SU480025A1 - Converter of the ratio of two voltages to the time interval - Google Patents

Description

one .

The invention relates to a measurement technique and can be used in digital measuring instruments and converters of analog values into a digital code for converting the ratio of two voltages into a time interval, one of which voltages can be a reference.

A known converter is a ratio of two applications in a time interval, consisting of analog switches, an integrator, an inverting amplifier, a comparator, and a digital control circuit (device 3450A manufactured by Hewlett-Packard, USA), operating on the principle of double integration.

The disadvantage of this circuit is the necessary presence of an inverter, the higher conversion error and the complexity of the instrument circuit.

The purpose of the invention is to improve the accuracy of conversion and modification of the circuit.

This is achieved by the fact that the integrator and comparator are made on differential amplifiers, one inputs of which are connected together and connected via analog switches to the common point of the circuit, the first and second inputs of the converter, and the second input of the integrator is also connected via analog switches to the second input of the converter General point of the scheme.

The drawing is a diagram of the proposed Converter.

The converter contains analog switches 1-5, an integrator consisting of a differential amplifier 6, a capacitor 7 and a resistor 8, a comparator on a differential amplifier 9, and a digital control unit 10.

The converter has a first input terminal 11 and a second input terminal 12, a common wire terminal 13 and a converter output terminal 14.

The Converter operates as follows.

The switching sequence is determined by the control unit 10. The measured signals are supplied to the first input 11 and the second input 12. In the initial position, the keys 4 and 5 are conductive, and the keys 1, 2 and 3 are in a non-conductive state. At the output of the comparator 9, the voltage is zero.

In the first position, the keys 3 and 4 are in the conducting state, and the keys 1, 2, and 5 are in the non-conducting state. The comparator 9 is constrained, and there is a voltage at its output. The capacitor 7 is charged. The duration of this position is determined by the high precision of the control unit.

In the second position, two cases are possible. If the polarities of the voltage across the inputs 11 and 12 are the same, then the keys 1 and 5 are conductive, and the keys 2, 3 and 4 are in a non-conductive state. If the polarities of the input voltages are different, the keys 2 and 4 are conductive, and the keys I, 3 and 5 are in a non-conductive state. In both cases, the process lasts until the point in time when the capacitor 7 is discharged and the voltage at the output of the comparator 9 is equal to zero.

The time interval between the beginning of the second position of the keys and the onset of zero voltage at the output of the comparator is proportional to the ratio of the voltages applied to inputs 11 and 12.

P r d -M et inventions

A converter of the ratio of two voltages to a time interval containing analog switches, a digital control circuit, an integrator and a comparator, characterized in that, in order to improve accuracy and simplify the circuit. together and via analog switches are connected respectively to a common point of the circuit, the first and second inputs of the converter, and the second input of the integrator is also connected via analog switches

with the second transducer and a common point of the circuit.

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