Siemens SIMATIC S7-200 System Manual page 447

Table A-33 Setting RTD DIP Switches for the EM 231 Analog Input RTD Module
Switch 6
(2 Channel Module Only)
SW6
1 2 3 4 5 6 7 8
Switch 7 (Both Modules)
SW7
1 2 3 4 5 6 7 8
Switch 8 (Both Modules)
SW8
1 2 3 4 5 6 7 8
RTD 4 Wire
(most accurate)
A+ Sense +
A-- Sense --
R
L1
a+ Source +
RTD
R
L2
a-- Source --
Note: R = Lead resistance from a+ terminal to the RTD
L1
R = Lead resistance from a-- terminal to the RTD
L2
Figure A-25 Wiring the RTD to the Sensor by 4, 3, and 2 Wire
Open Wire Detect/
Out of Range
Upscale
(+3276.7 degrees)
Configuration Configuration
↑1 -- On
Downscale
↓0 -- Off
(--3276.8 degrees)
Temperature Scale
Celsius (_C)
Configuration
↑1 -- On
On
↑1
Fahrenheit (_F)
↓0 -- Off
Wiring Scheme
3-wire
Configuration
↑1 -- On ↑1 -- On
↓0 -- Off
2-wire or 4-wire
RTD 3 Wire
A+ Sense +
A-- Sense --
a+ Source +
a-- Source --
If R R
L1=
Technical Specifications
Setting
0 Indicates positive on open wire or out of range
1 Indicates negative on open wire or out of
range
Setting
0 The RTD module can report temperatures in
Celsius or Fahrenheit. The Celsius to
Fahrenheit conversion is performed inside the
module. d l
1
Setting
0 You can wire the RTD module to the sensor in
three ways (shown in the figure). The most
accurate is 4 wire). The least accurate is 2
wire, which is only recommended if errors due i
1
to wiring can be ignored in your application.
A+ Sense +
A-- Sense --
R
a+ Source +
L1
R RTD
L2
a-- Source --
, error is minimal.
L2
Appendix A
Description
Description
p
Description
)
hi h i l d d if
RTD 2 Wire
Set switch to
4-wire mode.
R
L1
RTD
R
L2
R +R =Error
L1 L2
d
433