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## Related Tools

## User Guide

This measurement to 4 to 20mA sqrt extraction converter tool will convert any linear measurement reading to the ideal current loop signal over a non-linear square root extraction scale of 4 to 20 milliamps. This is useful for measurement devices where one measurand is proportional to the square root of another measurand, e.g. flow through a pipe is proportional to the square root of the differential pressure. A square root extraction 4-20mA conversion scale is also displayed for each selected measurement range.

### Formula

This tool uses the following formula to calculate the current output signal over a square root extraction 4-20mA range from a specified linear measurement input reading and range:

SqRt mA out = 4 + (16 x √ ((Rdg – Low Limit) / (High Limit – Low Limit)))

### Parameters

#### Measurement Unit

Enter the measurement unit associated with the input values.

#### Linear Measurement Reading

Add the measurement value you wish to convert from, in any engineering units. Please use a value which relates to the same engineering units as used for the “Lowest” and “Highest” values.

#### Lowest Linear Measurement

Enter the lowest range value for the measurement instrument you are converting, for most application s this will be zero. Please use a value which relates to the same engineering units as used for the “Reading” and “Highest” values.

#### Highest Linear Measurement

Input the highest range value for the measurement equipment you are converting, which is typically described as the full range or full scale. Please use a value which relates to the same engineering units as used for the “Reading” and “Lowest” values.

#### Square Root Extraction Signal (4-20mA) – Answer

This is the 4-20mA square root extraction signal that you would expect excluding any errors contributed by the measurement instrument. The result given is displayed in milliamps (mA) relative to a non-linear 4 to 20 mA sqrt extraction signal scaling.

## Help

### Conversion precision

*How precise is the conversion to sq rt 4-20mA?*

The square root extraction 4 to 20 mA signal “Answer” is displayed to a precision of 9 significant figures.

### Rangeable instrument

*What do I use for the highest range value if I am using a rangeable instrument?*

Use the highest value of re-scaled range rather than the nominal base range.

### Input or Output

*Does the sqrt 4-20mA signal represent an input or an output signal?*

It can be either, for example you could use it to convert the pressure input to a dp pressure transmitter to determine the perfect square root output expected or you could use it to determine the expected measurement if your device is accepting a sqrt current loop input and converting it back to a linear scaled value.

### 4-20mA to 4-20mA

*Can I use this square root converter to convert a linear 4-20mA signal to a sqrt 4-20mA signal?*

Yes, just specify 4 for the “Lowest” value and 20 for the “Highest” value and the linear milliamp measurement you wish to convert as the “Reading”.

### Percent scaling

*Is it possible to use percent of full scale (%FS) rather than measurement units to input a reading?*

Yes, any scale can be used as long as it is linear one. So for percentages you would enter zero for the “Lowest” value and 100 for the “Highest” value.

### 0 to 600 mmH_{2}O to output conversion

What is the square root output over a 4 to 20 mA signal scale for a linear pressure range of 0 to 600 mmH_{2}O?

### Formula for linear %FS to SqRt 4-20mA

*How to convert a percentage to ma in a square root flow transmitter, please show me a simple formula?*

Please use the following formula to convert a linear reading expressed as a percentage of full scale:

*[SqRt Output (mA)] = 4 + √([Linear Reading (%FS)] x 256/100)*