SIEMENS S7-300 SM 338 POS input module

OverviewSM 338 POS input module

  • Interface between max. 3 absolute-value sensors (SSI) and the CPU
  • For provision of the displacement encoder values for further processing in STEP 7 programs
  • Enables direct response of controller to encoder values in moving systems

Note:

Displacement measuring systems and precut/preassembled cables for counting and positioning functions are available under SIMODRIVE Sensor or Motion Connect 500.

Application

The SM 338 POS input module can be used as an interface between up to 3 absolute encoders and the S7-300 CPU. It makes position-encoder values available for subsequent processing in the control and provides the conditions for the control to respond directly to encoder values in systems under motion.


Design

The POS input module is equipped with:

  • 3 SSI encoder inputs
  • 2 digital inputs
  • 24 V DC encoder supply

Function

The POS input module converts SSI position-encoder signals from the process into digital values for the S7-300.

You can select either:

  • Cyclic encoder-value sensing

or

  • Encoder-value sensing isochronous to the PROFIBUS DP cycle.

The recorded values can be processed directly in the STEP 7 program so that a direct reaction is possible to encoder values in moving systems.

In addition, the SSI encoder states can be frozen via two digital inputs of the module. This permits further time-critical applications in the sector of position detection.


Technical specifications

Article number

6ES7338-4BC01-0AB0

SIMATIC S7-300, SIGNAL. MODULE

Supply voltage

Load voltage L+

  • ● Rated value (DC)

24 V

  • ● permissible range, lower limit (DC)

20.4 V

  • ● permissible range, upper limit (DC)

28.8 V

Input current

from load voltage L+ (without load), max.

100 mA

from backplane bus 5 V DC, max.

160 mA

24 V encoder supply

  • ● 24 V

Yes; L+ (-0.8 V)

  • ● Output current, max.

900 mA

Power loss

Power loss, typ.

3 W

Digital inputs

Input voltage

  • ● for signal “0”

-3 to +5V

  • ● for signal “1”

11 to 30.2 V

Input current

  • ● for signal “0”, max. (permissible quiescent current)

2 mA

  • ● for signal “1”, typ.

9 mA

Input delay (for rated value of input voltage)

for standard inputs

  • — at “0” to “1”, min.

300 µs

Cable length

  • ● shielded, max.

600 m

Encoder

Number of connectable encoders, max.

3

Connectable encoders

  • ● Absolute encoder (SSI)

Yes

  • ● 2-wire sensor

Yes

Encoder signals, absolute encoder (SSI)

  • ● Cable length, shielded, max.

320 m; 320 m at 125 kHz; 160 m at 250 kHz; 60 m at 500 kHz; 20 m at 1 MHz

Interrupts/diagnostics/status information

Alarms

  • ● Diagnostic alarm

Yes

Potential separation

Potential separation exists

No

Connection method

required front connector

20-pin

Dimensions

Width

40 mm

Height

125 mm

Depth

120 mm

Weights

Weight, approx.

235 g