Measurement instrument and method

Abstract

A measurement instrument having a processor, a first sensor and a second sensor. The processor is adapted to output a measurement signal embodying a measurement of a physical quantity. The first sensor and second sensor are connected to the processor and are operable to generate respectively first and second measurements of the physical quantity. The processor defines a first measurement range within which the measurement signal is dependent on the first measurement and not the second measurement. The processor defines a second measurement range within which the measurement signal is dependent on the second measurement and not the first measurement. The first and second ranges meet at a predetermined transition. The first and second measurements are different at the transition and the measurement embodied in the measurement signal crosses the transition without an abrupt change.

What is claimed is: 
     
         1 . An apparatus comprising:
 a housing; and   a multi-sensor disposed within the housing, the multi-sensor including
 at least two sensors each being configured to generate a respective measurement signal of a physical characteristic over a respective one of a first measurement range and a second measurement range, and 
 a processor connected to the at least two sensors and defining the first and second measurement ranges so that the first and second measurement ranges meet at a predetermined transition where a measurement embodied in the respective measurement signals transitions between the first and second measurement ranges without an abrupt change, the respective measurement signals being different at the predetermined transition. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the predetermined transition for a rising physical characteristic occurs at a higher measurement value than the predetermined transition for a falling physical characteristic. 
     
     
         3 . The apparatus of  claim 1 , wherein the measurement embodied in the respective measurement signal for the first measurement range is adjusted relative to the measurement embodiment in the respective measurement signal for the second measurement range, over at least a portion of the second measurement range, so that a measurement indicated by the apparatus does not change abruptly when crossing the predetermined transition from the first measurement range to the second measurement range. 
     
     
         4 . The apparatus of  claim 1 , wherein the physical characteristic is a pressure. 
     
     
         5 . The apparatus of  claim 1 , wherein the physical characteristic is a gas density. 
     
     
         6 . The apparatus of  claim 1 , wherein the measurement embodied in the respective measurement signal for a first sensor of the at least two sensors is substantially equal to a measurement of the first sensor over at least a portion of the first range and the measurement embodied in the respective measurement signal for a second sensor of the at least two sensors is substantially equal to a measurement of the second sensor over at least a portion of the second range. 
     
     
         7 . The apparatus of  claim 1 , wherein one of the at least two sensors is selected from at least one of a piezo-resistive diaphragm sensor, a heat loss sensor and an ionization sensor. 
     
     
         8 . An apparatus comprising:
 a housing; and   a multi-sensor disposed within the housing, the multi-sensor including
 at least two sensors each being configured to generate a respective measurement signal of a physical characteristic over a respective one of a first measurement range and a second measurement range, and 
 a pressure indicator connected to the at least two sensors, the pressure indictor including a processor configured to provide an indication of a measurement embodied in the respective measurement signals that transitions between the first and second measurement ranges as a substantially continuous function over the first and second measurement ranges, the respective measurement signals being different at the transition. 
   
     
     
         9 . The apparatus of  claim 8 , wherein the transition for a rising physical characteristic occurs at a higher measurement value than the transition for a falling physical characteristic. 
     
     
         10 . The apparatus of  claim 8 , wherein the processor is configured to determine the physical characteristic from but one of the at least two sensors throughout a combined measurement range of the at least two sensors. 
     
     
         11 . The apparatus of  claim 8 , wherein a first sensor of the at least two sensors is configured to provide a first pressure reading and the pressure indicator is configured to indicate a pressure that is substantially equal to the first pressure reading when the first pressure reading is above a selectable predetermined pressure value. 
     
     
         12 . The apparatus of  claim 11 , wherein a second sensor of the at least two sensors is configured to provide a second pressure reading and the pressure indicator is configured to indicate a pressure that is substantially equal to the second pressure reading when the first pressure reading is less than a second predetermined pressure value lower than the selectable predetermined pressure value. 
     
     
         13 . The apparatus of  claim 12 , wherein the second predetermined pressure value is selectable from a number of different predetermined pressure values, and wherein the pressure indicator has a selector for selecting the selectable predetermined pressure value and the second predetermined pressure value. 
     
     
         14 . The apparatus of  claim 12 , wherein the pressure indicator is configured to indicate pressure as a continuously differentiable function over a range that includes a threshold for the second predetermined pressure value. 
     
     
         15 . The apparatus of  claim 14 , wherein the indicated pressure is without an inflection point between the selectable predetermined pressure value and the second predetermined pressure value. 
     
     
         16 . A method comprising:
 producing a first and second reading of a quantifiable physical property with a respective one of a first and second sensors;   selecting, with a processor connected to the first and second sensors, a transition magnitude between a first range corresponding to the first reading and a second range corresponding to the second reading, where the transition magnitude of a rising quantifiable physical characteristic occurs at a higher magnitude of the quantifiable physical property than the transition for a falling physical characteristic; and   adjusting the magnitude of the quantifiable physical property in at least one of the first and second ranges so an indication of the quantifiable physical property transitions between the first and second ranges without an abrupt change where the first and second readings are different at the transition.   
     
     
         17 . The method of  claim 16 , further comprising indicating a magnitude of the quantifiable physical property with the processor such that the indicated magnitude is adjusted only in the second range when the quantifiable physical property is falling. 
     
     
         18 . The method of  claim 16 , further comprising indicating a magnitude of the quantifiable physical property with the processor such that the indicated magnitude is adjusted only in the first range when the quantifiable physical property is rising.