From the course: Input Sensors with PLC: 4-20 mA Current Loop

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Industrial 4-20 mA current loop basics

Industrial 4-20 mA current loop basics

From the course: Input Sensors with PLC: 4-20 mA Current Loop

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Industrial 4-20 mA current loop basics

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- [Instructor] To understand the basics of the industrial 4-20 mA current loop circuit, I'm going to take you back briefly to one of the fundamental electrical concepts covering Ohm's Law. In this circuit, we have a voltage source and three resistors in series representing loads. Now, according to Ohm's Law, the voltage equals current times resistor value. If I want to measure the voltage across the first resistor, the voltage equals current times the value of the first resistor. The same thing if I want to measure the voltage across the second resistor, and the same for the third resistor. So as you can see, the voltage value is different across each resistor, meaning there is a voltage drop across each load, and the total voltage is the sum of each voltage drop, voltage one plus voltage two plus voltage three. However, the current is the same anywhere in the loop. So if I want to measure the current between resistor one…

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