脉冲高电压测量不确定度评定

Evaluation of uncertainty in measurement of high voltage pulse

为开展脉冲高电压测量不确定度评定,分析了应用黑箱概念建立测量不确定度模型的方法,给出了脉冲分压器测量与标定的不确定度模型。依照不确定度传播率,对完善后的模型进行不确定度合成,并与通常采用的按照方差进行相对不确定分量合成的结果进行比较。计算结果表明:当不确定度模型中仅仅存在不同变量的乘除形式,或虽然存在加减项,但是其数学期望值为0,相对不确定度合成可以得到正确的结果。对通过测量2个电压间接计算电位差的方法以及用分贝表示衰减的不确定度合成开展分析,验证了相对不确定度合成的适用范围。在分压器标定实验中,为了减小信号源输出值的分散性对评定结果的影响,对电压比值开展A类不确定度评定,合成后得到分压比不确定度。

An uncertainty model has been proposed which is based on the black-box concept to evaluate the uncertainty of measurement and calibration in high voltage pulse divider. The initial model was proposed in principle, unnecessary variables in the formula could be omissible in the calibration experiment. For the model absent of uncertainty originating from calibration doc- ument, and resolving power of oscilloscope, the correction components which belong to the black-box model would be introduced to the formula to perfect the model. The uncertainties were combined after perfection of model according to the law of propagation of uncertainty. The results are compared with that combined from relative uncertainty. It is shown that the uncertainty combined from relative uncertainty will be correct if this model is only composed of multiplication and division of different variables, or addi- tion and subtraction of different variables are also permitted if the mathematical expectation values of these items equal to zero. This is proven by calculating the voltage potential between two different positions according to the measured voltage pulse at those positions and analyzing the attenuation represented by dB scales. In the calibration experiment of high voltage divider, the corn bined standard uncertainty of divider＇s scaling factor is obtained by evaluating Type A standard uncertainty of the ratio of output to input. The influence of dispersion from signal source output on evaluation of standard uncertainty can be weakened with this method.