Through analyzing, this paper points out four main methods which is used today to measure electrical power. By comparison, all of those methods can’t be employed to measure audio-frequency power efficiently. However, considering the basic principle that electrical power is the product of voltage and electrical current, this thesis designed a digital audio measuring circuit which is composed of sampling circuit, product operation circuit, level switching circuit, A/D circuit and LED displaying part to measure both direct current electric power and low-frequency alternating current electric power, in other words, it can work under a wide working range from direct current to audio frequency. To sine-wave single-frequency signals, complex waveform signals and speech signals, the circuit can directly carries out the active power, really consumed by the load, of which the measuring error is not more or less than 3%. This circuit, which is considered to be simple, reliable and low-cost, measures the active power in an effective way within a wild working range. This design overcomes former deficiencies such as the testing complexity, low precision and high-cost equipment. And the power is displayed in digital number which is convenient for reading. In addition, it can not only be single used, but also inner installed in the related equipments, thus it can realize the digital measurement of direct current and low-frequency power. However, one of the shortcomings of this design is that the longer it works, the larger measuring error is.
Key words:
audio-frequency electrical power; analog multiplier; digital power meter; design.
