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

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Why choose 4 mA instead of 10 mA?

Why choose 4 mA instead of 10 mA?

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

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Why choose 4 mA instead of 10 mA?

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- [Instructor] Another question is why choosing 4 mA, instead for example 10 mA? One of the suggestions is that it is similar to all other industrial scales that having the low-end value, live zero, at 20% of the high-end value. So for example, 20% times 15 equals 3 pounds per a square inch gauge. 20% times 20 equals 4 mA, 20% times 50 equals 10 mA, and 20% times 5 equals 1 voltage DC. So for the 4-20 mA current loop, the low-end value is 4 mA and the high-end value is 20 mA, meaning the 4 mA is actually 20% of 20, the high-end value. Also, making the high-end value five times the low-end value. Another suggestion is to accommodate for this that some PLC input cards or modules don't really measure the 4-20 mA current loop directly, but instead measure voltage. For example, this Omron MAD44 analog input module that I used in our previous wiring example, showing that it accepts both current and voltage input…

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