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Patent Issued for Method for Accurately Acquiring Multiple Analog Input Signals, Analog Input Circuit, and Measuring Sensor and Measuring Transducer...

May 7, 2014



Patent Issued for Method for Accurately Acquiring Multiple Analog Input Signals, Analog Input Circuit, and Measuring Sensor and Measuring Transducer Having an Analog Input Circuit of This Type

By a News Reporter-Staff News Editor at Electronics Newsweekly -- Siemens Aktiengesellschaft (Munich, DE) has been issued patent number 8706444, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Bauer, Daniel (Waldbronn, DE); Chemisky, Eric (Soultz sous forets, FR); Eckthaler, Sabine (Rheinzabern, DE); Geppert, Michael (Ottersweier, DE); Hahn, Ulrich (Lebach, DE); Pramanik, Robin (Karlsruhe, DE); Rohrbach, Simon (Karlsruhe, DE); Schmith, Peter (Karlsruhe, DE); Schulmeister, Kurt (Gaggenau, DE); Spatz, Martin (Landau, DE); Walter, Ralf (Waghausel, DE).

This patent was filed on December 18, 2008 and was published online on April 22, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Field of the Invention

"The invention relates to monitoring systems and, more particularly, to a method for accurately acquiring multiple analog input signals which are converted using first and second A/D converters into corresponding digital single measured values.

"The invention also relates to an analog input circuit having electrical inputs for multiple analogue input signals, comprising a measured value output for outputting corresponding measured values and comprising a messaging output for outputting a message, such as an error or warning message. The analog input circuit comprises a higher-order control unit, two A/D converters and at least one preceding activatable multiplexer for switching at least some of the input signals to the respective A/D converter using the control unit.

"The invention additionally relates to a measuring sensor and a measuring transducer, in particular for operation at a two-core current loop. The measuring sensor and the measuring transducer each comprise multiple sensor units for acquiring physical measured quantities, such as pressure, force or temperature, and at least one analog input circuit of this type for acquiring corresponding analog input signals originating from the respective sensor units.

"The analog input signals can in principle originate from any signal sources, such as from a measuring sensor or an audio or video source.

"The focus of the present application are methods in which physical quantities, such as pressure, temperature, force flow, are acquired as measured quantities. The measured quantities typically originate from sensor units, such as from a pressure, temperature, force or flow sensor. The sensor units can be integrated for example in a measuring sensor or in a measuring transducer or be connected thereto. A measuring transducer is a field device which is typically used in plant and automation engineering, such as in the chemical industry, petrochemistry and/or in mining. Measuring transducers of this kind, such as the SITRANS P model manufactured by Siemens, are operated to transmit a measured value to a two-core current loop. The measuring transducer is also supplied with electrical power to energize the electronic circuits by the same two-core current loop.

"Measuring sensors and measuring transducers of this type conventionally comprise one or more analog input circuit(s) which take(s) the measurements using appropriate measuring methods. For this purpose, the analog input circuits comprise one or more analog/digital (A/D) converters. The A/D convertors convert an applied analog input signal or measuring signal into a corresponding digital measured value. The accuracy of an input signal that is to be acquired can be increased by averaging multiple single measured values. If acquisition of multiple input signals is envisaged then an analog multiplexer can be connected upstream of the A/D converter. This analog multiplexer can be activated, for example, by a higher-order control unit, such as a microcontroller, to select the desired measuring channel. Alternatively, the multiplexer can be pre-integrated in the A/D converter. In this case, the A/D converter comprises multiple signal inputs for the analog input signals.

"Highly accurate and at the same time fast measurements are required for the acquisition of the measured quantities mentioned in the introduction with the measuring sensors and measuring transducers, such as for exact control of industrial or chemical processes in the case of a drop in pressure, to be able to quickly intervene in the procedure. Measuring sensors and measuring transducers, of which high operational safety and reliability demands are made in terms of operating safety moreover, also increasingly require certification, such as in accordance with the Safety Integrity Level (SIL) standard to IEC 61508.

"To meet the requirements of this standard, it is known to construct the measuring sensors and measuring transducers in a redundant manner. Drawbacks of this solution are the large space requirement and the high costs due to duplicate or even multiple implementation. Measuring devices are also known which meet the above standard and are also designed so as to be non-redundant. Measuring devices of this type are very expensive, however, because the required A/D converters have to be very fast, secure and at the same time highly accurate. Special A/D converters of this type cost a great deal more than conventional A/D converters, which comparatively are either fast and less accurate or highly accurate and slow. The costs for the special A/D converters are often many times that of commercial A/D converters which are produced in large quantities. It should also be taken into account that the sampling rate is drastically reduced by multiplexing the analog input signals. In the case of conventionally used sigma-delta converters, the sampling rate can even be reduced by a factor 6, even if, for example, two or three input signals are 'multiplexed'. The reason for this is due to the required settling time of the filters in the input circuit of the A/D converters."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "It is therefore an object of the invention to provide a method for accurately acquiring multiple analog input signals and an analog input circuit for performing the method.

"It is further object of the invention is to provide a suitable measuring sensor and a suitable measuring transducer having an analog input circuit of this type.

"These and other objects and advantages are achieved in accordance with invention by a method for accurately acquiring multiple analog input signals which are converted using two A/D convertors into corresponding digital single measured values.

"These and other objects and advantages are achieved in accordance with the invention by a method for accurately acquiring multiple analog input signals which are converted using two A/D converters into corresponding digital single measured values. Here, a first measurement averaging cycle having a predetermined total number of measuring intervals is predetermined by a higher-order control unit. The A/D converters can be switched to at least a part of the input signals using at least one multiplexer, which can be activated by the control unit. Within the first measurement averaging cycle respectively a first input signal is acquired by the first A/D converter in a first number of measuring intervals, which preferably corresponds to the total number, and is cumulatively averaged by the control unit to form a first measured value. A second input signal is acquired by the second A/D converter in a lesser number of measuring intervals than the first number and cumulatively averaged to form a second measured value. The first input signal is acquired by the second A/D converter in a third number of measuring intervals, preferably in only one measuring interval, as at least one further single measured value. A message is output if a deviation of the at least one further single measured value (D1') from the single measured value (D1), which is synchronously acquired by the first A/D converter (2), or from the first measured values (MW1') averaged up to that point exceeds a maximum admissible absolute value of the deviation.

"Due to targeted activation of two 'conventional' A/D converters, comparatively fast, the invention advantageously permits secure and at the same time highly accurate measurement of the analog input signals. For this purpose, a first analog input signal, which requires monitoring, as the carrier of a principal measured quantity, is averaged by one of the two A/D converters in a large number of measuring intervals to form a highly accurate digital measured value.

"This input signal is also simultaneously 'co-measured' once or several times 'in between' by the other of the two A/D converters to check the same two input signals for deviations from each other. As a result, it is advantageously possible to very quickly identify a sudden change in the first sensor signal, such as a pressure value or a flow value in the case of a drop in pressure. A higher-order process-control computer for example can then immediately intervene in the control engineering process.

"In accordance with the invention, it is also possible to immediately determine, from the comparison of the measured values of the two A/D converters, whether an accurate measured value acquisition is still possible within specified tolerance limits. Here, an inadmissible deviation is an accurate indicator of failure or of incorrect operation of one of the two A/D converters. These failures occur in the case of a significant measured value deviation.

"Simultaneous, but extremely improbable, failure of both A/D converters in the sense of a double error will not be considered any further here. If it is also necessary to exclude an error of this kind then, for example, two technically differently designed A/D converters, i.e., from different manufacturers, can be used to drastically reduce the probability of the occurrence of a systematic error. Alternatively or additionally, a third A/D converter can be provided to achieve even greater security in the sense of a 2 out of 3 decision.

"The two A/D converters, which are variable with respect to each other in terms of their accuracy and speed, are for example voltage-frequency (U-f) converters, sigma-delta converters or dual slope converters. The two converters are wired to each other such that they can convert all input signals to be acquired. The wiring can be implemented by a common analog multiplexer. The convertor can be implemented using a respective multiplexer which is connected upstream of an A/D converter. In addition, the multiplexer can be pre-integrated in the A/D converter. Both A/D converters can be integrated in a common electronic component along with the multiplexer. Alternatively, the function of a component of this type can form part of a control unit, such as a microcontroller.

"In an embodiment of the method of the invention, a second measurement averaging cycle having the same total number of measuring intervals is predetermined by the higher-order control unit. Here, the allocation of the A/D converters to the analog input signals is changed after each measurement averaging cycle.

"The advantage of the presently contemplated embodiment of the method of the invention resides in the fact that the A/D converter that is not working correctly can respectively be determined by the control unit. In this case an exact error message can be output to a monitoring device or a computer, for example.

"In accordance with a further embodiment of the method, at least one multiplexer is activated by the higher-order control unit such that, in addition to the second input signal, a third input signal or further input signals are acquired by the respective A/D converter in the remaining measuring intervals of a respective measurement averaging cycle and are cumulatively averaged by the higher-order control unit to form a third measured value or further measured values.

"The third sensor can, for example, be a temperature sensor which can be used to correct the first input signal by compensating for temperature errors. In particular, the third sensor is not used for the acquisition of a principal measured quantity.

"In a further embodiment of the method, at least one calibration cycle is predetermined for the first and second A/D converters by the higher-order control unit after a predetermined number of measurement averaging cycles.

"In an alternative embodiment, a calibration cycle is alternately predetermined by the higher-order control unit for the first or second A/D converter after a predetermined number of measurement averaging cycles.

"An identical total number of measuring intervals, which corresponds to the measurement averaging cycles, is in each case preferably predetermined by the higher-order control unit for a calibration cycle. The calibration cycle or cycles are used to compensate for drifting of the measured values over time, for example, due to temperature effects.

"The object of the invention is also achieved by an analog input circuit having electrical inputs for multiple analog input signals. Here, the input circuit comprises a measured value output for outputting corresponding measured values and a messaging output for outputting a message, i.e., an error message or a signal-change message. The analog input circuit comprises a higher-order control unit, two A/D converters and at least one preceding activatable multiplexer for switching at least a part of the input signals to the respective A/D converter using the control unit. The control unit characteristically comprises a device for performing the method in accordance with the invention and an output device for the measured values and messages.

"An input circuit in accordance with the invention is advantageously configured so as to be redundant only with respect to the measured section from signal input to signal output. A duplicated implementation of the sensor units or measuring points is advantageously omitted. The division into 'nested' cycles means it is possible to achieve monitoring and at the same time avoid losses in speed by dispensing with time-consuming multiplexing within one of these cycles. As a result, it is possible to use inexpensive A/D converters, which it would not be possible to use in independent operation or without the nested cycles.

"The object of the invention is also achieved by a measuring sensor having multiple control units for acquiring physical quantities such as pressure, force, temperature or the like. The measuring sensor comprises at least one inventive analog input circuit for the acquisition of corresponding analog input signals originating from the respective sensor units.

"The object of the invention is additionally achieved by a measuring transducer which is provided in particular for operation at a two-core current loop. The two-core current loop is in particular a standardized 4-20 mA two-core current loop that is common in the industrial sector and in the plant sector. A measuring transducer of this type has multiple sensor units, preferably in integrated form, for acquiring physical quantities such as pressure, force or temperature.

"The measuring transducer comprises at least one analog input circuit in accordance with the invention for acquiring corresponding analog input signals originating from the respective sensor units.

"Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein."

For the URL and additional information on this patent, see: Bauer, Daniel; Chemisky, Eric; Eckthaler, Sabine; Geppert, Michael; Hahn, Ulrich; Pramanik, Robin; Rohrbach, Simon; Schmith, Peter; Schulmeister, Kurt; Spatz, Martin; Walter, Ralf. Method for Accurately Acquiring Multiple Analog Input Signals, Analog Input Circuit, and Measuring Sensor and Measuring Transducer Having an Analog Input Circuit of This Type. U.S. Patent Number 8706444, filed December 18, 2008, and published online on April 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=31&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1537&f=G&l=50&co1=AND&d=PTXT&s1=20140422.PD.&OS=ISD/20140422&RS=ISD/20140422

Keywords for this news article include: Electronics, Engineering, Microcontroller, Siemens Aktiengesellschaft.

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Source: Electronics Newsweekly


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