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在电学和声学测量中常需测量两个直流电压的相对幅度并用分贝表示,通常采用模拟集成运放组成的对数放大器来实现对数比测量。这样要用两个集成运放实现对数转换,而由第三个运放进行减法运算,在这种工作方式中,如果希望达到0.1db 的测量精度,要求对数放大器在整个动态范围内转换线性优于1%,因此需要对电路元件的温度变化进行细微的补偿调整。采用上无十四厂生产的7106/7107单片 CMOS31/2位 A/D 转换器可以实现双输入电压的对数比显示。由于7106/7107具有内部自动调零及优良的测量精度等优点,因此采用7106/7107单片 A/D 转换器组成的分贝计电路不但线路极为简单,易于调准,而且测量精度高和具有较好的稳定性,一次实现了数字显示。实验表明该电路显示精度优于0.1db。
In electrical and acoustic measurements often need to measure the relative magnitude of the two DC voltages and expressed in decibels, usually using a logarithmic amplifier composed of analog integrated op amp to achieve logarithmic ratio measurement. This use of two integrated op amp to achieve logarithm conversion, subtraction by the third op amp, in this mode of operation, if you want to achieve 0.1db measurement accuracy, logarithmic amplifier is required to convert the entire dynamic range The linearity is better than 1%, so fine adjustments to the temperature changes in the circuit components are required. The use of non-fourteen factory production 7106/7107 monolithic CMOS31 / 2-bit A / D converter can achieve dual input voltage log ratio display. As the 7106/7107 with internal auto-zero and excellent measurement accuracy, so the use of 7106/7107 monolithic A / D converter composed of decibel circuit is not only the line is extremely simple, easy to align, and the measurement accuracy and have more Good stability, once the digital display. Experiments show that the circuit shows better than 0.1 db.