Omron DEVICENET#05-2003 Operation Manual page 114

Analog Input Units
Common Power Supply
for Input Devices
Power
supply
Converted Data
Conversion Time
104
If an open-circuit occurs when more than one input device is using the same
power supply, and voltage input is being supplied, the following situation will
occur (this does not apply when current input is being supplied).
Input
device
Input
device
If an open-circuit occurs at A in the above diagram, a sneak circuit will be cre-
ated in the direction of the arrow, and even though the circuit is open, a volt-
age will exist. This voltage will be approximately 1/3 to 1/2 of the output of the
input devices in the part of the circuit that is not open. (The same will apply if
an open circuit occurred at B.) With such a voltage present in the circuit, the
open-circuit will not be detected. When voltage input is being supplied, either
set up the input devices so that they are not using the same power supply, or
use isolators for each input.
First word
First word + 1
First word + 2
First word + 3
If the conversion data is a negative number, it is expressed as a two's comple-
ment. To obtain an absolute value from this two's complement, the NEG
instruction is useful.
The conversion data is refreshed every 4 ms for all 4 points.
Analog Input Unit
Internal
circuits
Voltage
occurrence
Input 0 converted data
Input 1 converted data
Input 2 converted data
Input 3 converted data
Section 5-1
Bit