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美国的H-P公司生产的534A型计数器据称是一台达到直流至500兆赫直接计数能力的往复式计数器(reciprocal counter)。往复技术可允许1赫至500兆赫的一切输入频率的测量时间约为1秒钟,并保持稳定的九位数分辨率。一只500兆赫的时钟被用来使单次触发时间间隔分辨率达2毫微秒。在重复信号时,此分辨率还可改善到小于2微微秒。此外,该计数器还能自动地测量脉冲调制的射频载波。
The 534A counter from H-P in the United States is said to be a reciprocal counter capable of direct counting from DC to 500 MHz. Reciprocating techniques allow a measurement time of about 1 second for all input frequencies from 1 Hz to 500 MHz and maintain a stable nine-digit resolution. A 500 MHz clock was used to achieve a single trigger time interval resolution of 2 nanoseconds. This resolution can also be improved to less than 2 picoseconds when repeating a signal. In addition, the counter automatically measures the pulsed RF carrier.