Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
  • G01D3/00—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups
  • G01D3/028—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure
  • G01D3/032—Indicating or recording apparatus with provision for the special purposes referred to in the subgroups mitigating undesired influences, e.g. temperature, pressure affecting incoming signal, e.g. by averaging; gating undesired signals

Definitions

• the present invention relates to the kind of methods and devices for correcting incorrect signals from sensors described in the preambles of claim 1 and 2 respectively.
• These devices are arranged to correct signals from the sensors, which are arranged to control a process, it being possible to obtain, at the measurings performed by these sensors, the correct measuring values by sampling or by a short utilization of another sensor, e.g. a to ⁇ tally cleaned one.
• this concerns measuring opera ⁇ tions which are possible to perform in a correct way, but which said sensor for different reasons, e.g. con ⁇ tamination, wear and the like, is not capable to perform in an acceptable way without correcting the given signals which are intended to control a certain process.
• the sen ⁇ sor will of course present the correct measuring values and deliver the correct control signals when it is put in use for the first time, but here processes are concerne in which the sensor must be placed in an environment which relatively fast changes the properties of the sensor and influences the obtained measuring result.
• the device is thus intended to be placed adjacent to the place where samples of the measured medium are taken or where evalu ⁇ ation of the same is done.
• Sensors which are arranged to give signals for control ⁇ ling a certain part of a process or the whole process by measuring one or several parameters of the process and are subject to changes in the lapse of time, will not be able to control the process in a satisfactory way, even if samplings for determination of the correct values of said parameters are performed relatively often.
• the incorrect signals from the sensors will require adjus ⁇ ting of different set points of a regulator to be performed after each sampling, and the sensor cannot control the process in a reliable way even between said samplings.
• the object of the present invention is to provide a method and a device of the kind defined in the preambles of claim 1 and 2 respectively, which in an uncomplicated and reliab way enable a correction of incorrect signals delivered by a sensor for controlling a process.
• fig 1 is a diagram illustrating how the correction cons ⁇ tants, stored in a memory, are interpolated to a straight line, according to which the correction is made, and
• fig 2 is a very diagrammatic representation illustrating the parts included in the correction device.
• the correction is intended to take place by letting a person take a sample of the measured medium (or make a determination of the same) and on that occasion push one of the buttons of the device, here mentioned "sample taken”.
• the device then will measure, via the signal cable connected to the device, the signal from the sensor a number of times determined at the starting of the device, and with time inerval determined at the starting. These measurements are stored in the Random Access Memory (RAM) of the device. From these measured signals from the sensor the highest and the lowest result will be ignored and from the rest an average is formed and stored in the memor of the device. When the analysis-/determination result is ready this is fed into the correction device.
• RAM Random Access Memory
• the correction constant is the number by which the input signal is to be multiplied if the sensor should show a value corresponding to the lab sample-/determination.
• the Y-axis in the diagram of fig 1 indicates the value of the calculated correction constants
• the X-axis is a time axis, the markings of which are indicating the moments of sampling.
• a straight line (fig 1) is calculated by means of "the me ⁇ thod of least squares" and as correction term the value which the Y-co-ordinate obtains for the line at the value on the X-axis is used (10), which is defined at the po ⁇ sition for the youngest value (11).
• the input signal is multiplied with the correction term and is in a corrected condition sent further to the regu ⁇ lator, indicating instrument or the like.
• the unique and new with this type of correction is prin ⁇ cipally:
• That the device may be placed at the location for the sampling or the determination of the measured medium, which enables reading of the measuring signal in close vicinity of the sampling and errors arising in the time delay between the sampling and the reading of the sensor are eliminated.
• That the device offers automatic calibration of the sen ⁇ sor without personnel qualified in instrument technique.
• the correction device is constituted by modules according to fig 2 and comprises the following in its apparatus box:
• CPU-module (20) comprises microprocessor and RAM
• Memory module (21) comprises ROM with program to perform the correction.
• A/D-module (22) receives the signal from the sensor and transduces it into digital infor ⁇ mation via a 14 bits A/D-transducer.
• D/A-modul (23 transduces the calculated, corrected signal to a current or voltage signal. It comprises a relay, which in closed condition makes it possible to correct the signal and in not closed condition connects the input and output signal leads.
• the relay is pulling when all the necessary parameters have been put in at the starting. If the voltage to the device disappears or if the internal samplings are detec ⁇ ting errors, the relay is set free.
• Voltage mo ⁇ supplies the electronics with necessary dule (27) voltages, 5V, 12V and 80V alternating voltage for illumination of the displa
• Back plane constitutes the connection between module (26) the CPU module and the memory module.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Control By Computers (AREA)
• Indication And Recording Devices For Special Purposes And Tariff Metering Devices (AREA)
• Testing Or Calibration Of Command Recording Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20363588

Family Applications (1)

Country Status (2)

Citations (4)

• 1986
  • 1986-02-26 SE SE8600849A patent/SE452058B/sv not_active IP Right Cessation
• 1987
  • 1987-02-23 WO PCT/SE1987/000088 patent/WO1987005388A1/en unknown

Patent Citations (4)

Non-Patent Citations (1)

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