Sine wave generating circuit and method for measuring resistance and battery tester

Abstract

The invention provides a sine wave generating circuit for measuring resistance. The circuit comprises a CPU, a gate shaping circuit and a shaping and amplifying unit. The CPU generates two paths of square wave signals with a fixed duty cycle and transmits the signals to the gate shaping circuit. The gate shaping circuit converts the square wave signals into stepped waveform signals with alternating peaks and troughs. The shaping and amplifying unit converts the stepped waveform signals into sine wave signals. The sine wave generating circuit and the method for measuring resistance provided by the invention have the advantages of stable effect, low power consumption, high precision and are especially suitable for an occasion with large environment change and limited power supply such as wild, and the invention also provides a batter tester.

Description

technical field [0001] The invention relates to a sine wave generating circuit and method, in particular to a sine wave generating circuit and method for measuring resistance, and a storage battery tester. Background technique [0002] The battery tester, also known as the battery measuring instrument, is an analysis and testing equipment mainly used to measure the battery, which includes measuring the voltage, current, resistance, temperature, etc. of the battery, and then judging the working ability and health status of the battery. In the process of measuring resistance, the battery tester needs to use the sine wave as the reference signal for feedback and comparison. The advantage is that the sine wave is an alternating signal, which can avoid the DC interference of the battery and improve the detection accuracy. [0003] In the prior art, there are several methods for generating sine waves for measuring the resistance of the storage battery as follows: [0004] One is ...

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Problems solved by technology

The disadvantage of this circuit is: the amount of positive feedback is difficult to control. If the amount of feedback is less than 1 times, the circuit cannot overcome the internal loss and thus cannot generate self-excited oscillation. If the amount of feedback is too large, the circuit will output a square wave instead of a sine wave In addition, it is necessary to add a frequency selection network to achieve a single frequency output, otherwise the circuit will oscillate in a wide frequency range and generate many harmonics; at the same time, even if it can output a single frequency sine wave, the circuit itself is easily affected by the outside world. Environmental influences, such as temperature, humidity and other factors, cause frequency deviation and decrease in accuracy

The advantage of this method is strong anti-interference ability, adjustable, accurate and controllable frequency, but the disadvantage is that the CPU generates pulses with different duty ratios, which requires CPU resources and consumes a lot of power. When the battery tester is used for When in the field, its battery runs out quickly and the usage time is greatly reduced

The disadvantages are: due to the use of capacitor charging and discharging to generate a square wave, the stability of the square wave is easily affected by the capacitor itself, and it is prone to distortion during low-pass filtering, and the generated sine wave is unstable. In addition, it requires a large number of chips. high power consumption

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