Siemens S7 PLC Analog Inputs & Outputs Devices Overview

 

  • In This chapter we discuss about Siemens S7 PLC'S ( Analog Inputs , Analog Outputs , Signal Modules Status Indicators ,  and Power Supplies ) devices overview.

Analog Inputs

Chapter -14

4 channel Analog input signal Module

  • An analog input signal is generated by a sensor that provides voltage or current that can vary within a range such as 0 to 10 volts or 4 to 20 milliamps.
  • An analog input signal module converts the current or voltage to a binary value that the CPU stores for use in the user program.
  • The number of bits in the binary value is referred to as the channel resolution.
  • The more bits the greater the number of values that can be represented.
  • The resolution available depends on the module.
  • For example, the accompanying graphic shows a signal module with a channel resolution of either 13 bits or 16 bits depending on the module version.
  • Temperature measurement is an example of an application that requires special signal processing.
  • Two types of sensors commonly used to measure temperature are Thermocouples and Resistance temperature detectors (RTDS).


  • A Thermocouples is a Temperature sensor made from two dissimilar metals joined at a point called a junction.
  • Thermocouple produces a small voltage that is Temperature dependent.
  • An RTD also called a Resistance Thermometer is a Temperature sensor made from a metal such as platinum, nickel, or copper that varies in resistance in a predictable manner as temperature varies.
  • There are various types of Thermocouples and RTD'S, and each type has different characteristics that determine its application range.
  • Because Thermocouple and RTD signals are different and require special processing some Siemens PLC'S have thermocouple and RTD signal modules.
  • However the S7- 1500 PLC analog input signal module shown in the accompany graphic can be used with a variety of analog signals  including RTD and thermocouple signals.


Analog Outputs

2 Channel Analog output module

  • When a CPU sends a numerical value to an analog output channel, the analog module converts the value to a voltage or current within the range set up for the output channel.
  • The channel is typically connected to an analog output device that is controlling something in a machine or process, such as motor speed, valve position, or temperature.
  • PLC analog output signal modules vary in the number of output channels, channel resolution, and output signal types.
  • The module shown in the accompanying graphic has two analog output channels.
  • These channels can be set up for either the -10 to +10 volts range or the 0 to 20 milliamps range.
  • The output resolution is 14 bits for the voltage range and 13 bits for the current range.


Signal Module Status Indicators

  • Signal modules have LED status indicators that are useful for system Installation and Troubleshooting.
  • For example the accompanying graphic shows two S7-1200 signal modules a combination digital input/output signal module and a combination analog input/output signal module.

  • Both modules have a status LED for each channel.
  • The digital channel status LED is green and turns on when the input or output is on.
  • The analog channel LED is green when the channel has been configured and is active and red when there is a channel error.
  • Both modules also have a diagnostic LED that is green when the module is operational and red when the module is defective or non-operational.

Power Supplies

  • Multiple system power supply types are typically available for a PLC model to match the system voltage.
  • System power supplies also specify a power budget which is the available power that a supply can provide to interconnected modules.
  • A load power supply provides power to input and output devices and channel circuits.
S7-1500 PLC Load power supply

  • In some cases, the load power supply also provides power to other PLC modules including a system power supply module.
  • Because input and output devices vary considerably in terms of their current voltage and power requirements load power supplies come in a variety of types and capabilities.
  • For example the accompanying graphic shows a load power supply module for an S7-1500 PLC that mounts on the mounting rail with other modules.
  • Siemens also manufactures a range of SITOP power supplies for use with many types of equipment including PLC'S.
SITOP Power Supplies



Chapter 15 we will discuss about ( Distributed I/O , System Configuration, PLC Tags , Monitoring values in CPU ) Topics ...

SIEMENS PLC Class for Beginners

Please Share this article, with your friends and colleagues


Comments

Popular posts from this blog

QElectro Tech Software Overview

Danfoss VLT micro drive FC 51 Name Plate

SIEMENS V20 VFD DRIVE FAULTS CODE LIST PART-1

SIEMENS V20 VFD DRIVE MAIN PARAMETERS LIST

Siemens RDG400KN Thermostat Parameter List