Thermal recorder for use with battery-powered equipment
First Claim
1. A thermal recorder comprising a thermal print head having a multiplicity of elements for producing dots of heat in response to pulses and a central processing unit programmed to perform the following steps:
- (a) calculating a value corresponding to a pulse width based at least in part on a voltage level being supplied to said thermal print head;
(b) determining the number of elements of said thermal print head to be activated, heating element resistance and print head voltage;
(c) calculating a total current which would be consumed by said elements to be activated with the determined heating element resistance and print head voltage;
(d) acquiring a limit pulse width value corresponding to said calculated total current; and
(e) sending a pulse to each element to be activated, said pulse having a pulse width equal to the lesser of said calculated pulse width value and said limit pulse width value.
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Accused Products
Abstract
A method and an apparatus for limiting the peak power consumed by a thermal recorder connected to portable battery-powered equipment. The battery-powered equipment is designed with a filter and an electronic circuit breaker. A circuit breaker current sense resistor and an output capacitor form an RC filter and provide a large current reservoir for the thermal recorder which averages the peak current demands seen at the circuit input. The electronic circuit breaker provides a current limit function and will not allow a current greater than a predetermined amperage level to be drawn. The thermal recorder has a CPU which provides pulses to a thermal print head in dependence on data incorporated in a pulse-width limit table. The values in the pulse-width limit table can be substituted for calculated pulse widths that would produce peak currents large enough to trip the circuit breaker.
16 Citations
20 Claims
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1. A thermal recorder comprising a thermal print head having a multiplicity of elements for producing dots of heat in response to pulses and a central processing unit programmed to perform the following steps:
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(a) calculating a value corresponding to a pulse width based at least in part on a voltage level being supplied to said thermal print head;
(b) determining the number of elements of said thermal print head to be activated, heating element resistance and print head voltage;
(c) calculating a total current which would be consumed by said elements to be activated with the determined heating element resistance and print head voltage;
(d) acquiring a limit pulse width value corresponding to said calculated total current; and
(e) sending a pulse to each element to be activated, said pulse having a pulse width equal to the lesser of said calculated pulse width value and said limit pulse width value. - View Dependent Claims (2)
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3. A thermal recorder comprising:
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a thermal print head having a multiplicity of elements for producing dots of heat in response to pulses;
means for calculating a value corresponding to a pulse width based at least in part on a voltage level being supplied to said thermal print head;
means for determining the number of elements of said thermal print head to be activated, heating element resistance and print head voltage;
means for calculating a total current which would be consumed by said elements to be activated with the determined heating element resistance and print head voltage;
means for providing a limit pulse width value corresponding to said calculated total current; and
means for pulsing each element to be activated with a pulse having a pulse width equal to the lesser of said calculated pulse width value and said limit pulse width value. - View Dependent Claims (4)
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5. A method of thermal recording, comprising the steps of:
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(a) placing a substrate in opposition to a thermal print head having a multiplicity of elements for producing dots of heat;
(b) calculating a value corresponding to a pulse width based at least in part on a voltage level being supplied to said thermal print head;
(c) determining the number of thermal print head elements to be activated, heating element resistance and print head voltage;
(d) calculating a total current which would be consume d by said elements to be activated with the determined heating element resistance and print head voltage;
(e) determining a limit pulse width value corresponding to said calculated total current; and
(f) sending a pulse to each element to be activated, said pulse having a pulse width equal to the lesser of said calculated pulse width value and said limit pulse width value.
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6. A system comprising a data acquisition subsystem, a thermal print head having a multiplicity of elements, a processing subsystem coupled to receive acquired data from said data acquisition subsystem and send said acquired data to said thermal print head for printing, and a battery, said processing subsystem, said data acquisition subsystem and said thermal print head being powered by said battery in a battery power mode, wherein s aid processing subsystem is programmed to perform the following steps:
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(a) calculating a value corresponding to a pulse width based at least in part on a voltage level being supplied to said thermal print head by said battery;
(b) determining the number of elements of said thermal print head to be activated, heating element resistance and print head voltage;
(c) calculating a total current which would be consumed by said elements to be activated with the determined heating element resistance and print head voltage;
(d) acquiring a limit pulse width value corresponding to said calculated total current; and
(e) sending a pulse to each element to be activated, said pulse having a pulse width equal to the lesser of said calculated pulse width value and said limit pulse width value. - View Dependent Claims (7, 8, 9, 10, 11)
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- 12. A system comprising a portable instrument and a thermal recorder coupled to said portable instrument, wherein said thermal recorder comprises a thermal print head having a multiplicity of elements for producing dots of heat in response to a pulse having a pulse width, and said portable instrument comprises a data acquisition subsystem, a processing subsystem coupled to receive acquired data from said data acquisition subsystem and send acquired data to said thermal recorder for printing, a battery for powering said processing subsystem, said data acquisition subsystem and said thermal print head in a battery power mode, and an electronic circuit breaker through which current passes from said battery to said thermal print head in said battery power mode, wherein said thermal recorder comprises a pulse-width limiting system which limits said pulse width to prevent tripping of said electronic circuit breaker.
- 17. A system comprising a patient monitor and a thermal recorder coupled to said patient monitor, said patient monitor comprising an electronic circuit breaker and a battery, wherein said thermal recorder comprises a thermal print head having a multiplicity of elements for producing dots of heat in response to a pulse having a pulse width, said thermal print head being powered by said battery via said electronic circuit breaker in a battery power mode, wherein said thermal recorder comprises a pulse-width limiting system which limits said pulse width to prevent tripping of said electronic circuit breaker during powering of said thermal print head.
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20. A method for thermal recording of data acquired by a battery-powered patient monitor having an electronic circuit breaker, comprising the steps of:
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(a) placing a substrate in opposition to a thermal print head having a multiplicity of elements for producing dots of heat;
(b) calculating a value corresponding to a pulse width based at least in part on a voltage level being supplied to said thermal print head by a battery;
(c) determining the number of thermal print head elements to be activated, heating element resistance and print head voltage;
(d) calculating a total current which would be consumed by said elements to be activated with the determined heating element resistance and print head voltage;
(e) determining a limit pulse width value corresponding to said calculated total current, said limit pulse width value being set so that the electronic circuit breaker will not trip when said calculated total current is consumed; and
(f) sending a pulse to each element to be activated, said pulse having a pulse width equal to the lesser of said calculated pulse width value and said limit pulse width value.
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Specification