Why a 0 mA Signal is Not Practical?
Why a 0 mA Signal is Not Practical and Advantages of 4-20 mA Standard: Industry Preference
Engineering Complexity and Cost:
- Designing circuitry for 0 mA signals requires more sophisticated components.
- Circuitry must be able to handle a wider range of signal values, adding complexity.
- This complexity increases manufacturing costs for devices utilizing 0 mA signals.
- 4-20 mA signals offer a simpler and more standardized design approach.
System Fault Detection:
- 0 mA signals make it challenging to distinguish between zero readings and system failures.
- Live zero signals (e.g., 4 mA representing 0% measurement) enable faster fault detection.
- In case of a system fault, a live zero helps quickly identify issues such as line breaks or wiring faults.
- This capability enhances system reliability and reduces downtime for troubleshooting.
Powering Devices:
- 0 mA signals do not provide any current flow to power devices in the loop.
- Loop-powered devices, such as transmitters and displays, require a minimum current to operate.
- The 4-20 mA signal ensures a continuous flow of current, meeting the power requirements of connected devices.
- This allows for reliable operation of instrumentation and control devices without the need for additional power sources.
Advantages of 4-20 mA Standard:
- Easier Wiring: Standardized signal range simplifies wiring connections and configurations.
- Cost-Effectiveness: Manufacturing costs are lower due to simpler circuitry and standardized components.
- Long-Distance Transmission: 4-20 mA signals are less susceptible to voltage drops over long transmission distances.
- Reduced Electrical Noise: The signal range is less affected by background electrical noise, ensuring more accurate readings.
- Lower Risk of Electrical Shock: The low current levels of 4-20 mA signals pose minimal electrical shock hazards.
- Safety in Hazardous Environments: The signal range is suitable for designing intrinsically safe equipment for hazardous areas.
Industry Preference:
- The process control industry has widely adopted the 4-20 mA signal range as the standard for transmitting process data.
- It offers a balance of efficiency, reliability, and safety, making it well-suited for various industrial applications.
- The 4-20 mA standard has become ingrained in industry practices and is supported by regulatory standards and guidelines.