4-20mA: Understanding the Voltage Behind the Current
The 4-20mA current loop is a widely used communication protocol in industrial automation, process control, and instrumentation applications. It's a versatile and reliable method for transmitting analog signals over long distances, but have you ever wondered what voltage is behind this current?
What is 4-20mA?
The 4-20mA current loop is a two-wire connection that carries a current signal proportional to the measured parameter, such as pressure, temperature, or flow rate. The current ranges from 4mA to 20mA, with 4mA typically representing 0% of the measurement range and 20mA representing 100%. This allows for the transmission of analog signals over long distances without significant attenuation or distortion.
Voltage Requirements
To understand the voltage behind the 4-20mA current, let's explore the voltage requirements for the current loop. The voltage required to drive the 4-20mA current loop depends on the specific application and the devices involved.
Power Supply Voltage
A typical power supply voltage for a 4-20mA current loop is 12V or 24V DC. This voltage is used to power the transmitter, which converts the measured parameter into a current signal. The power supply voltage is usually provided by a separate power source or a power supply unit (PSU) specifically designed for industrial applications.
Voltage Drop
When transmitting the current signal over a long distance, there will be a voltage drop along the cable due to the resistance of the cable. The voltage drop must be taken into account when designing the system to ensure that the receiving device receives the correct current signal.
Voltage Limitations
The 4-20mA current loop is designed to operate within a specific voltage range. Exceeding this range can cause damage to the devices or affect the accuracy of the measurement. Typically, the voltage limitation is:
- Minimum voltage: 12V DC
- Maximum voltage: 30V DC
Conclusion
In conclusion, the 4-20mA current loop is a reliable and versatile communication protocol widely used in industrial automation applications. Understanding the voltage requirements behind the current is essential to design and implement a reliable system. By considering the power supply voltage, voltage drop, and voltage limitations, you can ensure accurate and reliable transmission of analog signals over long distances.
