Back to results
US 5,705,792 AGranted
Digital temperature sensing conditioning and safety system with current control
AssigneeRobertshaw Controls Company
InventorDonald W. Graham
Life of this patent
Estimating the term…
Abstract
A temperature sensing system that includes a temperature probe, a signal conditioning circuit, and a microprocessor. The conditioning circuit incorporates a novel dual voltage range measurement technique that improves the accuracy of such systems. The safety circuitry is provided in order to protect against thermal runaway and to inhibit or enable a door lock.
Claims7
A temperature sensing system, comprising:
- a signal conditioning circuit connected to a temperature sensing probe;
- wherein said signal conditioning circuit creates a first signal to control a heater device in response to an input from said temperature sensing probe based on an external variable temperature measurement;
- a safety circuit connected to said signal conditioning circuit;
- wherein said safety circuit creates a second signal that operates to disable an oven door lock device above a first maximum temperature level and creates a third signal that operates to disable an oven heater device above a second maximum temperature level;
- and,
- a microprocessor connected to said signal conditioning circuit and said safety circuit.
3 more elements
A signal conditioning circuit, comprising:
- a voltage source;
- a first operational amplifier stage connected to said voltage source;
- wherein said first operational amplifier stage is a voltage-to-current converter;
- a temperature sensing probe connected to said first operational amplifier stage;
- wherein said temperature sensing probe further comprises a resistance temperature detector that is located in a feedback loop of said first operational amplifier stage;
- wherein said first operational amplifier stage operates to convert a resistance change of said resistance temperature detector into a proportional first voltage signal;
- and
- a second operational amplifier stage connected to said first operational amplifier stage and a second voltage signal;
- wherein said second operational amplifier stage is a difference amplifier that compares said second voltage signal to said proportional first voltage signal to create an output signal to control an oven heater device;
- wherein said second voltage signal is created by a second voltage source and resistor network voltage divider circuits which include a switch device to divide said second voltage source.
7 more elements
A safety circuit, comprising:
- a first operational amplifier stage connected to a first voltage source;
- wherein said first operational amplifier stage is a comparator that compares said first voltage source to a first voltage signal to create a first digital signal to control an oven door lock device;
- wherein said first voltage signal is created by a resistor network voltage divider circuit which divides a second voltage source;
- and
- a second operational amplifier stage connected to said first voltage source;
- wherein said second operational amplifier stage is a comparator that compares said first voltage source to a second voltage signal to create a second digital signal to control an oven temperature limiting device;
- wherein said second voltage signal is created by dual resistor network voltage divider circuits which include a switch device to select one circuit at a time and divide said second voltage signal.
4 more elements
A method for converting an input temperature signal into output voltage signals, the method comprising:
- receiving an input temperature signal;
- applying said input temperature signal to a temperature sensing probe to create a proportional resistance value in said probe;
- applying said resistance value to a first operational amplifier stage that is a voltage-to-current converter to convert said resistance value into a proportional first voltage signal;
- applying a first voltage source to two resistor network voltage divider circuits which include a first switch device to select one circuit at a time and divide said voltage source signal to create a second voltage signal;
- applying said first voltage signal to a second operational amplifier that is a difference amplifier to convert said first voltage signal into a third voltage signal by comparing said first voltage signal to said second voltage signal;
- processing said third voltage signal into a digital signal to control an oven heater device;
- applying said first voltage signal to a resistor network to create a fourth voltage signal;
- applying said first voltage source to a third operational amplifier stage that compares said first voltage source with said fourth voltage signal to create a fifth voltage signal;
- processing said fifth voltage signal into a digital signal to control an oven door lock device;
- applying said first voltage signal to dual resistor voltage divider circuits which include a second switch device to select one circuit at a time and divide said first voltage signal to create a sixth voltage signal;
- applying said first voltage source to a fourth operational amplifier stage that compares said first voltage source with said sixth voltage signal to create a seventh voltage signal;
- and
- processing said seventh voltage signal into a digital signal to control an oven heater over-temperature limit device.
10 more elements
A temperature sensing system, comprising:
- a temperature sensor, wherein said temperature sensor means is a resistance temperature detector;
- a first operational amplifier connected to said temperature sensor and a first voltage source, wherein said first operational amplifier includes a voltage-to-current converter with an output proportional to the temperature sensor output;
- a second operational amplifier connected to said first operational amplifier, wherein said second operational amplifier converts said first operational amplifier output into a third voltage signal by comparing said first operational amplifier output to a second voltage signal;
- a dual resistor network voltage divider circuit connected to said second operational amplifier, said divider circuit including a first switch for selecting one circuit at a time and dividing said first voltage source to create said second voltage signal;
- a third operational amplifier connected to said first voltage source;
- wherein said third operational amplifier compares said first voltage source with a fourth voltage signal to create a fifth voltage signal;
- wherein said third operational amplifier is connected to a dual resistor network voltage divider circuit for processing said first voltage signal into said fourth voltage signal;
- and
- a fourth operational amplifier connected to said first voltage source;
- wherein said fourth operational amplifier compares said first voltage source with a sixth voltage signal to create a seventh voltage signal;
- wherein said fourth operational amplifier is connected to a dual resistor voltage divider circuit which includes a second switch for selecting one circuit at a time and dividing said first voltage signal to create said sixth voltage signal;
- and
- a processor connected to said second, third and fourth operational amplifier;
- wherein said processor converts said third voltage signal into a first digital signal to control an oven heater and converts said fourth voltage signal into a second digital signal to control an oven door lock, and converts said seventh voltage signal into a third digital signal to control an oven heater over-temperature limit.
11 more elements
Dependencies are inferred from the claim text.