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MELSEC-Q 
2   INPUT MODULE SPECIFICATIONS 
2.22 QX81-S2 DC Input Module (Negative Common Type) 
Type 
Specifications 
DC input module (Negative common type) 
QX81-S2 Appearance 
Number of input points  32 points 
 
Isolation method  Photocoupler 
Rated input voltage  24VDC (+20/-15%, ripple ratio within 5%) 
Rated input current  Approx. 6mA 
Input derating  Refer to the derating chart. 
ON voltage/ON current  15V or higher/3mA or higher 
OFF voltage/OFF current  5V or lower/1.7mA or lower 
Input impedance  Approx. 3.6kΩ 
Response 
time 
OFF to ON 
1ms/5ms/10ms/20ms/70ms or less (configured in PLC parameter)  1  
(Default: 10ms) 
ON to OFF 
1ms/5ms/10ms/20ms/70ms or less (configured in PLC parameter)  1  
(Default: 10ms) 
Dielectric withstand voltage  560VAC rms/3 cycles (altitude 2000m) 
Insulation resistance  10MΩ or more by insulation resistance tester 
Noise immunity 
By noise simulator of 500Vp-p noise voltage, 1 s noise width  
and 25 to 60Hz noise frequency 
First transient noise IEC61000-4-4: 1kV 
Protection degree  IP2X 
Common terminal arrangement  32 points/common (common terminal: 17, 18, 36) 
Number of occupied I/O points  32 points (I/O assignment is set as a 32-point input module.) 
Operation indicator  ON indication (LED) 
External connections  37-pin D-sub connector 
Applicable wire size 
0.088 to 0.3mm
2 
(For A6CON1E) 2 
Applicable connector  A6CON1E, A6CON2E, A6CON3E (optional)  
Applicable connector/terminal block 
converter module 
A6TBX36-E, A6TBX54-E, A6TBX70-E 
Internal current consumption 
(5VDC) 
75mA (TYP. all points ON) 
(0.08A is shown on the rating plate of the module.) 
Weight 0.16kg 
 
Derating chart  Pin-Outs 
Pin 
No. 
Signal 
No. 
Pin 
No. 
Signal 
No. 
 
 
Module front view 
1 X00 9 X10 
20 X01 28 X11 
2 X02 10 X12 
21 X03 29 X13 
3 X04 11 X14 
22 X05 30 X15 
4 X06 12 X16 
23 X07 31 X17 
5 X08 13 X18 
External connection 
24 X09 32 X19 
 
6 X0A 14 X1A 
25 X0B 33 X1B 
7 X0C 15 X1C 
26 X0D 34 X1D 
8 X0E 16 X1E 
27 X0F 35 X1F 
17 COM 37 Vacant 
36 COM 19 Vacant 
18 COM     
 
1: For the setting method, refer to Section 1.3.1. 
2: When using A6CON2E or A6CON3E, refer to Chapter 7. 
 
100
90
80
70
60
50
40
0102030405055
30
20
10
ON
ratio
mbient temperature
(   )
(%)
(31.25%) 24VDC
(18.75%) 28.8VDC
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1