Advantages and Disadvantages of using a 4 to 20 mA Signal

A 4-20mA current signal has become very popular for many applications beyond it's original intended purpose in the process industry.  It is now used throughout industry as the preferred measurement and control signal for many different types of systems.

Despite the popularity of the 4-20mA signal, it is not the best solution for every application and here are some of the 'for' and 'against' reasons for determining whether it is the right type of signal for your application.

Advantages

• It can be run over long distances with minimal signal losses compared to voltage type signals
• A varying current loop load impedence or supply voltage will not significantly affect the signal as long as it does not exceed recommended component limits
• Rugged signal with low electromagnetic susceptibility
• Saves on cable wire becasue it only needs 2 wires to function
• Live zero reading verifies sensor is electrically functional

Disadvantages

• High power consumption compared to other analogue signal types
• Elevated output at zero reading
• Supply not isolated from output
• Increasing circuit load resistance causes will reduce available supply voltage output device

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