The 4-20 mA current loop is commonly used to convey what type of signal in process control systems?

The 4-20 mA current loop is commonly used to convey what type of signal in process control systems?

• A. Analog electrical signal
• B. Digital electrical signal
• C. Pulsed signal
• D. Radio frequency signal

Answer: (A)

A 4-20 mA loop carries an analog signal. In process control, a transmitter converts a physical quantity like temperature or pressure into a current that varies continuously from 4 mA up to 20 mA. The exact current level within that range represents the measured value, with 4 mA as the minimum and 20 mA as the maximum. Using current rather than voltage makes the signal robust over long distances and through varying cable resistance, so the measurement stays accurate even with changing loads. This continuous current variation is what defines an analog signal. The other options describe digital, pulsed, or wireless signals, which do not match how a 4-20 mA loop conveys information.

A 4-20 mA loop carries an analog signal. In process control, a transmitter converts a physical quantity like temperature or pressure into a current that varies continuously from 4 mA up to 20 mA. The exact current level within that range represents the measured value, with 4 mA as the minimum and 20 mA as the maximum. Using current rather than voltage makes the signal robust over long distances and through varying cable resistance, so the measurement stays accurate even with changing loads. This continuous current variation is what defines an analog signal. The other options describe digital, pulsed, or wireless signals, which do not match how a 4-20 mA loop conveys information.