Feige Mona, Schlamminger Stephan, Koffman Andrew D, Jarrett Dean G, Payagala Shamith, Panna Alireza, Waltrip Bryan C, Berilla Michael, Seifert Frank, Wang Yicheng
Quantum Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD 20899 USA.
IEEE Trans Instrum Meas. 2021;71. doi: 10.1109/tim.2021.3139709.
We tested a digital impedance bridge in a hybrid structure for comparison of a capacitor with a resistor where the impedance ratio was measured in two separate parts. The modulus of the impedance ratio was matched arbitrarily close to the input-to-output ratio, in magnitude, of a two-stage inductive voltage divider by adjusting the operating frequency of the bridge; the residual deviation between the two together with the phase factor of the impedance ratio was measured using a custom detection system based on a four-channel 24-bit digitizer. The ratio of the inductive voltage divider was calibrated, , using a conventional four-arm bridge with two known capacitors. Fluctuations of the source voltages were largely removed through postprocessing of the digitized data, and the measurement results were limited by the digitizer error. We have achieved an overall bridge resolution and stability of 0.02 μF/F in 2 h for measuring a 100-pF capacitor relative to a 12 906-Ω resistor at 1233 Hz. The relative combined standard uncertainty ( = 1) is 0.13 μF/F, dominated by the digitizer error.
我们在一种混合结构中测试了一个数字阻抗电桥，用于比较一个电容器和一个电阻器，其中阻抗比在两个独立部分进行测量。通过调节电桥的工作频率，使阻抗比的模在大小上任意接近一个两级电感分压器的输入与输出之比；使用基于四通道24位数字转换器的定制检测系统测量两者之间的残余偏差以及阻抗比的相位因子。电感分压器的比值使用带有两个已知电容器的传统四臂电桥进行校准。通过对数字化数据的后处理，很大程度上消除了源电压的波动，测量结果受数字转换器误差限制。在1233赫兹下，相对于一个12906Ω的电阻器测量一个100皮法的电容器时，我们在2小时内实现了电桥整体分辨率和稳定性达到0.02微法/法。相对合成标准不确定度（ = 1）为0.13微法/法，主要由数字转换器误差主导。
