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本文以31/2位A/D转换器5G14433为例,利用其欠量程、过量程信号并使用微机控制,以特有的显示方式——增加小信号数字直读位数,提高测量精度。 A/D转换器是数字仪表的心脏部分,但因数字电路的固有特性所决定。如5G14433的转换精度为0.05％,±1个字,由它所组成的数字电压表,在测量低电压时,测量精度实际上是较差的。以1.999V为满表度值的表头,当被测值在0～9 mV内,因只有个位数显示,A/D转换精度有±1个字的误差。因此,相对误差为:100％～10％,被测值在10～99mV内,此时显示二位数,相对误差10％～1％。由此知道,测量精度与被测的值有关,呈现的相对误差是不同的。因此,为提高测量精度,必须用较高级的仪表。而这在一般的实验室内是不容易满足的,或者作为某一装置的终端测量指示,设计位数较多的仪表,在技术上和经济上都是必须慎重考虑的。
In this paper, 31/2 A / D converter 5G14433, for example, the use of its under-range, over-range signal and the use of computer control, with a unique display - increase the small signal digital direct reading digits to improve measurement accuracy. A / D converter is the heart of digital instrumentation, but due to the inherent characteristics of digital circuits. Such as 5G14433 conversion accuracy of 0.05%, ± 1 word, composed of digital voltmeter which, in the measurement of low voltage, the measurement accuracy is actually poor. When the measured value is within 0 ~ 9 mV, the accuracy of A / D conversion is ± 1 word due to the single-digit display. Therefore, the relative error is: 100% ~ 10%, the measured value is within 10 ~ 99mV, at this time shows two digits, the relative error of 10% to 1%. This shows that the measurement accuracy is related to the measured value, showing the relative error is different. Therefore, in order to improve the measurement accuracy, it is necessary to use more advanced instruments. However, this is not easily satisfied in general laboratories, or as a terminal measurement instructions for a device, the design of a larger number of bits of the instrument, both technically and economically must be carefully considered.