PLC Scaling

Converting the input ( analog voltage - 0 to 10V /current - 4–20 mA) into the understandable engineering values as per industry standard ( analog voltage - 0 to 10V /current - 4–20 mA) is called “ SCALING ” .

The Input instrument which is producing analog values( for eg. 0–10V) is give to Analog Input Module. This module converts that analog values into counts/raw value (i.e) 0 to 32768.

Whenever the input instrument produces 0V our PLC reads 0.

Similarly , Input Instrument 5V = PLC reads 16384.

Input Instrument 10V = PLC reads 32768.

So using this raw value , we can scale our PLC to convert the Input to Output as engineering values as per industry standard so that we can control the output device.


Analog signal is having standard 16 bit resolution for Input and Output for the PLC.

So every analog signal has standard range for measuring single for current and voltage.

Voltage Range : ± 10V

Current Range : 4 to 20ma

When PLC is taking analog signal from Sensors weather current or voltage form its converting in Digital Binary form between range 20 to 215. Total 16 bit and if we convert in decimal form then it would be as below range –

0 to 32768.

This value called as Raw Value for the PLC, but we need engineering value to understand the calibration and measurements.

Engineering Values means 0 to 100 ‘C. Temperature

0 to 10 bar Pressure

100 l/sec Flow Etc.

So we have to convert Raw value in engineering value and this procedure is called as SCALING in PLC for analog signal. And its ultimately linear graph for Engineering value Vs Raw Value.

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