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User Guide
This square root extraction current to linear measurement converter will take your entered electrical signal with a square root characteristic over the range of 4 to 20 milliamps and calculate the corresponding linear measurement. After values have been entered a conversion scale will be shown which corresponds to your entered measurement range parameters.
Formula
This tool uses the following formula to calculate the the measurement reading output from a current signal input over a square root extraction 4-20mA range:
Measurement Rdg = Low Limit + (High Limit – Low Limit) x ((mA out -4) / 16)²
Parameters
Square Root Extraction Signal (4-20mA) Reading
Add the sqrt 4-20mA current loop signal reading that you wish to convert.
Measurement Unit
Enter the measurement unit associated with the output values.
Lowest Linear Measurement
Add the minimum possible value for the linear measurement range of the square root extractor device. For example zero would be a typical value for most instrumentation. A value in any engineering units can be used as long as it relates to a linear measurement, and the same unit is used for the Highest value.
Highest Linear Measurement
Add the maximum possible value for the linear measurement range of the sqrt extractor instrument, e.g. full scale or full range value. Any measuring units can be used as long as it relates to a linear measurement, and the same unit is used as for the Lowest value.
Linear Measurement Reading – Answer
This is the ideal converted linear measurement for your square root extraction instrument, which represents the expected reading from a perfect instrument without any errors. The answer value is displayed in the same engineering unit that you entered for the Lowest and Highest range points.
Help
Conversion precision
How precise is the conversion into measurement units?
The linear measurement Answer is calculated to a precision of 9 significant figures.
Convert sqrt 4-20mA to linear 4-20mA
Can I use this calculator to convert sq rt extraction 4-20mA to a normal 4-20mA signal?
Yes, just specify 4 for the Lowest limit and 20 for the Highest limit.
Linear to sqrt characteristic
How does the linear measurement change with respect to the sqrt current loop signal?
As the sqrt signal increases, the linear reading will be slower to increase in comparison to the sqrt signal and will gradually increase and eventually overtake the linear scale when comparing each with the percentage of full scale.
Switching input & output
Does it matter if the square root extraction signal is the input or the output?
No, it does not matter if the sqrt 4-20mA reading is an input or an output, the conversion will be the same to a linear measurement.
Quickly identifying sqrt or linear 4-20mA
Is there a quick way of determining whether a 4-20mA has a square root characteristic or a linear one?
A 12mA sq rt current loop signal which is 50% of the 4-20mA scale will correspond to 25% of a linear measurement range.