5. Analog Signal Processing
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Analog Introduction
An analog value is continuous,
not discrete
Typical analog inputs and outputs for PLCs
Inputs signal
Output signal
• Oven temperature • Fluid valve position
• Fluid pressure
• Motor position
• Fluid flow rate
• Motor velocity
 Module Analog Input: digital-toanalog (D/A) conversion
 Module Analog Output: analogto-digital (A/D) conversion
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Analog Input Module
The continuous voltage value must
be sampled and then converted to a
numerical value by an A/D converter
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Analog Input
Analog input physical wiring in field
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Module Analog S7-1200
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Analog Value Representation
Analog Value Representation
Resolutions of the
Analog Values
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Module 2AI - CPU 1214C
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AI Digitized Measured Value
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AI Digitized Measured Value
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S7-1200 AI Configuration
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Analog Output
To set an analog output an integer is converted to a voltage
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Analog Output
To set an analog output an integer is converted to a voltage
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Analog Output
Analog output physical wiring in field
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Module 2AO - CPU 1214C
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AO Digitized Value
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AO Digitized Value
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S7-1200 AO Configuration
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Scale_X Function
Scales the normalized real parameter VALUE
where ( 0.0 <= VALUE <= 1.0 ) in the data type
and value range specified by the MIN and MAX
parameters:
OUT = VALUE (MAX - MIN) + MIN
SCALE_X parameter VALUE should be restricted to (0.0 <= VALUE <= 1.0)
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Norm_X Function
Normalizes the parameter VALUE inside the
value range specified by the MIN and MAX
parameters:
OUT = (VALUE - MIN) / (MAX - MIN),
where ( 0.0 <= OUT <= 1.0 )
NORM_X parameter VALUE should be restricted to (MIN <= VALUE <= MAX)
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AI Application
An analog input from an analog signal module or signal board using input in current is in the range 0 to
27648 for valid values. Suppose an analog input represents a temperature where the 0 value of the
analog input represents -30.0 degrees C and 27648 represents 70.0 degrees C
The resulting value is the temperature represented by the analog input in degrees C:
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AO Application
An analog output to be set in an analog signal module or signal board using output in current must
be in the range 0 to 27648 for valid values. Suppose an analog output represents a temperature
setting where the 0 value of the analog input represents -30.0 degrees C and 27648 represents
70.0 degrees C.
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