Omron CP1H CPU UNITS - PROGRAMMING 05-2007, Operation Manual

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393
Analog Input Units
Section 7-2
■
0 to 20 mA Inputs
■
4 to 20 mA Inputs
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.
Current in the 0 to 20 mA
range corresponds to hexa-
decimal values 0000 to 1770
(0 to 6,000). The range of
data that can be converted is
FED4 to 189C hex (-300 to
6,300). A negative current is
expressed as two’s comple-
ment.
Current in the 4 to 20 mA
range corresponds to hexa-
decimal values 0000 to 1770
(0 to 6,000). The range of
data that can be converted is
FED4 to 189C hex (-300 to
6,300). Current in the range of
3.2 to 4 mA is expressed as
two’s complement.
If an input is below the range
(i.e., less than 3.2 mA), the
open-circuit detection func-
tion is activated and the data
becomes 8,000.
0 mA 20 mA 21 mA
−
1 mA
Converted data
Hexadecimal (Decimal)
189C (6300)
1770 (6000)
0000 (0)
FED4 (
−
300)
Converted data
Hexadecimal (Decimal)
189C (6300)
1770 (6000)
0000 (0)
FED4 (
−
300)
4 mA 20 mA 20.8 mA
3.2 mA
0 mA