Instrumentation Calculators

Engineering Units to PLC Raw Counts Conversion Calculator 

An Engineering Units to Raw Counts Calculator is a useful tool that allows the conversion of the physical measurements made using the engineering units such as temperature, pressure, or flow rate into figures that are in raw count form that PLC or any other digital control system can process. Such raw counts are expressed in the form of sensor data without having gone through any further arithmetic calculation; the outcome usually falls within a certain range set by the resolution of the PLC.

Click here for Calculator/Instrumentationtool for Raw Counts value to Engineering Units

This calculator is essential in industrial automation and process control systems, where:

  1. DCS, PLCs, or microcontrollers frequently call for raw count early values to perform calculation or interact with another system.
  2. Sensors give sensible units of measurement (°C, PSI etc.). All these have to be converted back to raw count form for correct system interfacing.”
  3. This calculator is employed by engineers for purposes of approximating raw counts useful in testing and calibrating equipment.
  4. Closes values properly for the specified ranges of sensors and controllers.
  5. Enables the linking of devices that have apparently dissimilar data types or scales.

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  1. Min Scaled Value: Minimum value of the engineering unit range.
  2. Max Scaled Value: Maximum value of the engineering unit range.
  3. Min Raw Value: Minimum raw count (e.g., 0 for most systems or specific values for certain sensors).
  4. Max Raw Value: Maximum raw count (e.g., 65,535 for 16-bit, 4,294,967,295 for 32-bit PLCs).
  5. Scaled Value: The engineering unit value to be converted into raw counts.
  1. Input the known minimum and maximum values of both the raw count range and the engineering unit range.
  2. Enter the engineering unit value you wish to convert to raw counts.
  3. Apply the formula:
  1. The calculator will output the raw count value corresponding to the input engineering unit value.

A temperature sensor gives scaled values from -50°C to +150°C while the raw counts are in the range of 0 to 65,535 in a 16-bit PLC data type as represented in the unsigned integer format. The system gets a signal and it shows 75°C of temperature and raw count values are required to set the programming of the PLC.

  1. Scaled Value (Temperature) = 75C
  2. Min Scaled Value = −50C
  3. Max Scaled Value = 150C
  4. Min Raw Value = 0 (PLC raw count minimum)
  5. Max Raw Value = 65,535 (PLC raw count maximum)

The formula to calculate the raw value from scaled engineering units is:

Since raw counts must be integers, round 40,959.375 to the nearest whole number:

Raw Value=40,959

For a scaled temperature value of 75°C, the corresponding 16-bit raw count value is 40,959.

The sensor’s reading of 75C falls within the scaled range of −50C to 150C, and the calculated raw count of 40,959 represents this value as interpreted by the 16-bit PLC. This make sure that there is the right transfer of information between the sensor and the PLC system.

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The unprocessed value of a variable as it is kept in memory is known as the raw value, or native value. This value is frequently encoded or in a format that is directly connected to the output of the sensor or device.

In memory, a frequency variable of 50.2 Hz could be represented by an integer, like 502, because of scaling.

In a PLC, “counts,” which are integers that represent the electrical output of the sensor within its natural range, are frequently used to convey the raw input

The practical measurement that a sensor is detecting is represented by engineering units (EUs), which are physical values like temperature, pressure, or flow rate. For instance:

The PLC may interpret a temperature sensor’s raw value, which ranges from 0 to 18,000 counts. This range could be equivalent to 0°C to 150°C in engineering terms.

The engineering units in this case offer significant practical values that are based on the raw counts.

Standardized measuring units called engineering units are used to quantify physical characteristics like temperature (e.g., degrees Celsius or Fahrenheit).

Pressure (such as psi or Pascals)

Rate of flow (liters per second, for example)

Energy, such as Joules

These units enable uniformity and understanding in a variety of engineering and industrial settings.

The unscaled digital value produced by a sensor or analog input module in a PLC is known as a raw count. This amount:

  • is usually an integer that represents the sensor’s electrical signal.
  • falls under a predetermined range, for example, 0 to 65,535 for a 16-bit input card or 0 to 8,092 for a 12-bit analog input card.
  • For practical purposes, the raw count needs to be adjusted to engineering units.

Scaling in a PLC converts raw input values (counts) into meaningful engineering units (e.g., °C, psi). 

The formula for scaling is:

Where:

  • Raw Input Value = Raw count from the sensor
  • ZeroIn = Minimum raw value of the input range
  • SpanIn = Maximum raw value of the input range
  • ZeroOut = Minimum value of the desired engineering unit range
  • SpanOut = Maximum value of the desired engineering unit range
  • Raw Values: Crucial for calibration, troubleshooting, and communication at the hardware level.
  • Units of Engineering: Enable relevant data interpretation and analysis by engineers and operators to improve process control and decision-making.

The smooth integration of sensors, PLCs, and industrial processes is made possible by this differentiation and conversion between raw values and engineering units.

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

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