Data processing: measuring – calibrating – or testing – Measurement system – Temperature measuring system
Reexamination Certificate
1999-05-28
2001-02-13
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Temperature measuring system
C702S198000, C340S870210, C341S106000
Reexamination Certificate
active
06188971
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to systems and methods for converting a measurement into engineering units. More particularly, the present invention relates to systems and methods for employing fast techniques of converting analog measurements to engineering units.
2. Related Art
A. General
Many devices depend on measuring a physical quantity, such as temperature or torque, and converting this quantity into a known engineering unit, such as Fahrenheit or Foot Pounds.
Typically, a first step in a conversion process is a transducer. In a typical application, the transducer changes a physical quantity, such as temperature or torque, into a linear or nonlinear proportional voltage. This value is known as an analog voltage that can have any value within a given range.
The transducer is normally interfaced with an analog-to-digital converter, which changes the analog voltage to a digital voltage. The digital voltage can then be expressed as a digital representation of the analog voltage.
In order to be valuable to a user for analysis, most measurements of physical quantities must appear in an engineering units format. Thus, after the analog-to-digital conversion, the resulting data must be converted from a digital value into an engineering unit format. This conversion process, termed engineering unit conversion, is accomplished by interfacing the analog-to-digital converter to a data-acquisition system, which gathers all digital data coming from the analog-to-digital converter. The data acquisition system then applies data to a stored program involving software. The data is then completely evaluated in software by a mathematical equation.
However, these mathematical equations often involve complex polynomial equations increasing computation time and complexity of the data acquisition system. At higher rates of conversion, it becomes impractical to convert voltage measurements of physical quantities, into engineering units. For instance, in a system in which events are represented or acted upon as they occur—“real time”—it is impractical to convert a voltage measurement into engineering units using the above technique of evaluating mathematical formulas at the time of measurement. In such cases, the measurement rate may exceed the ability of the measurement hardware to convert into engineering units. Therefore, measurement quantities are usually recorded in their voltage format, then converted later during a separate data analysis phase.
What is needed is a system and method that obtains engineering units in “real time”. In other words, there is a need for a data acquisition device that can perform the entire data gathering process, as well as, the conversion process in “real time.”
It is presently possible to perform this conversion in “real time” utilizing very high speed computing devices. However, the cost of employing such devices is prohibitive. Therefore, there is also a need for a device that can perform “real time” conversion at a dramatically smaller cost than is presently possible.
B. Thermocouples
One application of the conversion process mentioned above, involves measuring temperature via a thermocouple device. Thermocouples utilize two dissimilar wires bonded together that are applied to a point where a temperature is to be measured. A temperature gradient along those wires causes a thermoelectric effect generating a voltage across the two wires. This voltage may then be applied to an analog-to-digital converter and then data acquisition conversion devices, as discussed above, resulting in an engineering unit, e.g., Fahrenheit. A problem associated with thermocouples is connecting them to a converting device at some intermediate junction with other possibly dissimilar wires. This intermediate junction creates unwanted voltages along these wires due to dissimilar metals and temperatures between the thermocouple device and the converting device. The increased or decreased voltage is thereby transferred to the conversion device, which produces an inaccurate temperature unit reading.
What is needed is a device that obtains engineering units in “real time” and is simultaneously able to compensate for the thermoelectric effect of intermediate wiring junctions relating to thermocouples.
SUMMARY OF THE INVENTION
The present invention relates generally to systems and methods for converting a measurement into engineering units. The present invention includes five embodiments.
According to the first embodiment, the present invention is a system and method for converting an analog measurement into an engineering value. An analog measurement of a physical quantity is transformed into a digital value. The digital value is then split into a high order digit and a lower order digit. The high order digit is used as an address to a memory device for fetching a line segment slope coefficient and a line segment offset coefficient. The lower order digit is multiplied with the line segment slope coefficient in a multiplier resulting in a product. The product is added to the line segment offset coefficient resulting in a sum whose value is an engineering unit.
The second embodiment of the present invention utilizes a re-scaler device for increasing accuracy of the present invention when used with integer or fixed-point digital number formats. An off-line procedure is used to multiply the line segment slope coefficient and the line segment coefficient offset by a pre-scaled coefficient. The re-scaler is used as an offset for correcting for the pre-scaled coefficient.
The third embodiment of the present invention utilizes floating point hardware to compute floating point numerals.
The fourth embodiment of the present invention utilizes parallel memory devices for increasing speed of the system.
According to the fifth embodiment, the present invention is a system for converting a temperature reading to an engineering unit. A thermocouple device is employed for converting the temperature reading to a voltage value. An analog-to-digital converter is then used to convert the voltage value to a digital value. Thereafter, a reference temperature compensation means is utilized to determine an absolute temperature for the reading made by the thermocouple device. This value in turn is then employed as an address means for retrieving slope and offset coefficients from a memory device. A first adder is employed for subtracting the reference coefficient from the digital value resulting in a second digital value having low order bits and high order bits. The above memory device also contains a first coefficient and a second coefficient, whereby the address means is now used for fetching the first coefficient and second coefficient from the memory device. The high order bits are used as an address means for retrieving these coefficients. A multiplier multiplies the lower order bits with the first coefficient fetched from the memory device resulting in a product. Finally, a second adder adds the product from the multiplication operation to the second coefficient fetched from the memory device resulting in an engineering unit.
FEATURES AND ADVANTAGES OF THE INVENTION
One feature of this invention is to provide a fast technique for converting a voltage measurement of a physical quantity into an engineering unit. The present invention is able to perform this conversion process in “real time” for extended periods of time by using a portion of data from an analog-to-digital converter as an address. The present invention is able to function as fast or faster than any existing methods.
Another feature of the present invention is simplicity. Thus, the present invention can be implemented with very simple hardware components making it a far cheaper alternative to other data acquisition devices.
A further feature of the present invention is the ability to simultaneously multiplex several transducers into a data acquisition system and simultaneously perform “real time” conversion. This invention can simultaneously multiplex different transducer types or seve
Agilent Technologie,s Inc.
Hoff Marc S.
Vo Hien
LandOfFree
Fast technique for converting temperature readings into... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fast technique for converting temperature readings into..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fast technique for converting temperature readings into... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2561304