电气专业英语课文翻译(6)

前面我们已经提到，人们在模拟转换器、信号调节器和A/D转换器等的使用上已经积累了大量的经验。因此，目前大部分的系统自然都采用这些技术。然而，还有很大一部分测量方法实质是数字的，在个别的测量仪中使用这些方法时，需要用到一些积分电路，如频率计数和计时电路等来提供指示输出。另外，如果把这种转换器和电脑相连的话，就可以省去一些器材；因为很多有积分电路执行的工作可以由计算机程序代为执行。

Collins classifies the signals handled in control and instrumentation systems as follows:

(1) Analog, in which the parameter of the system to be measured although initially derived in an analog form by a sensor is converted to an electrical analog, either by design or inherent in the methods adopted;

(2) Coded digital, in which a parallel digital signal is generated, each bit radix weighted according to some predetermined code. These are referred to in this book as direct digital transducers;

(3) Digital, in which a function, such as mean rate of a repetitive signal, is a measure of the parameter being measured. These are subsequently referred to as frequency domain transducers.

柯林斯把在控制和测量系统中处理的信号分为以下几类：

（1）模拟式。尽管系统的被测数最初通过传感器得到的是模拟信号，然后通过设计或采用原有的方法将模拟形式的信号转换成电模拟信号。

（2）数字码式。产生的信号是并行的数字信号，每一位的基数权重由预先编定的号码系统决定。在本书中这些仪器称作直接数字转换器。

（3）数字式。其中的函数是指测量参数时用到的量度标准，如对重复信号取平均值。这些仪器在后来称为频域转换器。

Some analog transducers are particularly suited to conversion to digital outputs using special techniques. The most popular of these are synchros, and similar devices, which produce a modulated output of a carrier frequency. For ordinary analog use, this output has to be demodulated to provide a signal whose magnitude and sign represent any conventional A/D technique to produce a digital output, there are techniques by which the synchro output can be converted directly to a digital output while providing a high accuracy and resolution, and at a faster rate than is possible in the A/D converter method.

特别地，一些模拟转换器适合用一些特别的技术来把模拟量转换成数字输出。其中最通用的方法是同步法和相似仪器的方法，即产生载波频率的调制输出的方法。在用作普通的模拟量输出仪器时，输出量必须经过解调。解调后输出的是直流信号，支流信号的大小和方向描述了转换器运动元件的偏移。虽然使用传统的

Direct digital transducers are, in fact, few and far between, since there do not seem to be any natural phenomena in which some detectable characteristic changes in discrete intervals as a result of a change of pressure, or change of temperature etc. There are many advantages in using direct digital transducers in ordinary instrumentation systems, even if computers are not used in the complete installation. These advantages are::

(1) The ease of generating, manipulating and storing digital signals, as punched tape, magnetic tape etc.;

(2) The need for high measurement accuracy and discrimination;

(3) The relative immunity of a high level digital signal to external disturbances(noise);

(4) Ergonomic advantages in simplified data presentation(e.g. digital readout avoids interpretation errors in reading scales or graphs).

直接数字转换器实际上用得很少，因为在自然现象中很少有那种由温度变化、压力变化等因素作用而产生的可测量的离散的变化量。在普通的仪器系统中使用直接数字转换器有如下优点（即使在完成安装时不使用计算机）：

（1）容易产生、处理和存储信号，如打控带、磁带等；

（2）高精度和高分辨率的需要；

（3）高介数字信号对外部噪声的抗干扰性；

（4）在简化数据描述时的人机工程学优势（例如：数字读出器能避免读刻度或图表时的判度错误）。 The most active development in direct digital transducer has been in shaft encoders, which are used extensively in machine tools and aircraft systems. High resolution and accuracies can be obtained, and these devices may be mechanically coupled to provide a direct digital output of any parameter which gives rise to a measurable physical displacement. The usual disadvantage of these systems is that the inertia of the instrument and encoder often limit the speed of response and therefore the operating frequencies.

在直接数字转换器中最能起作用的发展是轴编码器。轴编码器在机床和飞行系统中被广泛应用。利用这些设备能达到很高的精度和分辨率，而且这些设备能进行激动连接，给出任何可测量物理偏移的直接数字输出。这类系统通常的缺点是仪器的惯性及编码器限制了相应的速度，因而也限制了操作频率。

Frequency domain transducers have a special part to play in online systems with only few variables to be measured, since the computer can act as part of an A/D conversion system and use its own registers and clock for counting pulses or measuring pulse width. Access and process the transducer output. In designing such systems, consideration must be given to the computer time required to access and process the transducer output data.

频域转换器在线系统（测量量较少时）有着特殊的地位。因为计算机能担当A/D转换系统的部分工作，能用它自己的寄存器和时钟来计算脉冲和测量脉冲宽度。在这种系统的设计中必须考虑到计算机存取和处理转换器输出所需的时间。

Information systems combine several functions and devices. These systems provide an approach to the complex problem of measuring, using, and evaluating the mass of data and information produced by modern instrumentation, test, and control installations. Information and data handling systems are the next logical step from centralized control, graphic panels, and, multipoint recording systems. They present many data in logic form and balance the work performed by an operator and the automatic instrumentation system. They are widely used in industrial processes, test cells, and research and development laboratories to save time, increase accuracy of readings, reduce human error, and release skilled technicians for more important duties.

信息系统结合了许多功能和装置。这些系统提供了一个方法的复杂问题的测量 …… 此处隐藏：4770字，全部文档内容请下载后查看。喜欢就下载吧 ……