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CN-113765522-B - Circuit for analog-to-digital conversion

CN113765522BCN 113765522 BCN113765522 BCN 113765522BCN-113765522-B

Abstract

A circuit for analog-to-digital conversion is shown, having a first terminal, a second terminal, a third terminal and a fourth terminal, an analog-to-digital converter ADC, a first current source circuit for outputting a first output current, a first switching device for a switchable connection of the first current source circuit to the first terminal or the third terminal, a pull-sink current circuit for outputting a second output current, a second switching device for a switchable connection of the pull-sink current circuit to a reference potential or the second terminal, and a third switching device for a switchable connection of the reference potential to the second terminal or the fourth terminal, the terminals being used for connecting a sensor, a first input of the analog-to-digital converter being connected to the first terminal and a second input of the analog-to-digital converter being connected to the second terminal.

Inventors

  • TORSTEN LINDNER
  • Mathias cluller

Assignees

  • WAGO管理有限责任公司

Dates

Publication Date
20260505
Application Date
20210407
Priority Date
20200605

Claims (18)

  1. 1. A circuit for the analog-to-digital conversion, Having a first terminal (201) and a second terminal (202) and a third terminal (203) and a fourth terminal (204) for connecting to the sensor (140, 150), Having an analog-to-digital converter ADC (300), a first input (301) of which is connected to a first terminal (201) and a second input (302) of which is connected to a second terminal (202), Having a first current source circuit (210) for outputting a first output current I 1 , Having a first switching device (230) for switchably connecting the first current source circuit (210) to the first terminal (201) or the third terminal (203), Having a pull-sink current circuit (220) for outputting a second output current I 2 , Having a second switching device (240) for switchably connecting the pull-in circuit (220) to a reference potential or to a second terminal (202), and Has a third switching device (250) for switchably connecting the reference potential to the second terminal (202) or to the fourth terminal (204).
  2. 2. The circuit for analog-to-digital conversion of claim 1, Wherein the ADC (300) has a third input (303) and a fourth input (304), Wherein the first current source circuit (210) is connected to the first switching device (230) via a resistor (280), Wherein the third input (303) and the fourth input (304) are connected to a resistor (280).
  3. 3. The circuit for analog-to-digital conversion of claim 1, Wherein the first switching means (230) has a leakage current of less than 3 mA.
  4. 4. The circuit for analog-to-digital conversion of claim 1, Wherein the first switching means (230) has a leakage current of less than 30 μΑ.
  5. 5. A circuit for analog to digital conversion according to any one of claims 1 to 4, Wherein the circuit has a control circuit (270) for controlling the switching device (230, 240, 250, 260), wherein the control circuit (270) is designed to switch between a plurality of measurement modes.
  6. 6. The circuit for analog-to-digital conversion of claim 5, Wherein in a first measurement mode, the first switching means (230) conductively connects the first current source circuit (210) with the first terminal (201), Wherein in the first measurement mode, the second switching device (240) conductively connects the pull-up current circuit (220) to a reference potential, and Wherein in the first measurement mode, the third switching means (250) conductively connects a reference potential with the second terminal (202).
  7. 7. The circuit for analog-to-digital conversion of claim 5, Wherein in a second measurement mode, the first switching means (230) conductively connects the first current source circuit (210) with the first terminal (201), Wherein in the second measurement mode, the second switching device (240) conductively connects the pull-in current circuit (220) with the second terminal (202), and Wherein in the second measurement mode, the third switching means (250) conductively connects a reference potential with the fourth terminal (204).
  8. 8. The circuit for analog-to-digital conversion of claim 6, Wherein in a second measurement mode, the first switching means (230) conductively connects the first current source circuit (210) with the first terminal (201), Wherein in the second measurement mode, the second switching device (240) conductively connects the pull-in current circuit (220) with the second terminal (202), and Wherein in the second measurement mode, the third switching means (250) conductively connects a reference potential with the fourth terminal (204).
  9. 9. The circuit for analog-to-digital conversion of claim 5, Wherein in a third measurement mode, the first switching means (230) conductively connects the first current source circuit (210) with the third terminal (203), Wherein in the third measurement mode, the second switching device (240) conductively connects the pull-up current circuit (220) to a reference potential, and Wherein in the third measurement mode, the third switching means (250) conductively connects a reference potential with the fourth terminal (204).
  10. 10. A circuit for analog to digital conversion according to any one of claims 6 to 8, Wherein in a third measurement mode, the first switching means (230) conductively connects the first current source circuit (210) with the third terminal (203), Wherein in the third measurement mode, the second switching device (240) conductively connects the pull-up current circuit (220) to a reference potential, and Wherein in the third measurement mode, the third switching means (250) conductively connects a reference potential with the fourth terminal (204).
  11. 11. The circuit for analog-to-digital conversion of claim 5, Wherein in a fourth measurement mode, the first switching means (230) conductively connects the first current source circuit (210) with the first terminal (201), Wherein in the fourth measurement mode, the second switching device (240) conductively connects the pull-up current circuit (220) to a reference potential, and Wherein in the fourth measurement mode, the third switching means (250) conductively connects a reference potential with the fourth terminal (204).
  12. 12. A circuit for analog to digital conversion according to any one of claims 6 to 9, Wherein in a fourth measurement mode, the first switching means (230) conductively connects the first current source circuit (210) with the first terminal (201), Wherein in the fourth measurement mode, the second switching device (240) conductively connects the pull-up current circuit (220) to a reference potential, and Wherein in the fourth measurement mode, the third switching means (250) conductively connects a reference potential with the fourth terminal (204).
  13. 13. The circuit for analog-to-digital conversion of claim 5, Wherein the ADC (300) has a fifth input (305) and a sixth input (306), and Wherein the fifth input (305) and the sixth input (306) are connected to a measuring resistor (290).
  14. 14. A circuit for analog to digital conversion according to one of claims 6 to 9, 11, Wherein the ADC (300) has a fifth input (305) and a sixth input (306), and Wherein the fifth input (305) and the sixth input (306) are connected to a measuring resistor (290).
  15. 15. The circuit for analog-to-digital conversion of claim 13, Wherein in a fifth measurement mode, the first switching means (230) conductively connects the first current source circuit (210) to a reference potential via a measurement resistor (290), Wherein in the fifth measurement mode, the second switching device (240) connects the pull-sink current circuit (220) in a conductive manner with a reference potential, Wherein in the fifth measurement mode, the third switching means (250) conductively connects a reference potential to the fourth terminal (204), and Wherein the analog-to-digital converter (300) is designed to read in a voltage falling across the measuring resistor (290) via a fifth input (305) and a sixth input (306).
  16. 16. The circuit for analog-to-digital conversion of claim 14, Wherein in a fifth measurement mode, the first switching means (230) conductively connects the first current source circuit (210) to a reference potential via a measurement resistor (290), Wherein in the fifth measurement mode, the second switching device (240) connects the pull-sink current circuit (220) in a conductive manner with a reference potential, Wherein in the fifth measurement mode, the third switching means (250) conductively connects a reference potential to the fourth terminal (204), and Wherein the analog-to-digital converter (300) is designed to read in a voltage falling across the measuring resistor (290) via a fifth input (305) and a sixth input (306).
  17. 17. The circuit for analog to digital conversion according to one of claims 6 to 9, 11, 13, 15 to 16, Has fourth switching means (260) for switchably connecting a constant voltage to the third terminal (203).
  18. 18. The circuit for analog-to-digital conversion of claim 17, Wherein in a sixth measurement mode, the second switching means (240) conductively connects the pull-up current circuit (220) with the second terminal (202), Wherein in the sixth measurement mode, the third switching means (250) conductively connects a reference potential with the fourth terminal (204), Wherein in the sixth measurement mode, the fourth switching means (260) conductively connects a constant voltage with the third terminal (203).

Description

Circuit for analog-to-digital conversion Technical Field The present invention relates to a circuit for analog to digital conversion. More particularly, the present invention relates to a transformer having circuitry for analog to digital conversion. Background The transformer may convert the analog signal into a digital value and map the digital value to a measured value (e.g., a physical parameter) by means of a nonlinear measurement function. Disclosure of Invention The circuit for analog-to-digital conversion according to the invention comprises a first terminal, a second terminal, a third terminal and a fourth terminal, an analog-to-digital converter ADC, a first current source circuit for outputting a first output current, a first switching device for a switchable connection of the first current source circuit to the first terminal or the third terminal, a pull-sink current circuit for outputting a second output current, a second switching device for a switchable connection of the pull-sink current circuit to a reference potential or the second terminal, and a third switching device for a switchable connection of the reference potential to the second terminal or the fourth terminal, the terminals being for connection to a sensor, a first input of the analog-to-digital converter being connected to the first terminal and a second input of the analog-to-digital converter being connected to the second terminal. The term "circuit" as used in the description and in the claims is understood here to mean in particular that the electrical component and the electronic component are coupled in a functional arrangement. For example, the circuit may be part of a transformer that converts the sensor signal into a measurement value. In addition to the circuit according to the invention, the transformer may be provided with a circuit (e.g. with a processor) designed to map the digital value output by the ADC to the measured value based on a non-linear measurement function. The term "processor" used in the present description is understood here to mean, in particular, an electronic circuit which is designed to carry out commands from a command set (assigned to the processor), wherein the order of the commands (and, if appropriate, the arguments assigned to the commands) can be predetermined by a program executed by the processor. Furthermore, the term "nonlinear measurement function" as used in the description is understood to mean, in particular, a nonlinear allocation rule (for example a calculation rule) by means of which measured values can be allocated to digital values. The measured value may for example point to a quantitative description about the physical parameter, such as the temperature level at a specific location. The measured value may be, for example, a digital value, such digital value being provided in digital form by the processor. The circuit (or the transformer when the circuit is a component of the transformer) may be provided in a device. The device may be configured as an input/output module (I/O module). The term "I/O module" used in the context of the present description is understood here to mean, in particular, a module which can be connected in series or already connected to a front end and which connects one or more field devices (for example sensors and/or actuators) to the front end and, if appropriate (via the front end), to a superordinate control system. In this connection, the term "front-end" used in the context of the present description is to be understood as a component of a modular field bus node, which has the task of making available the data and/or services of the modules of the I/O connected in series to the front-end via the field bus connected to the front-end. Furthermore, the term "input" as used in the description and in the claims is to be understood in particular as an electrical terminal through which an electrical signal (for example a voltage value and/or a current value) can be read in (and thus further processed in an ADC). The term "terminal" as used in the description and claims is to be understood here in particular as meaning an electrical contact point (for example a terminal point with an electrical conductor, such as for example a tension spring terminal) which is designed to be connected temporarily or permanently to an electrical conductor (or the electrical conductor). Furthermore, the term "analog-to-digital converter" used in the description and in the claims is understood to mean, in particular, a circuit which determines to which of a plurality of value ranges an analog value belongs and which outputs a digital value corresponding to the respective value range. The digital value may be output as a bit sequence, for example. Furthermore, the concept of a "current source circuit" as used in the description and in the claims is understood in particular to be a circuit which is designed to output a current of a specific intensity. The specific intensit