System for digital weighing with zeroizing for thermal effects

Claim 1

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; means to turn on and turn off said switch; an analog-to-digital converter; means operative, with said switch on, for a weigh cycle of operation of the system to couple said converter to the output of the load cells for at least part of an operation of said converter so as to generate a digital output from an analog voltage output of the load cells due at least in part to the weight affecting the cells; means operative, only with said switch off, for a separate thermal zero cycle of operation of the system to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells; means to utilize said stored signal in said converter during a part only of the operation of said converter for the weigh cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said thermal voltage of the load cells; and control logic means to inhibit the operation of said means operative for said thermal zero cycle oF operation during the operation of said means operative for said weigh cycle of operation and to inhibit the operation of said means operative for said weigh cycle of operation during the operation of said means operative for said thermal zero cycle of operation.

Claim 2

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; means to turn on and turn off said switch; an analog-to-digital converter; means operative, with said switch on, for a weigh cycle of operation of the system to couple said converter to the output of the load cells for at least part of an operation of said converter so as to generate a digital output from an analog voltage output of the load cells due at least in part to the weight affecting the cells; means operative, only with said switch off, for a separate thermal zero cycle of operation of the system to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells; means to utilize said stored signal in said converter during a part only of the operation of said converter for the weigh cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said thermal voltage of the load cells; and control logic means to inhibit the operation of said means operative for said thermal zero cycle oF operation during the operation of said means operative for said weigh cycle of operation and to inhibit the operation of said means operative for said weigh cycle of operation during the operation of said means operative for said thermal zero cycle of operation.

Claim 3

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a first switch to couple the load cells to a power supply; means to turn on and turn off said switch; an analog-to-digital converter that includes: a preamplifier having an input to be coupled to the voltage output of the load cells; a second switch; means coupling the output of said preamplifier to said second switch; means to turn on and turn off said second switch; an integrator coupled to said second switch; a comparator coupled to the output of said integrator; a third switch; means coupling said third switch to said integrator to apply through said switch, when it is on and coupled to a reference voltage of opposite sign to the output voltage of said preamplifier, a voltage to said integrator; means to turn on and turn off said third switch; means to generate pulses at a predetermined frequency; timing means operatively coupled to said means to turn on and turn off said second switch and operatively coupled to said means to turn on and turn off said third switch whereby said timing means, when initiated, turns on said second switch for a predetermined period of time, and the turns off said second switch and turns on said third switch; signal-generating means responsive to the output of said comparator when it crosses zero volts while said third switch is on, to generate a signal; and counter means operatively connected to count pulses from said pulse-generating means when initiated by said timing means until signaled by said signal-generating means to stop counting; means operative when said first switch is off and when coupled to the output of the load cells in a thermal zero cycle of operation of the system to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells, said signal ang generating means including: a fourth switch coupled to the output of said preamplifier; means to turn on said fourth switch while said first switch is off; a second integrator coupled to said fourth switch; and an inverter coupled to the output of said second integrator and to another input of said preamplifier; meas to operatively couple said converter to the output of the load cells for at least part of an operation of said converter in a weigh cycle of operation of the system when said first switch is on to generate an analog voltage output by the load cells due to the weight affecting the cells; and means to utilize said stored signal in said converter during a part only of the operation of said converter for the weigh cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said thermal voltage of the load cells, said means to utilize stored signal includes: means to turn off said fourth switch when said first switch is turned on, whereby in said system said signal-generating and signal-storing means provides a signal corresponding to the thermal voltage as an input to said preamplifier and the output voltage of said preamplifier due to offset voltage and current of said preamplifier, and whereby said signal-utilizing means maintains the stored signal as an output by said inverter to be used for an input to said preamplifier to compensate for those effects during the time that the output of said preamplifier is integrated by said first integrator for the predetermined period of time.

Claim 4

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a first switch to couple the load cells to a power supply; means to turn on and turn off said switch; an analog-to-digital converter that includes: a preamplifier having an input to be coupled to the voltage output of the load cells; a second switch; means coupling the output of said preamplifier to said second switch; means to turn on and turn off said second switch; an integrator coupled to said second switch; a comparator coupled to the output of said integrator; a third switch; means coupling said third switch to said integrator to apply through said switch, when it is on and coupled to a reference voltage of opposite sign to the output voltage of said preamplifier, a voltage to said integrator; means to turn on and turn off said third switch; means to generate pulses at a predetermined frequency; timing means operatively coupled to said means to turn on and turn off said second switch and operatively coupled to said means to turn on and turn off said third switch whereby said timing means, when initiated, turns on said second switch for a predetermined period of time, and the turns off said second switch and turns on said third switch; signal-generating means responsive to the output of said comparator when it crosses zero volts while said third switch is on, to generate a signal; and counter means operatively connected to count pulses from said pulse-generating means when initiated by said timing means until signaled by said signal-generating means to stop counting; means operative when said first switch is off and when coupled to the output of the load cells in a thermal zero cycle of operation of the system to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells, said signal ang generating means including: a fourth switch coupled to the output of said preamplifier; means to turn on said fourth switch while said first switch is off; a second integrator coupled to said fourth switch; and an inverter coupled to the output of said second integrator and to another input of said preamplifier; meas to operatively couple said converter to the output of the load cells for at least part of an operation of said converter in a weigh cycle of operation of the system when said first switch is on to generate an analog voltage output by the load cells due to the weight affecting the cells; and means to utilize said stored signal in said converter during a part only of the operation of said converter for the weigh cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said thermal voltage of the load cells, said means to utilize stored signal includes: means to turn off said fourth switch when said first switch is turned on, whereby in said system said signal-generating and signal-storing means provides a signal corresponding to the thermal voltage as an input to said preamplifier and the output voltage of said preamplifier due to offset voltage and current of said preamplifier, and whereby said signal-utilizing means maintains the stored signal as an output by said inverter to be used for an input to said preamplifier to compensate for those effects during the time that the output of said preamplifier is integrated by said first integrator for the predetermined period of time.

Claim 10

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; means to turn on and turn off said switch; an analog-to-digital converter that includes: a voltage controlled oscillator having an input to be coupled to the output of the load cells to obtain at the output of said oscillator pulses with a frequency proportional to the voltage at its input; an up-down counter coupled, when enabled, to the output of said oscillator to count said pulses; and a clock to provide a first signal to enable said counter and later a second signal to gate close said counter, whereby said counter counts pulses from said oscillator for a predetermined period of time, said clock being coupled to said counter; means operative when said switch is off and when coupled to the output of the load cells to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells, said signal and generating means including: means to operatively couple said oscillator to said counter for an up count mode only during said predetermined time interval as a thermal zero cycle of operation of said converter while said switch is off; and first latch means coupled to said counter when signaled to enter in said first latch means the final output of said counter obtained by the thermal zero cycle of operation of said converter; means to operatively couple said converter to the output of the load cells, while said switch is on for at least part of an operation of said converter to generate an analog voltage output by the load cells due to the weight affecting the cells, that constitutes: means, while said switch is on, to operatively couple the output of said oscillator to said counter during said predetermined time interval as a weigh cycle of operation of said converter; and means to utilize said stored signal in said converter during a part only of the operation of said converter for a weigh cycle of operation of the system in a manner to provide a final digital output of said converter essen-tially devoid of any digital value representative of said thermal voltage of the load cells, said means to utilize said stored signal in said converter during a part only of the operation of said converter for the weigh cycle, which part is while said switch is on, comprising: means operative to reset said counter and at the start of said time interval to set said counter to the digital value of said first latch means, containing the stored value from a previous thermal zero cycle of operation of the system; means to change said counter to the down count mode at the start of said time interval; and means to change said counter to the up count mode when signaled by said counter that its count has decreased to zero during that time interval, said system further including: second latch means coupled to said counter when signaled to enter in said second latch means the final output of said counter obtained by the weigh cycle of operation of said converter; means responsive to a signal for a thermal zero cycle of operation to operate said switch-turning means to turn off said switch, to provide said coupling between said clock and said counter through said means operatively coupling said oscillator to said counter for counting during said time interval, and to provide at the end of said time interval a signal to said first latch means; and means responsive to a signal for a weigh cycle of operation to signal said switch-turning means to turn on said switch if off, to provide said coupling between said clock and said counter through said means operatively coupling said oscillator to said counter for counting during said time interval, and to provide at the end of said time interval a signal to said second latch means.

Claim 11

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; means to turn on and turn off said switch; an analog-to-digital converter that includes: a voltage controlled oscillator having an input to be coupled to the output of the load cells to obtain at the output of said oscillator pulses with a frequency proportional to the voltage at its input; an up-down counter coupled, when enabled, to the output of said oscillator to count said pulses; and a clock to provide a first signal to enable said counter and later a second signal to gate close said counter, whereby said counter counts pulses from said oscillator for a predetermined period of time, said clock being coupled to said counter; means operative when said switch is off and when coupled to the output of the load cells to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells, said signal and generating means including: means to operatively couple said oscillator to said counter for an up count mode only during said predetermined time interval as a thermal zero cycle of operation of said converter while said switch is off; and first latch means coupled to said counter when signaled to enter in said first latch means the final output of said counter obtained by the thermal zero cycle of operation of said converter; means to operatively couple said converter to the output of the load cells, while said switch is on for at least part of an operation of said converter to generate an analog voltage output by the load cells due to the weight affecting the cells, that constitutes: means, while said switch is on, to operatively couple the output of said oscillator to said counter during said predetermined time interval as a weigh cycle of operation of said converter; and means to utilize said stored signal in said converter during a part only of the operation of said converter for a weigh cycle of operation of the system in a manner to provide a final digital output of said converter essen-tially devoid of any digital value representative of said thermal voltage of the load cells, said means to utilize said stored signal in said converter during a part only of the operation of said converter for the weigh cycle, which part is while said switch is on, comprising: means operative to reset said counter and at the start of said time interval to set said counter to the digital value of said first latch means, containing the stored value from a previous thermal zero cycle of operation of the system; means to change said counter to the down count mode at the start of said time interval; and means to change said counter to the up count mode when signaled by said counter that its count has decreased to zero during that time interval, said system further including: second latch means coupled to said counter when signaled to enter in said second latch means the final output of said counter obtained by the weigh cycle of operation of said converter; means responsive to a signal for a thermal zero cycle of operation to operate said switch-turning means to turn off said switch, to provide said coupling between said clock and said counter through said means operatively coupling said oscillator to said counter for counting during said time interval, and to provide at the end of said time interval a signal to said first latch means; and means responsive to a signal for a weigh cycle of operation to signal said switch-turning means to turn on said switch if off, to provide said coupling between said clock and said counter through said means operatively coupling said oscillator to said counter for counting during said time interval, and to provide at the end of said time interval a signal to said second latch means.

Claim 12

A system for digital weigHing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; a voltage controlled oscillator having an input to be coupled to the output of the load cells to obtain at the output of said oscillator pulses with a frequency proportional to the voltage at its input; an up-down counter coupled, when enabled, to the output of said oscillator; counter control logic means having a first input to receive a pulse for a thermal zero cycle of operation and a second input to receive a pulse for a weigh cycle of operation, coupled to said switch to turn off said switch when a pulse is received by said first input of said logic means and to turn on said switch if necessary when a pulse is received by said second input of said logic means, and coupled to said counter to reset it, to set its count mode and to be signaled by said counter when it reaches zero in a down count; a clock coupled to said logic means to provide a signal to it to start a cycle of operation of it after said logic means receives a pulse at one of said inputs and to provide after a predetermined period of time a second signal to said logic means; first and second latch means coupled, when enabled, to be reset and then set with the final count of said counter at the end of said time interval for the weigh cycle and for the thermal zero cycle, respectively; latch commands coupled to said logic means and to said first and second latch means to enable selectively said first or second latch means to be reset and then set to said final count of said counter for a weigh cycle or a thermal zero cycle, respectively, when said latch commands is signaled by said logic means; and a multiplexer coupled to said second latch means, to said logic means and to said counter to set said counter to the digital value of said latch means after resetting of said counter when said logic means is initiated in its weigh cycle of operation by a signal to its said second input, said logic means when initiated for a weigh cycle or a thermal zero cycle resetting and enabling said counter for the start of said time interval, changing said counter at the start to a down count mode for a weigh cycle, changing the mode of said counter to the up count mode when said counter provides said signal upon reaching zero in the down count, gating closed said counter to cease counting of pulses when said logic means receives said second pulse from said clock, and signaling said latch commands selectively to reset and enable said first and second latch means at the conclusion of said time interval.

Claim 13

A system for digital weigHing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; a voltage controlled oscillator having an input to be coupled to the output of the load cells to obtain at the output of said oscillator pulses with a frequency proportional to the voltage at its input; an up-down counter coupled, when enabled, to the output of said oscillator; counter control logic means having a first input to receive a pulse for a thermal zero cycle of operation and a second input to receive a pulse for a weigh cycle of operation, coupled to said switch to turn off said switch when a pulse is received by said first input of said logic means and to turn on said switch if necessary when a pulse is received by said second input of said logic means, and coupled to said counter to reset it, to set its count mode and to be signaled by said counter when it reaches zero in a down count; a clock coupled to said logic means to provide a signal to it to start a cycle of operation of it after said logic means receives a pulse at one of said inputs and to provide after a predetermined period of time a second signal to said logic means; first and second latch means coupled, when enabled, to be reset and then set with the final count of said counter at the end of said time interval for the weigh cycle and for the thermal zero cycle, respectively; latch commands coupled to said logic means and to said first and second latch means to enable selectively said first or second latch means to be reset and then set to said final count of said counter for a weigh cycle or a thermal zero cycle, respectively, when said latch commands is signaled by said logic means; and a multiplexer coupled to said second latch means, to said logic means and to said counter to set said counter to the digital value of said latch means after resetting of said counter when said logic means is initiated in its weigh cycle of operation by a signal to its said second input, said logic means when initiated for a weigh cycle or a thermal zero cycle resetting and enabling said counter for the start of said time interval, changing said counter at the start to a down count mode for a weigh cycle, changing the mode of said counter to the up count mode when said counter provides said signal upon reaching zero in the down count, gating closed said counter to cease counting of pulses when said logic means receives said second pulse from said clock, and signaling said latch commands selectively to reset and enable said first and second latch means at the conclusion of said time interval.

Claim 17

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; means to turn on and turn off said switch; means operative when said switch is off and when coupled to the output of the load cells to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells; an analog-to-digital converter; means operative, with said switch on, for a weigh cycle of operation of the system to couple said converter to the output of the load cells for at least part of an operation of said converter, so as to generate a digital output from analog voltage output of the load cells due at least in part to the weight affecting the cells; means operative, with said switch on, for a dead load zero cycle of operation of the system to couple said converter to the output of the load cells for at least part of an operation of said converter so as to generate and store a digital output from a voltage input to said analog-to-digital converter obtainable when no load is present to be weighed by the system; means to utilize said stored signal in said converter during a part only of the operation of said converter for a dead load zero cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said thermal voltage of the load cells; means to utilize said stored digital output, obtained by said dead load zero cycle of operation of the system, in said converter during a part only of the operation of said converter for a weigh cycle of operation of the system in a manner to provide a final digital output of said converter that does not include the digital output due to the operation of the converter on an input to said converter representative of any effect other than the weight of the load; and means to utilize said stored signal in said converter during a part only of the operation of said converter for a weigh cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said Thermal voltage of the load cells.

Claim 18

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises: a switch to couple the load cells to a power supply; means to turn on and turn off said switch; means operative when said switch is off and when coupled to the output of the load cells to generate and store a signal having a magnitude based in part on the thermal voltage component only of the voltage output of the load cells; an analog-to-digital converter; means operative, with said switch on, for a weigh cycle of operation of the system to couple said converter to the output of the load cells for at least part of an operation of said converter, so as to generate a digital output from analog voltage output of the load cells due at least in part to the weight affecting the cells; means operative, with said switch on, for a dead load zero cycle of operation of the system to couple said converter to the output of the load cells for at least part of an operation of said converter so as to generate and store a digital output from a voltage input to said analog-to-digital converter obtainable when no load is present to be weighed by the system; means to utilize said stored signal in said converter during a part only of the operation of said converter for a dead load zero cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said thermal voltage of the load cells; means to utilize said stored digital output, obtained by said dead load zero cycle of operation of the system, in said converter during a part only of the operation of said converter for a weigh cycle of operation of the system in a manner to provide a final digital output of said converter that does not include the digital output due to the operation of the converter on an input to said converter representative of any effect other than the weight of the load; and means to utilize said stored signal in said converter during a part only of the operation of said converter for a weigh cycle of operation of the system in a manner to provide a final digital output of said converter essentially devoid of any digital value representative of said Thermal voltage of the load cells.

Claim 19

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises an analog-to-digital converter that includes: a preamplifier having an input to be coupled to the voltage output of the load cells; a first switch; means coupling the output of said preamplifier to said first switch; means to turn on and turn off said first switch; an integrator coupled to said first switch; a comparator coupled to the output of said integrator; a second switch; means coupling said second switch to said integrator to apply through said second switch, when it is on and coupled to a reference voltage of opposite sign to the output voltage of said preamplifier, a voltage to said integrator; means to turn on and turn off said second switch; means to generate pulses at a predetermined frequency; timing means operatively coupled to said means to turn on and turn off said first switch and operatively coupled to said means to turn on and turn off said second switch whereby said timing means, when initiated, turns on said first switch for a predetermined period of time, and then turns off said first switch and turns on said second switch; signal-generating means responsive to the output of said comparator when it crosses zero volts while said second switch is on, to generate a signal; and counter means operatively connected to count pulses from said pulse-generating means when initiated by said timing means until signaled by said signal-generating means to stop counting, said counter means including: up-down decade counters having an up count mode and a down count mode; means responsive to said up-down counters reaching zero in a down count mode; first latches in which are to be entered the final output of said up-down counters obtained by a dead load zero cycle of operation of the system and representing no load on a weighing platform on which the load cells are mounted; second latches in which are to be entered the final output of said up-down counters obtained by a weigh cycle of operation of the system and representing the weight of the load on the platform; a multiplexer coupled to said first latches and to said up-down counters to set, when initiated, said up-down counters to the digital value of said first latches; and counter control logic means being: coupled to said up-down counters, to said first and second latches, to said multiplexer, and to said pulse-generating means, to provide a dead load zero cycle by a sequence of operation or to provide a weigh cycle by different sequence of operation; initiated in its operation of either cycle by said timing means to reset said up-down counters at the end of said predetermined period of time and then to transmit pulses from said pulse-generating means to said up-down counters; responsive to said signal-generating means to cease the transmission of said pulses to said up-down counters; responsive to a pulse to initiate a dead load zero cycle of operation of said logic means to reset said first latches and then in response to the signal from said signal-generating means to trigger said first latches to enter in them the output of said up-down counters; and responsive to a pulse to initiate a weigh cycle of operation of said logic means to reset said second latches, to enable said multiplexer to enter in said up-down counters the digital values in said first latches, to enable said up-down counters in the down count mode, in response to the output of said up-down counters reaches zero in the down count mode to change said up-down counters to the up count mode, and in response to the signal from said signal-generating means to trigger said second latches to enter in them the output of said up-down counters to complete the weigh cycle.

Claim 20

A system for digital weighing by utilizing an analog voltage of load cells generated in part by a load to be weighed, which comprises an analog-to-digital converter that includes: a preamplifier having an input to be coupled to the voltage output of the load cells; a first switch; means coupling the output of said preamplifier to said first switch; means to turn on and turn off said first switch; an integrator coupled to said first switch; a comparator coupled to the output of said integrator; a second switch; means coupling said second switch to said integrator to apply through said second switch, when it is on and coupled to a reference voltage of opposite sign to the output voltage of said preamplifier, a voltage to said integrator; means to turn on and turn off said second switch; means to generate pulses at a predetermined frequency; timing means operatively coupled to said means to turn on and turn off said first switch and operatively coupled to said means to turn on and turn off said second switch whereby said timing means, when initiated, turns on said first switch for a predetermined period of time, and then turns off said first switch and turns on said second switch; signal-generating means responsive to the output of said comparator when it crosses zero volts while said second switch is on, to generate a signal; and counter means operatively connected to count pulses from said pulse-generating means when initiated by said timing means until signaled by said signal-generating means to stop counting, said counter means including: up-down decade counters having an up count mode and a down count mode; means responsive to said up-down counters reaching zero in a down count mode; first latches in which are to be entered the final output of said up-down counters obtained by a dead load zero cycle of operation of the system and representing no load on a weighing platform on which the load cells are mounted; second latches in which are to be entered the final output of said up-down counters obtained by a weigh cycle of operation of the system and representing the weight of the load on the platform; a multiplexer coupled to said first latches and to said up-down counters to set, when initiated, said up-down counters to the digital value of said first latches; and counter control logic means being: coupled to said up-down counters, to said first and second latches, to said multiplexer, and to said pulse-generating means, to provide a dead load zero cycle by a sequence of operation or to provide a weigh cycle by different sequence of operation; initiated in its operation of either cycle by said timing means to reset said up-down counters at the end of said predetermined period of time and then to transmit pulses from said pulse-generating means to said up-down counters; responsive to said signal-generating means to cease the transmission of said pulses to said up-down counters; responsive to a pulse to initiate a dead load zero cycle of operation of said logic means to reset said first latches and then in response to the signal from said signal-generating means to trigger said first latches to enter in them the output of said up-down counters; and responsive to a pulse to initiate a weigh cycle of operation of said logic means to reset said second latches, to enable said multiplexer to enter in said up-down counters the digital values in said first latches, to enable said up-down counters in the down count mode, in response to the output of said up-down counters reaches zero in the down count mode to change said up-down counters to the up count mode, and in response to the signal from said signal-generating means to trigger said second latches to enter in them the output of said up-down counters to complete the weigh cycle.