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DC voltage measurements
直流电压测量
作者:佚名
译者:佚名
Solid-state devices are always powered by direct currents and voltages . Vacuum tubes require DC voltage sources as well. Thus many measuremtents are made in the DC mode. Many systems today have built-in diagnostic meters so that power supply parmeters can be monitored and logged.

Accuracies of a typical DC bench-type digital multimeter can be as good as 0.002 percent (1 count of reading for a 6 1/2 digit instrument). This accuracy is often available on the lower voltage ranges usually below 300 V;for higher voltages accuracies may be slightly worse.

The point here is to read the instrument’s specifications carefully, and if things are not clearly spelled out, contact the instrument manufacturers’ application. engineering department.

High-voltage DC measurements usually involve a high-resistance voltage divider, which usually forms a high resistance to the circuit being measured and thus draws infinitesimal current. One common need for measuring DC voltages in the range of 2 to 30 kilovolts(kV)is in measuring cathode-ray tube(CRT) final anode voltages. Many CRTs used in colour television sets and computer monitors have voltages in the range of 15 to 30 kV. The accuracy of such measurements usually is not critical and should be in the range of 3 to 5 percent of the reading. A highly insulated hand-held probe containing the voltage divider is often used and comes as an accessory from some manufacturers.
固体状态设备总是以直流和电压为动力。真空电子管也要求以直流电压为电源。这样许多测量是采用直流模式的。许多系统现在都内装诊断仪以便电能供应参数能被监测和记录。

一台典型的直流台式数字万用表的精度可以达到0.002%(一种6 1/2 数字仪器的一个读数)。这种精度经常用于低电压范围(一般在300 V以下);对于更高的电压精确性可能稍微差点。

此处的要点是仔细地阅读仪器说明书,如果说明书上没有详细的说明,可与仪器制造商技术支持部门联系。

高压直流测量通常需要一个高阻抗的分压器,它对被测量的电路通常形成一个高电阻以便只有极小的电流被分流。对于测量2到30kV的直流电压,最普通的需要是测量阴极射线管(CRT)的决定电极。许多阴极射线管所包括的彩色显示器和智能探测器有15到30kV的电压。但是用阴极射线管所作测量的精度并不令人有所挑剔,它的精度在读数的3%到5%之间。一种高度绝缘的包括分压器的手持式探头经常被使用而且作为某些设备的附件来配备。
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