When to apply Square Root Extraction for Differential Pressure Transmitter ?

When to apply Square Root Extraction for Differential Pressure Transmitter?

In recent times, I've gotten many questions about square root extractors and where should we use square root extractors? So I have decided to make one blog to cover this topic. In this blog, I will explain what square root extract is and where we should do square root extraction at the DPT side or DCS side.

First of all, let's start with what is the square root extract. As we know that the relationship between flow rate and differential pressure is nonlinear.

in other words, differential pressure developed by a Venturi, orifice plate, Pitot tube, or any other accelerations base flow element is proportional to the square of the flow rate.

A square root extractor is an electronic or pneumatic device that converts the square root signal of a flow transmitter with the corresponding linear slow signal.

In past days and in pneumatic instrumentation. This square root function was performed in a separate device called square root extract.

the Foxboro model 557 and Moore product model 65 are the devices which is used for square root extractor, in the past .

As you can see, this is the more square root extract which is used as a square root extractor.

Nowadays, all the smart DNA transmitter comes with square root extract functional, and to convert square root signal into linear force a user has to select this function for transmitting.

In this section, you will learn where should we do the square root extraction. This is a very common question that comes in everyone's mind. Sometimes, it is very confusing for a field engineer and system engineer to decide which square extraction needs to be done at the transmitter side or the DCS side.?

In this type of situation, where proper communication is needed between the field engineer and System Engineer. Sometimes the field engineer assumes that it will be done in DCs and he purchases a transmitter without a square root extractor function.

In other side, the system engineer assumes it will be done and transmitted .and nobody does it which is not correct. Conversely, in some cases, the square root extraction is done in both places which again is not correct.

In an ideal way, square root extraction should be done in one place only. Either square root extraction should be done at transmitter side or it should be done at DCS side but not both sides. Ideally, it is advisable to get this task to the system side. The reason behind this approach is that the transmitters electronic computational capability is not superior as compared to system or DCS site.

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