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由于本仪器是数字显示的,因此,仪器的关键问题是实现模数转换。本仪器的A/D转换器是双斜积分模数转换器。常规的双斜转换器一个测量周期有两个不同的阶段:1.输入信号积分;2.基准电压积分(反向积分)。输入信号被定时积分,其测量时间由时钟脉冲计数。然后,对一个极性相反的恒定的基准电压积分,直到积分器输出电压返回到零。基准积分时间恰恰与输入信号成正比。在这个时间内,计数器所计脉冲数即表示输入信号的平均值。图1是基本双斜转换器的方框图。图2是积分器输出波形图。
Since this instrument is digitally displayed, the key issue with the instrument is to achieve A / D conversion. The instrument’s A / D converter is a dual-skew integrated analog-to-digital converter. Conventional double-diagonal converters have two different phases for a measurement cycle: 1. Input signal integration; 2. Reference voltage integration (reverse integration). The input signal is timed and its measurement time is counted by the clock pulse. Then, a constant reference voltage of the opposite polarity is integrated until the integrator output voltage returns to zero. The reference integration time is exactly proportional to the input signal. During this time, the number of pulses counted by the counter means the average value of the input signal. Figure 1 is a block diagram of a basic double-diagonal converter. Figure 2 is the integrator output waveform.