Coordinated Ratiometric Compensation for High-Precision Load-Cells
First Claim
1. A method of performing ratiometric measurement, the method comprising:
- receiving a supply voltage signal;
supplying the received supply voltage signal directly to operate a transducer having a signal gain from an input to an output, the signal gain being substantially proportional to the supply voltage, and wherein the transducer is a load-cell;
supplying the received supply voltage directly to a compensation circuit;
generating from the compensation circuit an offset signal and a reference signal;
coupling an output of the transducer to an input of an amplifier;
coupling the output of the amplifier to an input of an analog-to-digital converter (ADC);
coupling the reference signal to the ADC, the reference signal making a dynamic range of the ADC substantially proportional to a dynamic range of the transducer; and
coupling the offset signal to the amplifier, the offset signal centering the dynamic range of the output of the amplifier within a dynamic range of the input of the ADC.
1 Assignment
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Accused Products
Abstract
Apparatus and associated methods relate to a load-cell measurement system having an output that is substantially independent of the system voltage source, by providing compensation for the source voltage variation using both a compensating offset voltage and a compensating reference voltage, these compensating voltages having a predetermined relationship with each other. In an illustrative example, the supply voltage may be directly connected to a load-cell, an instrumentation amplifier, and a compensation circuit. In some examples, the compensation circuit may include a chain of impedances which may generate two mutually related voltages both being scaled to the supply voltage. The first scaled voltage may, for example, substantially compensate offset of the load-cell measurement system. The second scaled voltage may, for example, substantially compensate for gain. In various examples, the compensating offset voltage and gain voltage may have a predetermined relationship so as to provide coordinated compensation of the system.
8 Citations
20 Claims
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1. A method of performing ratiometric measurement, the method comprising:
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receiving a supply voltage signal; supplying the received supply voltage signal directly to operate a transducer having a signal gain from an input to an output, the signal gain being substantially proportional to the supply voltage, and wherein the transducer is a load-cell; supplying the received supply voltage directly to a compensation circuit; generating from the compensation circuit an offset signal and a reference signal; coupling an output of the transducer to an input of an amplifier; coupling the output of the amplifier to an input of an analog-to-digital converter (ADC); coupling the reference signal to the ADC, the reference signal making a dynamic range of the ADC substantially proportional to a dynamic range of the transducer; and coupling the offset signal to the amplifier, the offset signal centering the dynamic range of the output of the amplifier within a dynamic range of the input of the ADC. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A measurement system comprising:
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a transducer that is biased with a supply voltage, the transducer having an output terminal, the output terminal having an offset and a gain, the offset and the gain being both proportional to the supply voltage; an amplifier having an input terminal, an output terminal, and an offset adjust terminal, the input terminal of the amplifier being connected to the output terminal of the transducer; an analog-to-digital converter (ADC) having an input terminal, an output terminal and a reference terminal, the input terminal being connected to the output terminal of the amplifier, and the input of the ADC having a dynamic range proportional to the reference; a first scaled measure of the supply voltage connected to the offset adjust terminal of the instrumentation amplifier; and a second scaled measure of the supply voltage having predetermined relationship to the first scaled measure, the second scaled measure being connected to the reference terminal of the ADC. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A measurement system comprising:
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a transducer that is biased with a supply voltage, the transducer having an output terminal, the output terminal having an offset and a gain, the offset and the gain being both proportional to the supply voltage; an amplifier having an input terminal, an output terminal, the input terminal of the amplifier being connected to the output terminal of the transducer; an analog-to-digital converter (ADC) having an input terminal, an output terminal, the input terminal being connected to the output terminal of the amplifier; means for compensating the gain variation caused by the variable supply voltage using a first scaled measure of the supply voltage; and means for compensating the offset variation caused by the variable supply voltage using a second scaled measure of the supply voltage having a predetermined relationship to the first scaled measure. - View Dependent Claims (18, 19, 20)
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Specification