Accurate and responsive weighing apparatus with drift compensation
First Claim
1. A weighing apparatus for weighing a load and for providing a digital weight signal used to display the weight of the load comprising:
- at least one weighing means, said weighing means further comprising;
a weight detector for detecting the weight of the load and outputting an analog weight signal;
an amplifier for amplifying the analog weight signal; and
an analog filter with a first cut off frequency for reducing a high frequency component of the amplified analog weight signal which is higher than said first cut-off frequency; and
at least one delta-sigma analog-to-digital converter, said converter further comprising;
a modulator for modulating the amplified analog weight signal output from the analog filter into a digital signal, anda digital filter with a second cut-off frequency for reducing a high frequency component of the digital signal which is higher than said second cut-off frequency, wherein the second cut-off frequency is higher than the first cut-off frequency, thereby to provide the digital weight signal.
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Abstract
In order to increase both the weighing accuracy and the weighing speed of a weighing apparatus, a delta·sigma analog-to-digital converter (4) having a cut-off frequency higher than that of an analog filter (3) is connected with the output of the analog filter (3). Also, in order to perform a quick drift correction of an amplifier (2), the analog filter (3) is selectively switchable so as to perform a filtering function during a weighing mode and to perform a buffering function during a correction mode correcting means (52) is provided for storing the digital signal from the delta·sigma analog-to-digital converter (4) as a drift signal (df) during the correction mode and for providing a corrected digital weight signal (d2) by subtracting the drift signal (dr) from the digital weight signal (d1) obtained from the delta·sigma-type analog-to-digital converter (4) during the weighing mode.
11 Citations
16 Claims
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1. A weighing apparatus for weighing a load and for providing a digital weight signal used to display the weight of the load comprising:
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at least one weighing means, said weighing means further comprising; a weight detector for detecting the weight of the load and outputting an analog weight signal; an amplifier for amplifying the analog weight signal; and an analog filter with a first cut off frequency for reducing a high frequency component of the amplified analog weight signal which is higher than said first cut-off frequency; and at least one delta-sigma analog-to-digital converter, said converter further comprising; a modulator for modulating the amplified analog weight signal output from the analog filter into a digital signal, and a digital filter with a second cut-off frequency for reducing a high frequency component of the digital signal which is higher than said second cut-off frequency, wherein the second cut-off frequency is higher than the first cut-off frequency, thereby to provide the digital weight signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A weighing apparatus for weighing a load and for providing a digital weight signal used to display the weight of the load comprising:
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at least one weighing means, said weighing means further comprising; a weight detector for detecting the weight of the load and outputting an analog weight signal; an amplifier for amplifying the analog weight signal; and an analog filter with a first cut off frequency for reducing a high frequency component of the amplified analog weight signal which is higher than said first cut-off frequency, wherein the first cut off frequency is of a value corresponding to a mechanical vibration of the weight detector; and at least one delta-sigma analog-to-digital converter said converter further comprising; a modulator for modulating the amplified analog weight signal output from the analog filter into a digital signal, and a digital filter with a second cut off frequency for reducing a high frequency component of the digital signal which is higher than said second cut-off frequency, wherein the second cut-off frequency is higher than the first cut-off frequency, thereby to provide the digital weight signal. - View Dependent Claims (13, 14, 15, 16)
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Specification