Description:
<jats:p>We tested a simple digital impedance bridge using two nominally equal resistors to
form a 1:1 ratio. We focused on resolution and stability of the detectors. Fluctuations
of the source voltages were largely removed through postprocessing of the digitized
data, and the measurement results were limited by the detector noise. This
detector-limited operating condition was first demonstrated using three modified
Keysight 3458A multimeters for measurements of the voltage ratios, achieving 0.01 μV/V
type A uncertainty in less than 15 min at 1 kHz. In an effort to extend the applicable
frequency range and develop a system with off-the-shelf components, we tested a system
using three lock-in detectors for measuring small deviations from the perfect AC ratio
of unity magnitude, achieving stabilities and resolutions of 0.1 μV/V in a few hours for
each point from 1 kHz to 5 kHz.</jats:p>