Voltage-step transient experiments are used to calibrate electrodiffusion (ED) friction probes. The approach is demonstrated on the probes in high-speed rotating impellers. This calibration has shown that shear rates as high as 10(6) s(-1) can be measured reliably using 0.5 mm Pt working electrodes in ferro/ferricyanide aqueous solutions. The complete transient calibration experiment provides sufficient information about the dynamics of ED friction probes.