Galvanic isolation of analog signals with improved metrological characteristics

The disadvantages of galvanically isolated converters that transmit information through an insulating barrier in digital or analog form are considered, such as the high cost of components or a conversion error of more than 1 %. Such galvanically isolated converters are necessary for the safe operation of equipment operating at voltages above 50 V. A galvanic analog signal separator has been developed that transmits information in analog form through an insulating barrier without transferring it (converting it) to digital form and has a conversion error of 0.22 % at rated voltage. This galvanic separator can be used as part of measuring devices such as converters, sensors, and analog signal transceivers without transferring information to digital form. A method of transmitting an analog information signal in the absence of an electrical connection is investigated, which makes it possible to reduce the error and increase the noise immunity of the converter.The circuit of the proposed galvanic analog signal separator is based on negative feedback, the circuit of which passes through a modulator, transformer and demodulator on the primary side. The signal from the output of the demodulator is sent to one of the two inputs of the error amplifier. The error amplifier adjusts the voltages at both inputs in strict accordance with each other, due to which the voltage at the output of the demodulator is exactly equal to the input voltage supplied to the other input of the error amplifier. The second demodulator, identical to the first one, is installed on the secondary side. The use of two demodulators made it possible to achieve accurate transmission of the analog signal from the primary side to the secondary side. A laboratory sample of a galvanic analog signal separator has been manufactured and tested. According to the test results, the expediency of using negative feedback has been confirmed: the relative conversion error has been reduced by three times compared to devices without feedback. The relative error of the conversion of the proposed device over the entire input voltage range was no more than 0.7 % and 0.22 % at the nominal input value. The device can be used as part of measuring equipment operating at high (more than 10 kV) voltages.

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