SU1170368A1 - Voltage root-mean-square value-to-constant voltage measuring converter - Google Patents

Abstract

MEASURING CONVERTER OF MEDIUM SQUARE VALUES FOR DC CONSTANT VOLTAGE, containing a triangular voltage generator, the output of which is connected to the first inputs of two voltage limiters, a low-frequency filtering device, the output of which is connected to an output bus bar and a second piece of a beater, a beater, a beater, a beater, a low-speed beater, a low-frequency filtering device whose output is connected to an output bus bar and a second beater, and a beater is attached to a single-piece belay tool, a low-speed beater, a low-frequency filtering device, whose output is connected to an output bus and a second beater, and a second piece of a beater is attached. connected to the input bus, characterized in that, in order to increase accuracy and increase the dynamic range, it additionally introduces an amplitude rectifier whose input is connected to the input bus and an output to the input of a triangular voltage generator, made in the form of a single generator (L polar voltage and subtractive. unit, connected between the outputs of voltage regulators and the input of a low-frequency filtering device .

Description

I The invention relates to electrical measuring equipment and can be used in voltmeters of the rms voltage. A linear converter of the rms voltage to a constant voltage, the contents of a rectifier, an amplitude converter, a generator of a different polarity triangular voltage, two comparison devices, the AND circuit, the key, and the 1D integrator are known. In the known converter, a wide input voltage range is provided, however, the sensitivity of its quad is approximately two times lower than that of quadrants with a single-pole triangular voltage. In addition, the converter is characterized by an error caused by a voltage ripple at the output of the amplitude rectifier. The ripple level of this voltage depends on the constant discharge of the amplitude capacitor in the system. An increase in the constant discharge leads to an increase in the transient process with a decrease in the amplitude of the input voltage and, consequently, to a decrease in the speed of the converter. Consider the effect of the amplitude rectifier output voltage ripple on the conversion error, considering the input voltage to be sinusoidal (and sincot), then for the output voltage of the amplitude rectifier you can get the following approximate expression that is sinusoidal for a half period. signal (from one maximum to another maximum of the rectified sine wave)). The average value of this voltage, which is taken as the amplitude of the triangular voltage, is IT 2V, 2CUn-r. -T / 2t-) f J idv) J 1 o s is the time constant of the amplitude rectifier; T is the period of sinusoidal voltage. The variable component of the output voltage of the amplitude rectifier is in) i, i) -idv, p. This component is added to the input voltage input voltage (in this case, sinusoidal), 8 is squared and gives a non-zero constant displacement, which determines the conversion error. We define it, m, 2. Jc (H4 nnWco5 (oi-2: JUftn (ilco6 (oiJi- °. T / 4. |. |,.). And „.- No. and„ with „al-jfe (, - /“), U .. o "ajt .. SchJb and I-... The sign of approximate equality is explained by the fact that the exponential function decomposes into a power series. The relative error of the transformation is determined by the formula with c" - 2Us, 2TU2 0 | - where - squared rms "value of sinusoidal voltage. Thus, the ripple error from the output voltage of the amplitude rectifier is large, especially when the converter is operated at low frequencies, for example 50 Hz. When the error is 1% o should be on the order of 1.3 s, which is unacceptable for industrial converters, since their establishment time should not exceed 0.3-0.5 s. The closest to the technical essence of the invention is a measuring converter of rms value a constant voltage, containing a generator of a triangular polarized voltage, connected to the first inputs of the two limiters. The second input of the first delimiter is the input of the converter. The outputs of the limiters are connected to the inputs of a low-frequency sum-filtering device, the output of which through the polarity limiter and the modulator is connected to the second input of the second limiter AND However, this converter has inherent disadvantages: low sensitivity, which decreases in proportion to the square of the root-mean-square value of the input voltage and, in therefore, narrow dynamic range and large errors when working with low voltages. Indeed, the output average value of the voltage (U. „) At the output of the limiter is (1) where Ux is the RMS of the voltage to be converted; triangular amplitude. From the expression (1) it is seen that And decreases, with decreasing Ux according to a quadratic law. For example, with decreasing and y by 10 times and decreasing by 100 times. This leads to the fact that dramatically increases the error of the instability of the zero summing filtering device. It can be obtained from - & P - ™ Ap where fp is the error due to drift zero. If we consider the zero drift of the operational amplifier to be 10 V / C, the conversion limit is 1 V, the amplitude coefficient of the input voltages is 2, while A 2B, From expression (2), the relative error of 10 ° C at U) (0.1 V; drd, 8%, which corresponds to a reduced error of 0.8%) can be calculated. Such an error is not permissible in modern rms voltage converters The purpose of the invention is to improve the accuracy of conversion and expansion of dynamic Converted voltage range. The goal is achieved by the fact that, in the measuring transducer,: rms voltage to constant voltage, containing a triangular voltage generator - the output of which is connected to the first inputs of two voltage limiters, the filtering device is low the frequency, the output of which is connected to the output bus and to the second input of the first voltage limiter, the second input of the second voltage limiter is connected to the input bus, additionally contains amplitude output DC converter having an input connected to the input hydrochloric bus, and an output - to the input of the generator of a triangular voltage generator vsholnennogo a uni-p- Nogo voltage and the subtracting unit. connected between the outputs of the voltage limiters and the input of the low-frequency filtering device. In FIG. 1 shows a flowchart of a converter; in fig. 2 voltage diagrams at characteristic points of the converter. ./ The rms voltage to DC voltage measuring converter contains a triangular voltage generator 1, the output of which is connected to the first inputs of two voltage limiters 2 and 3, a low-pass filtering device of frequency 4 whose output is connected to the output bus and with the second input of the first voltage limiter 2, the second input of the second voltage limiter 3 is connected to the input bus. An amplitude rectifier 5 is added to the converter, the input of which is connected to the input bus and the output to the input of the triangular voltage generator 1. The triangular voltage generator 1 is made in the form of a unipolar voltage generator. A subtraction unit (not shown) is connected between the outputs of voltage suppressors 2 and 3 and the Low-frequency Filtering device 4. - The RMS voltage-to-voltage measuring transducer operates as follows. After supplying the transformable voltage I (t) to the input of the transformer, voltage taps 2 and 3 are formed at the outputs of voltage limiters 2 and 3, respectively, Uv (t) 7r-. U4. (T) ff-; (3) 2А 2А l Hell is the root-mean-square value of the input voltage; - output constant voltage; - the amplitude of the triangular voltage. The voltage at the output of the low-frequency filtering device 4, which is the output DC voltage of the converter, is (t) -U3 (t) Ujy, (4) de KU is the gain of the filtering device 4. Substitute in the output (4 a) relation (3) we obtain UjtlL Uia-ЦЖ «2А„ 2А „, From here .1Т бых. u, K .. The equal sign is satisfied with the error HocTi io less than 0.01% already at Cc 300: Thus, the output constant voltage is directly proportional to the rms value of the input voltage. Let us estimate the relative error caused by the drift zero of the filtering device 4,,. then p .5A.i. 5 - - - - AGi KA ".Ug ,, ft where and., .. ,,„., The maximum value oh max. - coefficient of input voltage amplitude; K - proportionality factor converted the amplitude of the input voltage to the amplitude of the triangular voltage. We estimate the error value in the proposed transformation under the same conditions as in the prototype, Ki 1.1 (corresponds to the ripple level of 10%), in that case 0.8% 1.1 0.9%. This corresponds to a given error of 0.1%. There is no error in the measuring transducer caused by the ripple of the output voltage of the amplitude rectifier. This can be seen from the plots of voltages at the output of the individual converter blocks shown in FIG. 2. Since in the converter the triangular voltage is unipolar U (i (t), the zero level of the triangular voltage is not subjected to amplitude modulation by the output voltage of the amplitude rectifier. At the output of the limiters and U). (T) J is the difference difference voltage between) and (t); Ua (t) and Up; ((t). As can be seen from the voltage plots) and U (t) J f, it does not depend on the ripple of the output voltage of the amplitude rectifier, i.e. conversion accuracy does not depend on voltage ripple). Due to the fact that the amplitude of the triangular voltage A varies in proportion to the input voltage level 3d (t) between the changes in the input voltage level Ug (t) and its square, as follows from relations (3), the relationship is proportional to. For this reason, the measuring transducer has an extended dynamic range and a significantly reduced conversion error, especially at low input voltage levels. Thus, the use of the proposed triangular voltage generator with the possibility of generating a unipolar voltage with an amplitude proportional to the amplitude of the input voltage through an amplitude rectifier, as well as the filtering of its device, allows one to expand the dynamic range converter and improve conversion accuracy. In order to ensure the conversion of the bipolar voltage, it can be fed to the input of the converter through any of the known full-wave measuring rectifiers.

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Claims (1)

RMS VOLTAGE VOLTAGE CONVERTER TO DC VOLTAGE, containing a triangular voltage generator, the output of which is connected to the first inputs of two voltage limiters, a low-frequency filter device, the output of which is connected to the output bus and the second input of the first voltage limiter, the second input of the second input of the second voltage limiter with an input bus, characterized in that, in order to increase the accuracy and expand the dynamic range, an amplitude is additionally introduced into it tudny rectifier input of which is connected to an input bus and an output - to an input of a triangular voltage generator, made in the form of a single voltage generator and the subtracting unit, connected between the output voltage limiters and the input low frequency filtering device. I 1170368