| AC |
Alternating Current. Current that periodically reverses direction. |
| analog input and output (I/O) channels |
I/O channels that connect to analog I/O devices. Analog channels use varying voltage or current signals. |
| analog input device |
A device that provides a variable current or voltage, such as 4 to 20 milliamps or 0 to 10 volts, representing a condition in a machine or process. An analog input device provides its signal to an analog input signal channel. |
| analog output device |
A device that is provided a variable current or voltage, such as 4 to 20 milliamps or 0 to 10 volts, representing a condition in a machine or process. An analog output device receives its signal from an analog output signal channel. |
| AS-i |
AS-Interface. AS-Interface is an open, low-cost field bus network endorsed by the AS-International Association that simplifies the interconnection of actuators and sensors. |
| AS-Interface |
AS-i. AS-Interface is an open, low-cost field bus network endorsed by the AS-International Association that simplifies the interconnection of actuators and sensors. |
| battery board |
A device that can be installed in an S7-1200 CPU to provide long term backup for the CPU’s real-time clock. |
| bit logic instructions |
A category of instructions in the FBD and LAD programming languages that perform logical operations using single bit memory locations. |
| bit memory |
Part of the global memory of a PLC that incudes binary bits that are available for use by any program block. |
| boolean logic |
A type of logic that uses logical functions such as OR, AND, and NOT. |
| communication modules |
Modules that allow a PLC to communicate with other devices through one or more communication ports on the module. |
| communications board |
A device that can be installed in an S7-1200 CPU to provide a serial communication port. |
| CPU |
Central Processing Unit. The brains of the PLC. The CPU stores and scans the user program and stores data needed by the user program and other devices and systems. |
| CTD |
Count down counter. An IEC counter instruction that counts down by 1 when the count down parameter (CD) transitions from 0 to 1. |
| CTU |
Count up counter. An IEC counter instruction that counts up by 1 when the count up parameter (CU) transitions from 0 to 1. |
| CTUD |
Count up and down counter. An IEC counter instruction that counts up by 1 on a 0 to 1 transition of CU and counts down by 1 on a 0 to 1 transition of CD. |
| data block |
DB. Each DB is an organized set of data in a Siemens PLC program that is used by one or more program blocks. An instance DB stores data for use by one program block. A global data block contains data that is available to any program block. |
| data type |
A classification that identifies how data in a memory location is interpreted. There are a variety of data types and they are often represented by shorthand names such as Int for a 16-bit signed integer or Real for 32-bit floating point values. |
| DB |
Data Block. An organized set of data in a Siemens PLC program that is used by one or more program blocks. An instance DB stores data for use by one program block. A global data block contains data that is available to any program block. |
| DC |
Direct Current. Current that flows in one direction. |
| digital input and output (I/O) channels |
I/O channels that connect to discrete I/O devices. Digital channels use signals that are either on or off. |
| DIN rail |
A 35 millimeter mounting rail for control components and related devices. |
| discrete input devices |
Devices that provide an on or off signal to a PLC through digital input channels. |
| discrete output devices |
Devices that turn on or off in response to signals from digital output channels. |
| duty cycle |
The amount of time that a signal or device is on, usually expressed as a percentage. |
| FBD |
Function block diagram programming. A graphical programming language defined in part 3 of the IEC 61131 standard. |
| fieldbuses |
Industrial networks used for distributed control communication. |
| function block diagram |
FBD. A graphical programming language defined in part 3 of the IEC 61131 standard. |
| general packet radio service |
GPRS. A cellular communication service that, when applied to PLC communication, can be used for wireless machine-to-machine control or remote data acquisition. |
| global memory |
Memory areas such as image tables and bit memory that are accessible to all program blocks in the user program. |
| GPRS |
General Packed Radio Service. A cellular communication service that, when applied to PLC communication, can be used for wireless machine-to-machine control or remote data acquisition. |
| HMI |
Human machine interface. A device or system that displays machine or process information and provides a means for entering control information. |
| human machine interface |
HMI. A device or system that displays machine or process information and provides a means for entering control information. |
| I/O |
Input/Output. Refers to a device, channel, or module involved with PLC inputs and/or output |
| I/O points |
Digital input/output points. |
| IEC 61131 |
A standard of the International Electrotechical Commission that provides common approaches and concepts for PLCs. Part three of the standard describes the programming language available for PLCs. |
| image tables |
Tables in a PLC CPU memory that store the most recent input and output status conditions. A binary 1 represents an on condition and a binary 0 represents an off condition. |
| incremental encoder |
A device that creates a pulse for each incremental change in the angular position of a shaft. A module can be added to SIMATIC S7-1500 CPUs that will measure using an incremental encoder. |
| industrial ethernet |
A type of Ethernet local area network that is widely used for computer and control system communication in factories and other industrial environments. |
| input/output |
I/O. Refers to a device, channel, or module involved with PLC inputs and/or outputs. |
| LAD |
Ladder diagram. A graphical programming language defined in part 3 of the IEC 61131-3 standard. |
| ladder diagram |
LAD. A graphical programming language defined in part 3 of the IEC 61131-3 standard. |
| LED |
Light emitting diode. An indicator light made from semiconductor material. |
| linear topology |
A network configuration in which devices are connected one after the other. In a PROFIBUS system, the master is connected to the slave devices by a linear topology. |
| load memory |
Non-volatile storage for the user program, program data, and configuration information. |
| master-slave system |
A computer networking communication protocol in which the master device controls communication. Slave devices respond to communication requests from the master device. |
| Mbyte |
1024 x 1024 bytes. Approximately 1 million bytes. Each byte is 8 consecutive bits. |
| non-volatile |
Used to describe a type of memory that does not require continual application of power to prevent data loss. |
| PID Control |
Proportional-integral-derivative control. One of the most common types of process control. PID control adjusts system outputs by reacting to three values, one that is proportional to an error, one that represents the error over time, and one that represents the rate of change of the error. |
| PROFIBUS DP |
PROFIBUS DP is an open standard fieldbus of PROFIBUS & PROFINET International (PI) that is widely used for master-slave control communications in factory automation. |
| PROFINET |
The open Industrial Ethernet standard of PROFIBUS & PROFINET International (PI), and the leading Industrial Ethernet standard world-wide. |
| program block |
A grouping of PLC instructions. A Siemens PLC can have three types of program blocks: organization blocks (OBs), function blocks (FBs), and functions (FCs). |
| proportional-integral-derivative control |
PID control. One of the most common types of process control. PID control adjusts system outputs by reacting to three values, one that is proportional to an error, one that represents the error over time, and one that represents the rate of change of the error. |
| real-time clock |
A circuit in a PLC’s CPU that keeps accurate track of time. |
| resistance temperature detector |
RTD. A temperature sensor made from a metal such as platinum, nickel, or copper that varies in resistance in a predictable manner as temperature varies. |
| retentive memory |
Non-volatile storage for a limited quantity of work memory values during power loss. |
| RTD |
Resistance Temperature Device. A temperature sensor made from a metal such as platinum, nickel, or copper that varies in resistance in a predictable manner as temperature varies. |
| RUN mode |
One of three modes of operation for an S7-1200 PLC. In the RUN mode, the CPU executes the PLC scan repeatedly. |
| scan |
A repetitive process performed by a PLC CPU that includes updating input statuses, executing the user program, updating outputs, and other important tasks. |
| SCL |
Structured control language. A high level programming language, also known as structured text. SCL is suitable for high-speed programming of complex algorithms and arithmetic functions. |
| servo motor |
A type of electric motor often used in precision motion control applications. |
| short message service |
SMS. Short Message Service is a text messaging capability used for telephone and computer communications. |
| signal board |
A device that can be installed in an S7-1200 CPU to add a small number of additional digital or analog I/O channels to the CPU. |
| signal module |
Also called an I/O module. A module that connects a PLC to input and/or output devices. |
| SMS |
Short message service. SMS is a text messaging capability used for telephone and computer communications. |
| STARTUP Mode |
One of three modes of operation for an S7-1200 PLC. In the STARTUP mode, the CPU executes any startup logic, if present. |
| STEP 7 Basic (TIA Portal) |
Engineering software used for the configuration and programming of SIMATIC S7-1200 PLCs and related devices. |
| STEP 7 Professional (TIA Portal) |
Engineering software used for the configuration and programming of SIMATIC S7-300, S7-400, S7-1200, and S7-1500 PLCs and related devices |
| stepper motor |
A type of electric motor often used for basic positioning applications that rotates in incremental steps. |
| STOP Mode |
One of three modes of operation for an S7-1200 PLC. In the STOP mode, the CPU is not executing the user program. |
| structured control language |
SCL. A high level programming language, also known as structured text. SCL is suitable for high-speed programming of complex algorithms and arithmetic functions. |
| structured text |
A high level programming language, also known as structured control language or SCL. SCL is suitable for high-speed programming of complex algorithms and arithmetic functions. |
| telecontrol |
A capability that enables centralized, remote monitoring and control of automation systems through a telephone network. |
| teleservice |
A capability that enables the exchange of information through a telephone network with remote automation systems for the purpose of fault detection, diagnostics, and maintenance. |
| thermocouple |
A temperature sensor made from two dissimilar metals joined at a point called a junction. A thermocouple produces a small voltage that is temperature dependent. |
| TIA Portal |
Siemens Totally Integrated Automation Portal. Software used for designing, commissioning, operating, maintaining, and upgrading automation systems. |
| volatile |
Used to describe a type of memory that requires continual application of power to prevent data loss. |
| web server |
A computer or software that allows information to be displayed using standard Internet protocols. |
| work memory |
Volatile storage for some elements of the user program. |