dbu,dbm,dbv
电压电平（voltage level）的定义是：某一电压V与一基准电压Vr相比求常用对数乘以20以dB表示的值为电压V的电压电平。即由于Vr取值的不同，常用的电压电平单位有下列三种：
A、dBm 由于1mW电功率在600Ω阻抗上的电压可算得为0.775V，所以Vr=0.775V所求得的电压电平，单位也可写为dBm。 由于当设RΩ阻抗上的电功率为P，并设Rr=600Ω时，
如R=Rr=600Ω，则
所以这时以dBm表示的电压电平与相应的电功率电压数值相等。如R≠Rr=600Ω，则
即以dBm表示的电压电平应为以Vr=0.775V求得的电压电平加上修正项10lgR r/R才与相应的电功率电平dBm值相等。B、dBu 如果只考虑电压电平本身，不考虑是否与相应的电功率电平之间的关系，那么求电压电平时，就可以不管阻抗是否为600Ω，即不管上述的修正项。这样，当以Vr=0.775V为基准电压时所求得的电压电平单位为dBu。C、dBv 以Vr=1V为基准电压时所求得的电压电平值，单位为dBv。目前 dBu 通用于广播方面，如调 音台的调音设备及电气测试设备及仪表等。 dBv比较通用于声学及其它测试仪器。600Ω用dB换算表（以1mW为0dB）0dBm以下电 平（dBm）0dBm以上电压（V）电流（mA）电功率（mW）电压（V）电流（mA）电功率（mW）0.77461.2911.000-0+0.77461.2911.0000.6951.1510.794310.86911.4481.2590.61531.0260.631020.97521.6251.5850.54840.91400.501231.0941.8231.9950.48870.81450.39814102282.0472.5120.43560.72600.316251.3772.2953.1620.38820.64700.251261.5462.5773.9810.34600.57670.199571.7342.8905.0120.30840.51400.158581.9463.2436.3100.27480.45800.135992.1833.6387.9430.24490.40820.100102.4494.08210.0000.21830.36380.07943112.7484.58012.590.19460.32430.06310123.0845.14015.850.17340.28900.05012133.4605.76719.950.15460.25770.03981143.8826.47025.120.13770.22950.03162154.3567.26031.620.12280.20470.02512164.8878.14539.810.14940.18230.01995175.4849.14050.120.097520.16260.01585186.15310.2663.100.086910.14480.01259196.90511.5179.430.077460.12910.01000-20+7.74612.91100.000.043560.072600.003162513.7722.95316.20.024490.040820.001003024.4940.821.000W0.013770.022950.0003163543.5672.603.162W0.0077460.012910.0001004077.46129.0010.000W0.0043560.007260 0.000031645137.7229.531.62W0.0024490.0040820.0000150244.9408.2100W0.0013770.0022950.0000031655435.6726.0316.2W0.00077460.0012910.00000160774.61.291A1000W0.00043560.00072600.0000003166513772.295A3162W0.00024490.00040820.00000017024494.082A10000W0.00013770.00022950.00000003167543567.260A31620W0.000077460.00012910.0000000180774612.910A100000W 看了,把它粘了下来,放进文件夹里.
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