Isolated low-noise micro-current amplifier

Abstract

The invention discloses an isolated low-noise micro-current amplifier which is an amplifier circuit for amplifying micro-current of a reference measurement signal in a micro-coulometry analyzer. The isolated low-noise micro-current amplifier comprises an indicating electrode pair consisting of a reference electrode (12) and a measuring electrode (13) which are inserted into electrolyte, and an electronic switch A, and the isolated low-noise micro-current amplifier is characterized in that an energy amplifier (16) is arranged among the reference electrode (12), the measuring electrode (13) and the electronic switch A, and is used for amplifying a voltage signal for reflecting the concentration change of the electrolyte; the energy amplifier (16) mainly comprises a group of symmetrical positive and negative power supplies (22, 23) and a high input impedance operational amplifier (24); the output end of the electronic switch A outputs the voltage signal amplified by the energy amplifier (16). Therefore, the analysis precision of the micro-coulometry analyzer can be greatly improved, the 0.1ppm sample content can be detected under general analyzing and operating conditions, and the sample content greatly exceeds the detection lower limit of 0.2ppm specified in the industrial standard.

Description

technical field [0001] The invention relates to a microcoulomb analyzer used in the field of electrochemical analysis and an amplifier circuit capable of amplifying weak current of a reference measurement signal. Background technique [0002] The microcoulomb analyzer is used for the analysis of the total sulfur, chlorine and nitrogen elements in chemical products and the analysis of the content of inorganic salts. At present, the micro-coulomb analyzer produced by domestic manufacturers and foreign American Dorman Company is a closed-loop negative feedback system composed of a coulometric amplifier designed in a zero-balance working mode, a titration cell and a suitable electrolyte by applying the principle of micro-coulomb titration. . The titration cell is inserted with a reference electrode and a measuring electrode (indicating electrode pair) for measuring the concentration change of the sample, and an anode and a cathode (electrolytic electrode pair) for electrolyzing...

AI Technical Summary

Problems solved by technology

Since the electrochemical signal generated by the ions in the electrolyte on the measuring electrode and the reference electrode is very weak and can only be a potential, it is almost impossible to output current, and the signal obtained after the transition of the electronic switch is unstable.

After the signal is amplified by the amplifier, the noise is very large. If a certain circuit is used to reduce the noise in the amplifying circuit, the sensitivity of the instrument will also be reduced at the same time, and it is impossible to detect and analyze samples of ≤0.2ppm.

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