Method and apparatus for measuring temperature
AssigneeWilliam Wahl Corporation
InventorsKenneth G. Junkert, Henry P. Voznick
Life of this patent
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Abstract
Temperature dependent and reference time intervals are simultaneously generated and differentially combined to provide a temperature signal that is employed to generate a probe linearization signal for combination with the temperature signal and digital display. A low resistance platinum probe carries a low current in a timing circuit having a small capacitor charging to a relatively high voltage to provide a high gain for temperature to time conversion circuitry. A continuous real time probe linearization signal is computed for large temperature readings by a double integration circuit having an adjustable readout time for determining the magnitude of the twice integrated temperature signal.
Claims29
A temperature measuring instrument comprising
- first and second resistors,
- first and second slope generators connected with said
- first and second resistors respectively, for generating
- first and second ramp signals, each having a slope
- determined by a corresponding one of said resistors,
- first and second slope to time converters responsive respectively to said first and second ramp signals for generating first and second time intervals respectively indicative of the slopes of said first and second ramp signals,
- timing means for simultaneously repetitively triggering said first and second converters,
- means responsive to said first and second converters for repetitively actuating said first and second slope generators in synchronism with each other,
- means responsive to both said converters for combining the time intervals produced thereby to generate a measurement signal representative of the difference between said first and second time intervals, and
- means for indicating the duration of said measurement signal.
In a thermometer having a resistive sensing element of which the resistance varies with temperature, a gain controlling input circuit comprising
- an amplifier having first and second opposite polarity inputs and an output,
- a source of potential connected to said first input,
- a capacitor connected in a feedback path between said output and said second input,
- means for connecting said resistive sensing element between a second potential and the side of the capacitor connected to said second input to maintain a fixed potential across said resistive sensing element, and
- means for discharging said capacitor at a predetermined voltage.
A thermometer comprising a sensing element having a characteristic that varies as a non-linear function of temperature, means responsive to said sensing element for generating an electrical temperature signal having a duration that varies in linear relation with said characteristic of said sensing element, means responsive to said electrical temperature signal for generating a linearization signal having a duration that varies as a non-linear function of said electrical signal, and means for combining said linearization signal with said electrical temperature signal to provide an output electrical signal representing temperature to which said sensing device is subjected and compensated for the temperature non-linearity of said sensing element.
A thermometer comprising
- a sensing element having a characteristic that varies as a non-linear function of temperature,
- means responsive to said sensing element for generating an electrical temperature signal having a parameter that varies in linear relation with said characteristic of said sensing element,
- means responsive to said electrical temperature signal for generating an analog linearization signal that varies continuously as a non-linear function of said electrical signal,
- means for combining said linearization signal with said electrical temperature signal to provide an output electrical signal representing temperature to which said sensing device is subjected and compensated for the temperature non-linearity of said sensing element, and means for disabling generation of said linearization signal for values of said temperature signal within a selected range of values relative to a reference.
A thermometer comprising
- a sensing element having a characteristic that varies as a non-linear function of temperature,
- means response to said sensing element for generating an electrical temperature signal having a duration that varies in linear relation with said characteristic of said sensing element,
- means responsive to said electrical temperature signal for generating a linearization signal having a duration that varies as a non-linear function of said electrical signal,
- means for combining said linearization signal with said electrical temperature signal to provide an output electrical signal representing temperature to which said sensing device is subjected and compensated for the temperature non-linearity of said sensing element,
- said means for generating said electrical temperature signal comprising means for generating an electrical pulse having a duration representative of the quantity R.sub.O aT + R.sub.O bT.sup.2, where R.sub.O is the resistance of said element at a predetermined temperature, T is temperature, a is a constant representing the linear gain characteristics of said element, and b is a constant representing a second order non-linear gain characteristic of said element, said means for generating said linearization signal comprising means responsive to said pulse for generating a compensatory pulse having a duration representing the quantity R.sub.O bT.sup.2, said means for combining comprising means for generating an output signal having a duration equal to the combined durations of said temperature pulse and said compensatory pulse.
A linear thermometer comprising a resistive sensing element having a resistance R that varies in accordance with the equation R=R.sub.O (1 + aT + bT.sup.2) where R.sub.O is the resistance of said element at a predetermined temperature, T is temperature, a is a constant representing the linear gain characteristics of said element, and b is a constant representing a second order non-linear gain characteristic of said element, means responsive to said sensing element for generating a first temperature signal having a duration representing the difference between R.sub.O and the quantity R.sub.o + aT + R.sub.O bT.sup.2,
- means responsive to said first temperature signal for generating a second temperature signal having a duration representing the quantity R.sub.O bT.sup.2, and means for combining said first and second temperature signals to provide a linearized temperature signal.
A linear thermometer comprising
- a resistive sensing element having a resistance R that varies in accordance with the equation R=R.sub.O (1 + T + bT.sup.2) where r.sub.O the resistance of said element at a predetermined temperature, T is temperature, a is a constant representing the linear gain characteristics of said element, and b is a constant representing a second order non-linear gain characteristic of said element,
- means responsive to said sensing element for generating a first temperature signal representing the difference between R.sub.O and the quantity R.sub.o + R.sub.O aT + R.sub.O bT2,
- means responsive to said first temperature signal for generating a second temperature signal representing the quantity R.sub.O bT.sup.2,
- means for combining said first and second temperature signals to provide a linearized temperature signal, and
- including means for initiating generation of said second temperature signal in response to attainment of a predetermined minimum value by said first temperature signal.
A linear thermometer comprising
- a resistive sensing element having a resistance R that varies in accordance with the equation R=R.sub.0 (1 + aT + bT .sup.2) where R.sub.O is the resistance of said element at a predetermined temperature, T is temperature, a is a constant representing the linear gain characteristics of said element, and b is a constant representing a second order non-linear gain characteristics of said element,
- means responsive to said sensing element for generating a first temperature signal representing the difference between R.sub.O and the quantity R.sub.O + R.sub.O aT + R.sub.O bT.sup.2,
- means responsive to said first temperature signal for generating a second temperature signal representing the quantity R.sub.O bT.sup.2, and
- means for combining said first and second temperature signals to provide a linearized temperature signal, said means for generating said second temperature signal comprising first integrating means for integrating said first temperature signal and providing a first integrated output, and second integrating means for integrating said first integrated output to provide a double integrated output.
The method of measuring temperature comprising
- generating a temperature signal including a non-linear component that varies in a known non-linear relation to temperature,
- generating a linearization signal that varies as said non-linear component,
- combining said temperature and linearization signals, indicating said combined signals for temperatures that differ from a reference temperature by more than a preselected amount, and
- indicating said temperature signal without said linearization signal for temperatures differ differe from said reference by less than said preselected amount.
A linear thermometer comprising a sensing element having a characteristic that includes a first component that varies linearly with temperature and a second component that varies non-linearly with temperature,
- means for generating a temperature signal having a duration representing the difference between a reference and said sensing element characteristic,
- means responsive to said temperature signal for generating a linearization signal having a duration representing said second component, and
- means for combining said temperature and linearization signals.
A temperature measuring instrument comprising
- first and second resistors,
- first and second slope generating circuits connected with said first and second resistors, respectively, for generating first and second ramp signals each having a slope determined by a corresponding one of said resistors,
- first and second slope-to-time converters responsive respectively to said first and second ramp signals for generating first and second time intervals respectively indicative of the slopes of said first and second ramp signals,
- means responsive to both said converters for combining the time intervals produced thereby to generate a measurement signal representative of the difference between said first and second time intervals,
- means for indicating the duration of said measurement signal,
- at least one of said slope generating circuits comprising
- a capacitor,
- said first resistor connected between one side of said capacitor and a point of fixed potential,
- an amplifier having an output and first and second opposite polarity inputs, and having a feedback loop connecting the output of the amplifier with said first input,
- means for connecting said capacitor in said feedback loop,
- means for supplying a selected potential to said second amplifier input, and
- means for discharging said capacitor.
Dependencies are inferred from the claim text.