Omron DEVICENET#05-2003 Operation Manual page 113

Analog Input Units
Averaging Function
Setting
Open-circuit Detection
Function
4 to 20 mA
The 4- to 20-mA range corresponds to the hexadecimal values 0000 to 1770
(0 to 6000). The entire data range is FED4 to 189C (–300 to 6300). If the input
current falls below 3.2 mA, the open-circuit detection function will activate and
the converted data will be set to 7FFF.
Converted data
Hexadecimal (Decimal)
189C (6300)
1770 (6000)
7FFF
0000 (0)
FED4 ( 300)
The averaging function can be enabled for all inputs (0 through 3) by turning
ON pin 7 of the DIP switch. The averaging function outputs the average (a
moving average) of the last eight input values as the converted value. Use this
function to smooth inputs that vary like the one in the following diagram.
Note The time required for refreshing converted data remains one ms/point when
the averaging function is enabled. The first communications data after the
power is turned ON will be output after averaging eight samples.
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 7FFF.
The open-circuit detection function is enabled or cleared when data is con-
verted. If the input returns to the convertible range, the open-circuit detection
is cleared automatically and the output returns to the normal range.
3.2 mA
4 mA
Section 5-1
20 mA 20.8 mA
Actual input
Input after averaging
Time
Current
103