SU924590A1 - Voltage rms value converter - Google Patents

Description

one

The invention relates to electrical measuring equipment and is intended for use in the creation of ammeters and voltmeters of the mean square value.

The known converter of the mean square value of voltage contains an electrothermal comparator, one of the inputs of which is connected to the output of the amplifier with an adjustable transmission coefficient, and the other input to the output of the source of the reference voltage, an amplifier of noncompensation, the input of which is connected to the output of the electrothermal comparator, and the output through control unit - to the control input of the amplifier with adjustable transmission coefficient I.

The drawback of the device is that the frequency band of the voltage being converted is narrow.

The closest technical re-. The proposed offer is

mean square stress generator containing

VI electrothermal comparator, the first of the inputs of which is connected to the output source of the reference voltage, the second input to the output of the amplifier with an adjustable transmission coefficient and to the first input of the discrete scale converter unit, which includes a generator

to the pulses, and the output through the non-compensating amplifier to the first input of the switch, the second input of which is connected to the common input of the device, and the First output to one of the inputs

ts amplifier with adjustable transmission ratio, memory unit whose input is connected to the second output of the switch, and output to another input of the amplifier with adjustable transmission coefficient, comparison unit, the first input of which is connected to the output of the discrete scaling unit (Converter, and the second input - with

one of the outputs of the auxiliary voltage source, the other output of which is connected to the third input of the switch, the control unit, the first output of which is connected to the second input of the discrete scale conversion unit, the second output to the fourth input of the switch, the third output to the indicator input, and - with the output of the comparison block 2.

The drawback of the device is associated with a small frequency band with a large adjustable feedback depth of the amplifier due to the difficulty of ensuring stable operation of the amplifier throughout the entire control range.

The purpose of the invention is to expand the frequency range of the voltage to be converted.

The goal is achieved by the fact that in the converter of the mean square voltage, containing an electrothermal comparator, the first of the inputs of which is connected to the output of the Source of the exemplary voltage, and the output to the input of the non-compensation amplifier, the switch, one of the signal inputs of which is connected to the common input of the device, the other the signal input is with the output of the non-homogenous amplifier, and the control input with the first output of the control unit, a pulse generator, a comparison unit, two pulse counters, a trigger are entered , pulse-width modulator, two keys and a coincidence unit, the counting input of the first pulse counter is connected to the output of the pulse generator directly, and the counting input of the second pulse counter — through the first of keys whose control input is connected to the output of the match block, Both of the pulse counters are connected to the inputs of the comparison unit, the output of which is connected to one of the trigger inputs, the other trigger input is connected to the high-level output of the first counter% 1 pulses, and the output to the control input The second switch is installed between the switch output and the second input of the electrothermal comparator, the reset input of the second pulse counter is connected to the second output of the control unit, the signal input of the pulse-width modulator is connected to the output of the uncompensation amplifier, the clock input is to the third output of the control unit, and the output to one of the inputs of the coincidence unit, the other input of which is connected to the fourth output of the control unit.

The drawing shows the functional diagram of the rms voltage converter .i

The device contains a switch 1, a switch 2, an electrothermal comparator 3, a source C of the reference voltage, a non-compensation amplifier 5, a pulse-width modulator 6, a coincidence unit 7 (AND gate), a switch 8, a pulse generator 9, a pulse counter 10 pulses, a block 11 comparisons, a pulse counter 12, a trigger 13 and a control unit T.

The device works as follows.

The operation takes place in two cycles. In the first cycle, the switch 1 closes to the position in which the electrothermal comparator 3 is connected via the key 2 and the switch 1 to the input of the device. The measured voltage is supplied to the input of the thermal heating comparator 3 during the time intervals determined by the pulse duration T from the output of the trigger 13 and formed with a constant period T specified by the AND control unit. The trigger 13 is set to one at the time of the overflow of the pulse counter 12 and to the zero state when the codes in the counters 10 and 12 pulses are equal. The installation in the zero state of the counter 10 is made by the control unit k at the end of each period T.

The rms value of a sequence of pulses proportional to the compensation voltage of the comparator 3 corresponds to

-u.vf.

(one)

and

OS,

Formed a closed-loop static system of the first order tends to become equal

(2)

and

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wasps

where is the constant voltage from the output of the source and the exemplary voltage. Taking into account (1), we have

(3)

Claims (2)

Uo Ux After the end of all transients, the control unit l inhibits the passage of pulses from the output of the pulse-width modulator 6 through the block 7 to the control input of the switch 8. At the same time, in the pulse counter 1 there remains a code proportional to the voltage UQC moment of establishing equality Uoe, Ue,. In the second cycle, the control unit k switches the switch 1 to a position in which a pulse sequence with an amplitude equal to the output voltage amplitude with the same constant period T specified by the control unit 1 and the pulse duration T fixed to the electrothermal comparator 3 is supplied The counter has 10 pulses at the end of the first clock cycle. The resulting closed static system tends to an equilibrium state in which the root-mean-square value of the pulse sequence becomes equivalent to the constant voltage of the source of the reference voltage source k / L -. Since in the second cycle T, T, Uo remained the same (and as at the end of the first cycle, it follows from (3) and C) that they are UO, (5) from where From expression (6) it is clear that the converter has There is a linear conversion of the rms value of the input signal into a constant voltage. The converter operates at one point of the characteristics of an electrothermal comparator. 3- Converting the uncompensation voltage to a time interval, memorizing that time interval and replacing an amplifier with an adjustable gain to a key that can be opened for a fixed time interval, allows the frequency range of the converter to be significantly extended. Claims of the RMS voltage converter containing an electrothermal comparator, the first of which inputs are connected to the output of an exemplary voltage source, and the output to the uncompensation amplifier input, a switch, one of the signal inputs of which is connected to the common input of the device, another signal input - with the output of the non-compensating amplifier, and the controlling input - with the first output of the control unit, the pulse generator, a comparison unit, characterized in that, in order to extend the frequency range is converted voltage, a further two pulse counter introduced, a trigger pulse-pulse. modulator, two keys and a coincidence unit, the counting input of the first pulse counter is connected to the output of the pulse generator directly, and the counting input of the second pulse counter through the first of keys, the control input of which is connected to the output of the coincidence unit, the bit outputs of both counters the pulses are connected to the inputs of the comparison unit, the output of which is connected to one of the trigger inputs, the other trigger input is connected to the high-voltage output of the first pulse counter, and the output to the controlled input of the second key set between the output of the switch and the second input of the electrothermal comparator, the reset input of the second pulse counter is connected to the second output of the control unit, the signal input of the pulse-width modulator is connected to the output of the uncompensation amplifier, the clock input to the third output of the control unit, and the output to one From the inputs of the coincidence unit, another input of which is connected to the fourth output of the control unit. Sources of information taken into account in the examination 1. P. Ornatsky Automatic measurements and instruments. K., School, 1971, p. 509-510. 2. USSR author's certificate number 221163, cl. G 01 R 19/26,1966.