SU949527A1 - Ac voltage rms value to dc voltage converter - Google Patents

Description

the first thermistor converter and a modulator and a resistor with a heater of the second thermistor converter 2. A disadvantage of the known converter is the low sensitivity and low conversion accuracy in the presence of noise of the thermistor converters, the drift and the zero offset of the used amplifiers. The aim of the invention is to increase the sensitivity and accuracy of the conversion in a wide frequency range to transform voltages. The goal is achieved by the fact that in the converter of the rms value of alternating voltage to constant, containing the first and second thermistor converters, the first outputs of the heater of which are connected to the common bus, the second output of the heater of the first ones of the marine transducer is connected to the combined first outputs of the first and second limiting resistors , the second output is the first of which is connected to the input bus the second output of the heater of the second thermistor converter is connected to p The first output of the third limiting resistor, and the first output of the thermistor of this converter is connected to the common bus, the source of the reference voltage, the first output of which is connected to the common bus, and the second through the voltage divider to the first input of the first operational amplifier, the second input of which is connected the second output of the thermistor of the first thermoresistor converter, and the second operational amplifier, the output of which is connected to the output bus, are additionally introduced the second voltage divider, the third operational voltage A second amplifier, a voltage adder, a controlled voltage divider and an amplifier-limiter, the second output of the thermistor of the first thermistor converter connected to the output of the first operational accelerator and the first input of the second operational amplifier, the second input of which is connected to the second output of the voltage source and the first input of the third operational amplifier, the second input of which is connected to the output bus through the second voltage divider, and the output to the second output of the second limiting cut the source and the first input of the voltage adder, the output of which is connected to the second output of the third limiting resistor and the second input to the output of the controllable voltage divider, the control input of which is connected to the output bus, the input to the output of the amplifier of the limiter, the input connected to the input bus, and the second view of the thermistor of the second thermistor converter is connected to the second input of the first operational amplifier. The drawing shows a block diagram of a constant-voltage converter. The rms-to-rms rms converter contains input bus 1, thermistor converters 2 and 3 (TRP), operational amplifiers (OA) 4-6, reference voltage source 7 (ION), voltage dividers 8 and 9 (DN) , voltage adder 10, output bus 11, controllable voltage divider 12, amplifier limiting 13, limiting resistors 14-16. Thermistor converter 2 contains heater 17 and thermistor 18, and thermistor converter 3 contains heater 19 and thermistor 20. Input bus 1 is connected to the first output 1 of resistor 14 and the input of the limiting amplifier 13, the second output of resistor 14 is connected to the first output of resistor 15 and the first output of the heater 17, the second output of which is connected to the common bus, the second output of the resistor 15 is connected to the first input of the adder 10 and the output of the operational amplifier 5, the first outputs of the heater 19 and the thermistor 20 are connected a common bus, the second output of the heater 19 is connected via a resistor 16 to the outputs of the adder 10, the second input of which through a controlled divider 12 is connected to the output of the amplifier-limiter 13, the control input of the controlled divider -12 is connected to the output bus 11, to the output of the operating amplifier 4 and through the divider 9 with the first input of the operational amplifier 5 / whose second input is connected to the output of the source 7 of the reference voltage, to the first EFF input of the operational amplifier 4 and through the divider 8 - with the first input of the operational amplifier 6, the output is oh connected to the second input of the operational amplifier 4 and the first output of the thermistor 18, the second output of which is connected to the second input of the operational amplifier 6 and the second output of the thermistor 20. The converter operates as follows. In the initial state, in the absence of the measured voltage U; j (t) on the bus 1 of the converter, the voltage from the output of ION 7 through the first 8 DN, whose transmission coefficient is 1/2, goes to the non-inverting input of the operational amplifier 6,

the output of which appears a voltage equal to

 EEL + Eg. Rje

and,

one)

theirs (

-2

2.0

where Ej, is the output voltage of the ION;

1 R, p - resistances of thermistor resistors TRP 2 and 3.

If the resistances and RjO are equal at both inputs of the operational amplifier 4, the voltage and voltage are equal in magnitude and sign, so that at its output at the inverting input of the amplifier 5 and on. bus 11 of the converter, the constant voltage t, is equal to zero (i.e., O- Voltage Eg from the output of the ION enters the non-inverting input of amplifier 5, the output voltage of which through the limiting resistor 15 goes to heater 17 of TRP 2, and through the adder 10 and limiting resistor 16 to heater 19 of TRP 3 and used to output operating points of TRP to the linear portion of their conversion characteristics. When applying the measured voltage Ux (t) to bus 1 of the converter in heater 17 of TRP 2, additional heat is released Joel ,by The effect of which decreases the resistance value of thermistor 18 and the output voltage of the amplifier b in accordance with fault (1). The difference between the output voltages of the amplifier b and ION 7 is amplified by an op-amp 4 whose output voltage U is applied to the control input of the controlled divider 12. At the same time, the input voltage DX (t) is fed to the input of the amplifier-limiter 13, which forms two-pole rectangular pulses with coherent levels, the frequency and phase of which coincides with the frequency phase y (t), and the level / pulses dependent on the level Ux (t). The rectangular pulses from the output of the amplifier-limiter 13 through the controlled divider 12, the adder voltage 10 and the limiting resistor 16 are fed to the heater 19 TRP G As a result, the thermistor 20 is changed to establish a balance at which the output voltage of the amplifier 6 will be close to output voltage of ION 7. In a steady state constant eg. hard u | bix. The output of amplifier 4 (on converter bus 11, the polarity of which corresponds to the polarity of the output voltage of the ion source) will be proportional to the actual value of the alternating voltage Ux (t) at the input of the converter. Part of the voltage output of the amplifier 4 through the DN 9 enters the inverting

the input of the amplifier 5, the output voltage of which decreases, keeping almost unchanged (with the error of the OS statism) the initially set temperature mode of operation of both TRP.

The sensitivity of the conversion of the proposed converter is increased by eliminating the constant resistors connected in series with the thermistors of the TRD, which reduce the value of the relative change in the resistance of the thermistors.

The accuracy of the converter is enhanced in a wide frequency range due to the fact that both heaters 17 and 19 of the PLC operate in almost the same frequency mode, which significantly reduces the effect of their residual reactivity on the conversion error.

Thus, the use of the proposed converter in the measuring equipment of alternating current allows to increase their metrological and operational characteristics (sensitivity, accuracy in a wide range, frequency and speed).

Claims (2)

Invention Formula The rms voltage to rms converter contains the first and second thermistor converters, the first terminals of the heaters of which are connected to a common bus, the second output of the heater of the first te1 of the Resistor converter is connected to the combined first terminals of the first and second limiting resistors, the second output of the first of which is connected with the input bus, the second output of the heater of the second thermistor converter is connected to the first output of the third limit the first resistor of the converter is connected to the common bus, the source of the reference voltage, the first terminal of which is connected to the common bus, and the second through the voltage divider - to the first input of the first operational amplifier, the second input of which is connected to the first output of the thermistor the first thermistor transducer, and the second operational amplifier, the output of which is connected to the output bus, characterized in that, in order to increase the sensitivity and accuracy of the conversion, We have a second voltage divider, a third operational amplifier, a voltage adder, a controlled voltage divider and an amplifier-limiter, the second output of the thermistor of the first thermistor converter is connected to the output of the first operational amplifier and the first input of the second operational amplifier, the second input of which is connected to the second the output of the reference voltage source and the first input of the third operational amplifier, the second input of which is connected through the second divider; with the output bus, and the output with the second output of the second limiting resistor and the first input of the voltage adder, the output of which is connected to the second output of the third limiting resistor, and the second input with the output of the controlled voltage divider, the control input of which is connected to the output bus input - with the output of the amplifier-limiter, the input of which is connected to the input bus, and the second output of the thermistor of the second thermistor converter is connected to the second input of the first operational amplifier, Sources of information taken into account in the examination 1 Volgin L.I. Measuring converters of alternating voltage in constant. M., Soviet Radio, 1977, p. 146, fig. 146. 2. Patent of Great Britain 1138932, cl. GOl R 19/00, 11.04.69 / taeototype).