Frequency measurement signal processing circuit

Abstract

The invention provides a frequency measurement signal processing circuit. The frequency measurement signal processing circuit comprises a high pass filtering circuit for carrying out high pass filtering of input signals to filter DC input signals of the input signals, a signal superposition circuit used for superposing an AC input signal outputted by the high pass filtering circuit with a compensation signal, a low pass filtering circuit carrying out low pass filtering of AD / DC superposition signals of the signal superposition circuit, outputting a to-be-detected AC / DC signal which is taken as an output signal of a frequency measurement signal processing circuit, and a signal compensation circuit, wherein a compensation signal is generated by the signal compensation circuit according to a preset level and the to-be-detected AC / DC signal, the compensation signal is used for compensating an error between a common mode level and a preset level in the AD / DC superposition signals, and the compensation signal is outputted by the signal compensation circuit to the signal superposition circuit to make the common mode level be constantly equal to the preset level. According to the frequency measurement signal processing circuit, a common level of the input signals can be raised to a fixed value same as a certain fixed level value, only common elements are used, the structure is simple, and low cost, high precision and small errors are realized.

Description

technical field [0001] The invention relates to the field of circuits, in particular to a low-cost, high-precision frequency measurement signal processing circuit used in precision instruments and meters. Background technique [0002] In the previous single-supply power supply system, the frequency measurement circuit needs to raise the common-mode level of the input signal to a fixed value that is the same as a certain fixed level value, and then the comparator compares the fixed level with the input signal. If there is an error between the common mode level and the fixed level of the input signal, it will affect the frequency measurement of the AC small signal in the input signal. Regardless of raising the common-mode level of the input signal or dividing the voltage to obtain a fixed level, external resistors are required. To make the common-mode level and the fixed level as equal as possible, high-precision resistors must be used. If the instrument needs To ensure accur...

AI Technical Summary

Problems solved by technology

If there is an error between the common mode level and the fixed level of the input signal, it will affect the frequency measurement of the AC small signal in the input signal

Regardless of raising the common-mode level of the input signal or dividing the voltage to obtain a fixed level, external resistors are required. To make the common-mode level and the fixed level as equal as possible, high-precision resistors must be used. If the instrument needs To ensure accuracy in a wide temperature range, the selected resistor must also be a low-temperature drift resistor, and high-precision low-temperature drift resistors are not commonly used, and the price is also expensive, which will greatly increase the cost of the frequency measurement circuit

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