User`s manual

7-20
Countermeasure:Connection of bleeder resistance
As a countermeasure, a bleeder resistance can be inserted in the input side of the
input module as shown below.
Choose the bleeder resistance value R to meet the following conditions:
Composite impedance of the bleeder resistance and the input impedance
i
L
: Current leakage of the input device
V
in OFF
: Input of the input module OFF level voltage
R
in
: Input impedance of the input module
V: Input power supply voltage
In this case, the rating electric power W is,
[Example] In case that the JW-212NA is used as an input module at the input power supply voltage of
24 V, and that the leakage current of the input device is 5 mA,
i
L
= 5 mA
V
in OFF
= 5 V
R
in
= 3.3 k ohm
V = 24 V
If R is 0.78 k ohm,
W will be 2.3 W.
iL ＝ ＜V in OFF
R in ×R
R in ＋R
R＜ ×0.5
Vin OFF×Rin
Rin× iL− Vin OFF
Margin
R＜×0.5＝0.78k ohm
５×3.3
3.3×５-５
W＞ ×３＝2.22 W
24
2
0.78×10
3
Rin
Bleeder
resistance
R
Input module
i
L
Input
power
supply
Input device with
leakage current
IN
COM
W＞ ×３
V
2
R
Margin