Phase difference measuring apparatus and mass flowmeter thereof

Details Phase difference measuring apparatus and mass flowmeter thereof Phase difference measuring apparatus and mass flowmeter thereof

1995-09-12

1998-06-16

Brock, Michael

Electricity: measuring and testing

Measuring, testing, or sensing electricity, per se

Frequency of cyclic current or voltage

73861356, G01R 2500, G01F 184

Patent

active

057676658

ABSTRACT:
A phase difference measuring apparatus for accurately measuring the phase difference (fine time difference) of two signals with the same frequency with a reduced number of bits for A/D conversion is disclosed. In addition to output signals of an upstream side pickup and a downstream side pickup of a mass flowmeter, an output signal of the upstream side pickup or the downstream side pickup is supplied to a comparator, a PLL circuit, an antialiase filter, a sample and hold circuit, and an A/D converter. These circuits quantize these signals and send the quantized signals to a band pass filter. The band pass filter extracts a predetermined signal component and outputs it to a DFT. The DFT performs complex Fourier transformation on the input signal. Thus, the phase difference between two signals with the same frequency (such as an upstream side pickup signal and a downstream side pickup signal) can be accurately detected with a reduced number of bits for each of the A/D converters.

REFERENCES:
patent: 3513385 (1970-05-01), Pascoe
patent: 3895294 (1975-07-01), Vinding
patent: 4934196 (1990-06-01), Romano
patent: 5050439 (1991-09-01), Thompson
patent: 5052231 (1991-10-01), Christ et al.
patent: 5069074 (1991-12-01), Young et al.
patent: 5460033 (1995-10-01), Lew et al.
patent: 5469758 (1995-11-01), Kalotay

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