Dual frequency excitation is an innovative method that superimposes high frequencies on low frequencies, and utilizes the advantages while eliminating the disadvantages of the high and low frequency excitation methods. Namely, the flow noise immunity and fast response of the high frequency excitation method, and the high zero stability of the low frequency excitation method are realized simultaneously.

Consistency in noise immunity and zero stability

Noise in slurry or low conductivity fluid measurement is a function of 1/f, so the lower the frequency, the greater the noise. However, the conventional high frequency excitation method suffers from poor zero stability. The dual frequency excitation method ensures noise immunity with high frequency sampling, and also achieves high zero stability with a large time constant in low frequency sampling. As a result, the synthesized signals are almost noise-free and have exceptional zero stability.

Fast response of 0.1 sec

With the conventional pulsed DC frequency excitation method, the time constant must be large to minimize the effects of noise, but this also damps the flow signals and slows the signal response. In contrast, the dual excitation method captures changes in flow with high frequency sampling, allowing a fast response of 0.1 sec.