Abstract:The bandwidth of the low pass filter in its signal conditioning circuits of the hard bearing dynamic balancing machine is less than that of the signal, so frequency characteristics of the circuits should be compensated. Generally, the compensated frequency characteristics are calculated with nominal values of the electronic components. To ensure the effect of compensation, dozens of filtering resistances and capacitors should be screened or matched strictly, which is of time consuming and cost ineffective. And the compensation effect will be degraded when temperature drift and time drift of element parameter occurs. This paper investigates an insitu and selfcontained frequency compensation method, to identify the frequency response characteristics of the third order lowpass filter circuit with the system’s original hardware and software resources. The selection of the exciting frequencies is investigated. The parameter estimation error caused by replacing the sine wave excitation with the square wave and triangular wave is analyzed. The frequency compensation experiments and performance verification of the hard bearing dynamic balancing machine are conducted. Experimental results prove the effectiveness of the proposed insitu frequency compensation method.