5c) of duration T. The latter are transmitted to a decoder 26, at the three outputs of which pulses are sequentially generated in a cycle (Fig. 5g) , e, e).

Claims (1)

 MEASURING TRANSMITTER, comprising a series-connected first voltage source, first and second resistors, series-connected second voltage source, third and fourth resistors, the voltage sources being made as AC voltage sources, their first outputs and first outputs of the first and third resistors are connected to a common bus , the resistors are made so that the resistance of the first of them depends on the measured value, and the resistances of the others do not depend on it, element And, first, second the third inputs of which are connected respectively to the outputs of the first comparator, the second comparator and the pulse generator, the output is connected to the counting input of the pulse counter, the output of which is connected to the first input of the storage device, and the nulling input is connected to the first output of the control unit, the second output of which is connected to the fourth input element And, and the input is connected in parallel with the first voltage source, and an indication unit, characterized in that, in order to increase the accuracy of measurements, a fifth and a sixth resistor connected in series to the first voltage source, a seventh and eighth resistor connected in series to the second voltage source, a ninth and tenth resistor connected in series to the first voltage source, an eleventh and twelfth resistor connected in series to the second voltage source, further the introduced resistors are made so that their resistance is independent of the measured value, the first outputs of the fifth, seventh, ninth and eleventh resistors ditch connected to a common bus, an adder, the first and second inputs of which are connected respectively to a common point of the first and second resistors and a common point of the third and fourth resistors, the third and fourth inputs are connected respectively to a common point of the fifth and sixth resistors and a common point of the seventh and eighth resistors and the first and second outputs are connected respectively to the first and second inputs of the second comparator, and the first and second inputs of the first comparator are connected respectively to a common point of the ninth and tenth res Hur and the common point of the eleventh and the twelfth resistor, and a third control unit output is connected to the second input of the memory device, whose output is connected to the input of the indication unit.

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