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Field device having an analog output

A technology of analog output and field equipment, applied in the field of measurement converters, can solve the problems that the signal frequency cannot be arbitrarily increased, the signal frequency cannot be arbitrarily reduced, the microcontroller affects power consumption, etc., and the effect of improving the measurement accuracy is achieved.

Inactive Publication Date: 2010-08-18
SIEMENS AG
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The synchronization of the microcontroller directly affects its power consumption and cannot be arbitrarily increased
On the other hand, the frequency of the pulse width modulated signal cannot be reduced arbitrarily in order to achieve a higher bit resolution, since it is a decisive factor for the dynamic behavior of the generated analog output signal

Method used

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  • Field device having an analog output

Examples

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Embodiment Construction

[0018] according to figure 1 , a measuring transducer 1 for detecting a physical or chemical quantity X of a process has a receiver 2 which converts the quantity into a measurement signal 3 . This measurement signal 3 is amplified and digitized in a preprocessing stage 4 . The measurement signals preprocessed in this way are supplied in digital form to the microcontroller 5 , which, for example, performs compensation for non-linearities and temperature influences and calculates the measured values ​​to be output. In the digital / analog converter 6, the digital measured value determined in the microcontroller 5 is converted into an analog output signal, which is output via a 4-20mA interface 7 for further use in process technology devices, in which A measuring transducer 1 is used in the device.

[0019] For digital / analog-conversion, the microcontroller μC is based on figure 2 Generate three time signal PWM 1 , PWM 2 and PWM 3 . Time signal PWM 1 and PWM 2 Calculated ...

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Abstract

The invention relates to a field device having an analog output, especially a measuring transducer (1) for process instrumentation having a 4-20 mA interface as the analog output (7). For digital-to-analog conversion, a digital value is split into a digital coarse portion and a digital fine portion. Depending on the digital coarse portion, a first analog signal (V1) is generated using a pulse width modulator (BUF1) having a low path filter (TP1) mounted downstream thereof, which signal is above the analog output signal (VOUT), and a second output signal (V2) using a pulse width modulator (BUF2) having a low path filter (TP2) mounted downstream thereof, which signal is below the analog output signal(VOUT). Both analog signals (V1, V2) are guided to a third pulse width modulator (SW1) which is controlled depending on the digital fine portion, a low-pass filter (TP3) being mounted downstream thereof. The invention allows provision of an analog output signal (VOUT) having high resolution and good dynamic properties. The field device is further characterized by a digital-to-analog converter that can be produced with especially little complication.

Description

technical field [0001] The invention relates to a field device with an analog output according to the preamble of claim 1, in particular a measuring transducer for a measuring instrument for a production process, which has a 4-20mA interface as an analog output . Background technique [0002] Such a field device is known, for example, from DE 19930661 A1. Measuring transducers with a 4-20 mA connection are used in process measuring instruments for the various measurement of physical or chemical quantities such as pressure, temperature or pH-value. These measuring transducers usually have sensors, the sensor signals of which are amplified, digitized, and then evaluated in a microcontroller and corrected for linearity and temperature behavior. The sensor signal provided in this way is converted into an analog output signal in an output circuit with a digital / analog converter, here an output current in the range of 4-20 mA, and is transmitted via a two-wire cable to an evalua...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01D3/024G08C19/02H03M1/00H03M1/68H03M1/86G08C13/02
CPCH03M1/68G01D3/024H03M1/822
Inventor 埃里克·谢米斯凯迈克尔·格佩特乌尔里希·哈恩西蒙·罗尔巴赫
Owner SIEMENS AG
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