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Analog Input Units Section 7-2
Averaging Function For analog inputs, the averaging function operates when the averaging bit is
set to 1. The averaging function outputs the average (a moving average) of
the last eight input values as the converted value. If there is only a slight vari-
ation in inputs, it is handled by the averaging function as a smooth input.
The averaging function stores the average (a moving average) of the last eight
input values as the converted value. Use this function to smooth inputs that
vary at a short interval.
Open-circuit Detection
Function
The open-circuit detection function is activated when the input range is set to
1 to 5 V and the voltage drops below 0.8 V, or when the input range is set to 4
to 20 mA and the current drops below 3.2 mA. When the open-circuit detec-
tion function is activated, the converted data will be set to 8,000.
The time for enabling or clearing the open-circuit detection function is the
same as the time for converting the data. If the input returns to the convertible
range, the open-circuit detection is cleared automatically and the output
returns to the normal range.
Procedure
Writing Set Data and
Reading A/D Converted
Values
4 mA 20 mA
20.8 mA
3.2 mA
FDA8 (−600)
3138 (12600)
2EE0 (12000)
0000 (0)
0 mA
Converted Data
Hexadecimal (Decimal)
Connect and wire Units.
Create a ladder program.
• Connect Analog Input Units.
• Wire to analog output devices.
• Write set data to output words (n+1, n+2).
• Set use of inputs.
• Select input signals using range codes.
• Set use of averaging.
• Read A/D converted values from input words
(m+1 to m+4).
• For current inputs, confirm that there is no open
circuit.
CPU Unit
MOV(021)
Set data (inputs 1, 2)
Set data (inputs 3, 4)
Analog input 3 converted value
Analog input 4 converted value
Analog Input Unit
Ladder program
Analog input 1 converted value
Analog input 2 converted value
Analog devices
Temperature sensor
Pressure sensor
Speed sensor
Flow sensor
Voltage/current meter
Other devices
Writes the set data.
Reads the converted
value.
“m” is the last input word and “n” is
the last output word allocated to the
CPU Unit or previous Expansion
Unit or Expansion I/O Unit.
Word (n+1)
Word (n+2)
Word (m+1)
Word (m+2)
Word (m+3)
Word (m+4)
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