Why you use 4-20mA for instruments?

The 4-20 mA current loop is widely used for instrumentation because it provides a reliable method for transmitting signals over long distances, minimizing the impact of electrical noise. The range starts at 4 mA rather than 0 mA to prevent signal loss and ensure that the system can detect instrument failures (a reading of 0 mA indicates a fault). Additionally, current signals are less susceptible to voltage drops, allowing for consistent and accurate readings in various environments. This standard also simplifies integration with control systems and ensures compatibility across different devices.