英语翻译The value shown at +dV/dt indicates as a percentage of 500V,the size of voltage variations within 300m/sec.permitted before +dV/dt is only active as long as it is exceeded.

英语翻译The value shown at +dV/dt indicates as a percentage of 500V,the size of voltage variations within 300m/sec.permitted before +dV/dt is only active as long as it is exceeded.
英语翻译
The value shown at +dV/dt indicates as a percentage of 500V,the size of voltage variations within 300m/sec.permitted before +dV/dt is only active as long as it is exceeded.

英语翻译The value shown at +dV/dt indicates as a percentage of 500V,the size of voltage variations within 300m/sec.permitted before +dV/dt is only active as long as it is exceeded.
上述原文有语病：
The value shown at +dV/dt indicates as a percentage of 500V, the size of voltage variations within 300m/sec permitted before +dV/dt is only active as long as it is exceeded.
怎么能够有indicates和第一个is共同存在在一个句子里,究竟哪一个是主词,是The value shown at +dV/dt,还是the size of voltage variations within 300m/sec permitted before +dV/dt?
如果把句子断开,可有两种可能.
1. The value shown at +dV/dt indicates as a percentage of 500V, the size of voltage variations within 300m/sec. The value permitted before +dV/dt is only active as long as it is exceeded.
在+dV/dt所显示的值就等同与500伏的一个百分比,此百分比是发生在时速每秒300米每秒以内的电压变化幅度.只要该值超出额定范围（即+dV/dt ）的时候,该值就起作用（归纳为活性值）.
2.
The value shown at +dV/dt indicated as a percentage of 500V, being the size of voltage variations within 300m/sec permitted before +dV/dt, is only active as long as it is exceeded.
显示为500伏的一个百分比的+dV/dt值,即在+dV/dt所允许情况下的时速每秒300米内,若超出额定范围（即+dV/dt ）便会起作用（或归纳为活性值）.
The value shown at +dV/dt indicates as a percentage of 500V,the size of voltage variations within 300m/sec.permitted before +dV/dt is only active as long as it is exceeded.

仪表显示在+dV/dt 值就等同与500伏的一个百分率，电压变化大小在300米每秒以内。一旦超出额定范围（即+dV/dt ）的时候，仪器就不再运作了！
PS：由于不是电学专业的，所以难免可能会有偏差，望理解（但应该不会偏离很大）

价值被显示在+dV/dt 表明作为500V 的百分比, 电压变异的大小在300m/sec.permitted 之内在+dV/dt 是只活跃的之前只要它被超出。
大概``是这吧~