Digital frequency selection measuring system capable of resisting one hundred thousand times of interference

Abstract

A digital frequency selection measuring system capable of resisting one hundred thousand times of interference relates to the technical field of measurement. A voltage measurement function front-end circuit of the digital frequency selection measuring system comprises a voltage measuring terminal, an automatic range switching unit, a filter circuit unit and an isolation and amplification unit, a CPU (central processing unit) transmits a signal to control the automatic range switching unit to automatically switch ranges, the automatic range switching unit is connected to the filter circuit unit, the filter circuit unit is connected to the isolation and amplification unit, and output of the isolation and amplification unit is connected to the CPU. A current signal of a current measuring terminal is inputted to an automatic range switching unit, the CPU transmits a signal to control the automatic range switching unit to automatically switch ranges, the automatic range switching unit is connected to a filter unit, the filter unit is connected to an operational amplification unit, the operational amplification unit is connected to the CPU, and the CPU carries out analytic processing. The digital frequency selection measuring system can realize frequency selection measurement with resistance to one hundred thousand times of interference on the basis of + / -1Hz, and has important application in the field of electric measurement, particularly in the field of test of electric systems under the background with high interference.

Description

Technical field [0001] The invention relates to the field of measurement technology. Background technique [0002] Most electrical equipment runs under 50Hz power frequency AC voltage. In many cases, it is necessary to measure the state parameters at power frequency 50Hz, most of which are directly measuring voltage and current signals, or converting various physical quantities into voltage and current signals through sensors and then measuring . Due to the strong 50Hz interference in the power grid, it is difficult to measure some weak test signals in the field due to strong interference with 50Hz, which often brings great errors or even cannot be measured. Therefore, in many electrical parameter test items, the different frequency method can be used to measure, that is, add a sine wave signal source different from the power frequency such as 55Hz to the equipment, and then use frequency selective filtering technology to suppress 50Hz interference, and only measure the 55Hz sig...

AI Technical Summary

Problems solved by technology

However, the analog filter circuit has the following disadvantages: 1. It can only suppress and attenuate interference, but cannot completely filter out interference

2. The analog filter circuit is suitable for the situation where the difference between the test signal and the interference frequency is large (such as 120Hz and 50Hz), and it is difficult to achieve the ideal effect for two very close frequencies (such as 51Hz and 50Hz); 3. It is affected by the characteristics of the hardware circuit itself Its anti-interference ability can only reach one tenth; 4. Because the hardware circuit has inconsistent response characteristics to different frequencies and amplitudes, it is difficult to ensure accurate measurement at each frequency and range; 5. Analog circuits are not conducive to intelligence. automation, integration

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