How to convert analog (4-20mA) to voltage

Field Network Q&A

I need a way to convert 4-20mA to volts. I found a document that says we can use a Rosemount 644 and switch to FF, but will it get me my volts?

Expert’s answer : How to convert analog (4-20mA) to voltage

Good question – and easy to solve – but with more than one way to solve it. I’ll bet your control system (or whatever you have to read the signal from the field) can read volts too. But in case it can’t, let’s give you some other options.

First off, you can buy a converter and install it in your panel. A converter will receive the analog signal from your field device and convert it to volts. Easy, right? On the downside, it costs more than other options. But hey, vendors created converters specifically for this problem, so it offers a lower fail rate than the next choice.

Next, you can use a simple high-precision resistor.  A resistor of 250 ohms will create a voltage drop that you can read. And you can install a resistor in the field or in the signal input of your control system or other control stuff.

Courtesy of Emerson

And as for the Rosemount 644, it’s a temperature device that can read analog signals and convert them in FOUNDATION Fieldbus (FF). This technical solution lets you avoid changing the field device to a proper FF device. So you’ll often find temp devices in an FF network working as converters for budget-conscious consumers.

On the plus side, if you have analog in the field, then you won’t need an extra transmitter. You can use these solutions as workarounds. Hope that helps!

Read these articles to learn more about analog, HART and FOUNDATION Fieldbus:

HART Communicator 

What does a HART communicator do?

FOUNDATION Fieldbus or HART?

Both Foundation Fieldbus and HART can provide field data to the marshalling cabinet. Whicch is more reliable for the oil and gas industry ?

Analog and digital communication

What is the difference between HART and FOUNDATION Fieldbus ?

Related tags: 4-20mA Basic Converter field communication Field Network Foundation Fieldbus HART Principle Q&A Solutions Voltage
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