424
Analog I/O Units Section 7-4
(5) Refer to the following diagram regarding wiring disconnections when volt-
age input is being used.
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 out-
put voltage of the other connected device will be generated. If that volt-
age 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 dia-
gram, the negative (-) side will be used in for both devices and open-cir-
cuit detection will not be possible.
This problem will not occur for current inputs even if the same power
supply is used.
(6) When external power is supplied (when setting the range code), or when
there is a power interruption, pulse-form analog output of up to 1 ms may
be generated. If this causes problems with operation, take countermea-
sures such as those suggested below.
• Turn ON the power supply for the CP1H 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 CP1H CPU Unit.
24 VDC
A
CB
Analog
output
device 1
Analog
output
device 2
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