Omron CP1E CPU UNIT SOFTWARE User Manual page 262

15 Analog I/O Function
5 Refer to the following diagram regarding wiring disconnections when voltage input is being used.
Analog
input
device 1
Analog
input
device 2
24 VDC
Example: If analog input device 2 is outputting 5 V and the same power supply is being used for both
devices as shown above, approximately 1/3, or 1.6 V, will be applied to the input for input device 1.
If a wiring disconnection occurs when voltage input is being used, the situation described below will
result. Either separate the power supplies for the connected devices, or use an isolator for each input.
If the same power supply is being used by the connected devices and a disconnection occurs at points
A or B in the above diagram, an unwanted circuit path will occur as shown along the dotted line in the
diagram. If that occurs, a voltage of approximately 1/3 to 1/2 of the output voltage of the other con-
nected device will be generated. If that voltage is generated while the setting is for 1 to 5 V, open-circuit
detection may not be possible. Also, if a disconnection occurs at point C in the diagram, the negative (-)
side will be used in for both devices and open-circuit detection will not be possible.
This problem will not occur for current inputs even if the same power supply is used.
Note When external power is supplied (when setting the range code), or when there is a power interruption, pulse-
form analog output may be generated. If this causes problems with operation, take countermeasures such
as those suggested below.
(1) Countermeasure 1
• Turn ON the power supply for the CP1E CPU Unit first, and then turn ON the power supply for the load
after confirming correct operation.
• Turn OFF the power supply for the load before turning OFF the power supply for the CP1E CPU Unit.
(2) Countermeasure 2
• Control the machine not only by analog output but also by other signals (additional start/stop control sig-
nal for machine).
15-4
A
B C
CP1E CPU Unit Software User's Manual(W480)