Filter
Top Products
6F3B0250
64
T1/T1S User’s Manual
3. I/O Application Precautions
(5) Countermeasures against leakage current
When a switch with an LED or an AC output sensor is used, the input sometimes cannot
recognize that the switch is off due to the current leakage. In this case, install a bleeder
resistor to reduce input impedance.
DC input type AC input type
Select a bleeder resistor according to the following criteria:
(a) The voltage between the input terminals must be lower than the OFF voltage
when the sensor is switched off.
(b) The current must be within the allowable range when the sensor is switched on.
(c) Calculate the wattage of the bleeder resistor by multiplying the current when the
sensor is switched on times three.
Note) The above solution cannot be applied to the T1-16 dry contact input.
(6) Countermeasures against induced current
With ac input signals, if the external cable is long or if a multi-core cable is used, an
induced current can flow from the charged wire to the open wire, in proportion to the
capacities of the cables. In this case, sometimes the voltage reaches the level of the ON
input even though the contact is open, causing the input to malfunction for no apparent
reason.
The usual practice when this happens is to reduce input impedance. Install a resistor or a
resistor and capacitor between the input and common terminals, or use shielded cables.
Such precautions are necessary when dealing with a large number of ac input signals.
T1
input
circuit
Bleeder resistor
LED
R
C
V
C
T1
input
circuit
Bleeder resistor
R
V
AC
output
sensor
T1
input
circuit
C
Open contact
V
~
CTi Automation - Phone: 800.894.0412 - Fax: 208.368.0415 - Web: www.ctiautomation.net - Email: info@ctiautomation.net