Two-Wire Sensor Current Loop for High Peak Current Operation
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Solution Overview
Problem
Existing sensor devices requiring high peak current face limitations in two-wire current loops, as they cannot draw more than 4 mA, leading to inefficiencies and inability to differentiate sensor readings from current draw, especially in systems like Building Automation Systems.
Innovation Solution
A two-wire sensing unit with a regulator to limit input current to 4 mA, an energy storage unit to store excess power, a DC-DC conversion unit to reduce voltage for the sensor, and a current conversion unit to manage output current, ensuring continuous operation and readable data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a sensor draws more than 4 mA through the power-supply wire to meet high peak current requirements, then the sensor can operate with sufficient power, but more than 4 mA must be outputted through the reading-output wire which causes the output signal to be unable to differentiate sensor readings from current draw
Solution Approach 1:
The patent segments the current path into two independent paths: a power path through the power-supply wire and a signal path through the reading-output wire. The shunt regulator creates a separate power dissipation path that allows the sensor to draw high current (e.g., 20 mA) through the power wire while only 4 mA flows through the reading-output wire. This segmentation enables the signal path to maintain the required 4-20 mA output range for Building Automation Systems while the power path handles the high current draw through the shunt regulator's controlled dissipation.
Solution Approach 2:
The shunt regulator acts as an intermediary component between the power-supply wire and the reading-output wire. It controls the current distribution by shunting excess current to ground, allowing the sensor to receive high current while the reading-output wire maintains a controlled 4 mA minimum current. This intermediary device resolves the conflict between high power requirements and signal integrity by mediating the current flow between the two wires.
2Loss of information
If a sensor is limited to drawing only 4 mA from the power supply in a two-wire configuration, then the reading output can differentiate sensor readings from current draw, but the sensor cannot obtain sufficient power for high peak current operations
Solution Approach 1:
The patent segments the current path into two independent paths: a power path through the power-supply wire and a signal path through the reading-output wire. The shunt regulator creates a separate power dissipation path that allows the sensor to draw high current (e.g., 20 mA) through the power wire while only 4 mA flows through the reading-output wire. This segmentation enables the signal path to maintain the required 4-20 mA output range for Building Automation Systems while the power path handles the high current draw through the shunt regulator's controlled dissipation.
Solution Approach 2:
The shunt regulator acts as an intermediary component between the power-supply wire and the reading-output wire. It controls the current distribution by shunting excess current to ground, allowing the sensor to receive high current while the reading-output wire maintains a controlled 4 mA minimum current. This intermediary device resolves the conflict between high power requirements and signal integrity by mediating the current flow between the two wires.
3Adaptability or versatility
If a capacitor is charged only to a low voltage (e.g., 3.3V) associated with a microcontroller, then the system can operate with standard low-voltage components, but overall efficiency and usability are reduced for sensors requiring high peak current
Solution Approach 1:
The patent changes the voltage parameter of the energy storage capacitor from the conventional low voltage (3.3V) to a high voltage (e.g., 24V). This parameter change allows the capacitor to store significantly more energy (E = 1/2 CV²) while the shunt regulator manages the voltage to ensure the sensor receives appropriate current. The high-voltage capacitor, combined with the shunt regulator, enables the system to deliver high peak current while maintaining component compatibility through controlled voltage regulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high peak current sensors to operate efficiently in two-wire loops by managing power supply and maintaining loop performance, allowing continuous operation and clear data transmission without exceeding 4 mA output.
Implementation Method 1
The sensor device 300 may include a shunt regulator 302 configured to limit an input current received at the input terminal 170A to a maximum of 4 mA
Implementation Method 2
The sensor device 300 may include a capacitor bank 304 configured to store electrical energy
Implementation Method 3
The sensor device 300 may include a DC-DC converter 306 configured to convert a voltage output from the capacitor bank 304 to a lower voltage output
Implementation Method 4
Some sensors require high peak current to operate, for example to power sensor components thereof and/or to communicate signals relating to data obtained by the sensor component(s)
Data Source
AI summary
Apparatuses, systems, and methods are described for providing a sensor device. The system includes a control unit and a sensing unit. The sensing unit is coupleable to the control unit via a current loop and includes an input terminal coupleable to the current loop, at least one energy storage unit configured to be charged to a first voltage from the input terminal, a sensing element configured to sense an environmental parameter, wherein the sensing element receives power from the at least one energy storage unit at a second voltage, and wherein the second voltage is lower than the first voltage, a controller configured to receive a sensor signal from the sensing element and to generate an output signal, and an output terminal coupleable to the current loop and configured to transmit output corresponding to the output signal to the control unit via the current loop.