Instrumentation Calculators

4-20mA to PV scaling calculator

A physical process value, such as a temperature, pressure, liquid level, or other physical quantity, is transferred via 4-20 mA signals. The corresponding physical process value is represented by the mA current in the loop.


A 200 degree temperature is measured via a 4-20 mA temperature transmitter with a 0 to 1000 degree Celsius temperature range. The signal loop will then generate a current of 7.2 mA.

The 4-20mA scaling calculator below converts the current to the measured process value:

The following calculations provide the basis for the 4-20mA to PV scaling calculator:

 Formula for converting a current (I) value to a physical process value (PV):

4- 20mA scaling calculator into PV formula

Pv=[(Pv high-Pv low)/(I high-I low)]*(I-I low)+Pv low

In this article, scaling is utilised to establish the connection between a field value (in this case, mA) and a process value (e.g. Temperature, Pressure, Level, flow and etc.).

A linear characteristic is used to convert the electrical mA current loop signal to a physical value. When describing the relationship between the present mA signal and physical process value, this feature is used.

The conversion from a physical value with a starting value other than zero requires extra care. A pressure signal, for instance, ranging from -1 to 1 bar. The current is 12 mA at 0 bar of process pressure. It is suggested that you utilise a scaling calculator in this case because the characteristic between the physical process value and current is irrational due to the 4 mA starting current.

Other typical examples of measuring transmitters with this issue include pH sensors and temperature signals ranging from -80 to 20 degrees Celsius.

When dealing with actual-life environments, it could be required to test instruments using a 4-20 mA simulator. Scaling can be verified and checked quite easily because the simulator permits manual control of the current in the loop.

Click here for moreĀ Instrumentation Calculators

Sundareswaran Iyalunaidu

With over 24 years of dedicated experience, I am a seasoned professional specializing in the commissioning, maintenance, and installation of Electrical, Instrumentation and Control systems. My expertise extends across a spectrum of industries, including Power stations, Oil and Gas, Aluminium, Utilities, Steel and Continuous process industries. Tweet me @sundareshinfohe

Related Articles

Back to top button