Limitless Processes -The 4…20 mA Loop| Visaya Weekly Episode 40

The 4-20mA pill for humans?

Well, unfortunately, this kind of pill only exists in movies.

But, what if I told you that there is a pill that your plant could take to make it smarter!

Let’s go back in time a little…

In the 1950s the concept of the  4-20mA loop was introduced in plants to replace pneumatic systems for measurement and control.  This is an analog signal that works on the 0 – 100 % principle.

Let me illustrate this concept with an example:

You have a bioreactor for a pharmaceutical company that operates between ambient temperature to 160 degrees Celsius.

When you setup the temperature transmitter you will:

Set up your lower temperature  10

As 4-20mA and your highest around 160

The control system then understands that there is a value of temperature related to value current between 4 and 20 mA. Thus 4-20mA.

But that’s about it. This is still one of the most used signals even today, in the 1990s the first attempt for digitalization was used with HART.

Stick around to learn more about how to make your process smarter next week.

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