Siemens System Engineer Interview Questions, Process, and Tips

Round duration - 60 Minutes
Round difficulty - Medium

This round started with some questions from Programmable Logic Controllers or PLC followed by some basic questions from Intel 8051 Microcontroller.

Q1. Programmable Logic Controllers Question
What are the general functions of a PLC?
Ans. 
The functions of PLC are as follows:

1) Sequential Control: PLC processes binary signal input into output that is used for the purposes of sequential technical processing, here PLC keeps all steps in the sequential process in the right order.

2) Plant Monitoring: PLC continuously monitors the status of a system and takes the necessary actions in connection with the process being controlled or displaying the message to th...read more
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Q2. Programmable Logic Controllers Question
Describe about basic elements in Ladder logic programming .
Ans. 
There are three basic organizational elements associated with ladder logic:

1) RUNG: Ladder logic instructions are written on a function. During the scan program, the processor scans from left to right, one by one ladder from top to bottom.

2) INSTRUCTION: Ladder logic Instruction is divided into 2 parts;
2.1) Input instructions:
2.2) Displayed on the left side of the ladder Check, comparison, or specific conditions
2.3) Ou...read more
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Q3. Programmable Logic Controllers Question
What are the differnet types of PLC inputs & outputs ?
Ans. 
Inputs:

1) DC Inputs: DC input modules allow to connect either PNP (sourcing) or NPN (sinking) transistor type devices to them.

2) AC Inputs: There is no polarized AC voltage. The AC voltage is most frequently shifted via a limit switch or other form of switch.


Outputs:

1) Relay Outputs: One of the most common types of outputs available is the relay output. Existence of relays as outputs makes it easier to connect with ext...read more
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Q4. Programmable Logic Controllers Question
What are the advantages and disadvantages of S7 controller?
Ans. 
Advantage : cost, size, significant capability, multiple hardware options, controls S & G drives via profinet or profibus or analog/digital - whichever you like.

Disadvantage : limited I/O bandwidth, local I/O max of 8 modules, can't use a lot of the existing work done for s7-300/400 in STL, processing speed - but getting even a large project to run under 10 ms scan time is common.
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Q5. Programmable Logic Controllers Question
Explain The Time Stamp Available In S7-200 Plc .
Ans. 
This warning message indicates that the timestamps for the project do not match the timestamps for the program in the PLC. This may indicate that the programs are different, in which case it would be dangerous to continue the current operation. However, the programs may be functionally identical and still have different timestamps.
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Q6. Microcontrollers Question
Explain Jnc.
Ans. 
It is a command used to jump if no carry occurs after an arithmetic operation. It is called as jump if no carry (conditional jump instruction). Here the carry flag bit in PSW register is used to make decision. The processor looks at the carry flag to see if it is raised or not.
If carry flag is 0, CPU fetches instructions from the address of the label.
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Q7. Microcontrollers Question
What Are The Types Of Interrupts In Intel 8051 Microcontroller?
Ans. 
1) External interrupt 0 (IE0) has highest priority among interrupts.
2) Timer interrupt 0 (TF0)
3) External interrupt 1 (IE1)
4) Timer interrupt 1 (TF1) has lowest priority among other interrupts.
5) Serial port Interrupt
6) Reset.
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Round duration - 50 Minutes
Round difficulty - Medium

This round was heavily inclined towards Operating System and Computer Networks and the interviewer asked questions revolving around the fundamentals of the subject.

Q1. OS Question
What is a bootstrap program in OS?
Ans. 
It is generally a program that initializes OS during startup i.e., first code that is executed whenever computer system startups. OS is loaded through a bootstrapping process or program commonly known as booting. Overall OS only depends on the bootstrap program to perform and work correctly. It is fully stored in boot blocks at a fixed location on the disk. It also locates the kernel and loads it into the main memory a
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Q2. OS Question
Explain demand paging?
Ans. 
Demand paging is a method that loads pages into memory on demand. This method is mostly used in virtual memory. In this, a page is only brought into memory when a location on that particular page is referenced during execution. The following steps are generally followed:

1) Attempt to access the page.
2) If the page is valid (in memory) then continue processing instructions as normal.
3) If a page is invalid then a page-f...read more
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Q3. OS Question
What do chmod, chown, chgrp commands do?
Ans. 
These are file management commands. These are used for:

chmod - It changes the permission set of a file
chown - It changes the ownership of the file.
chgrp - It changes the group of the file.

Example :
$ chmod g+w test
It changes permission for a user group to write.

$ chown adas1923 testfile
It changes the owner of testfile to adas1923.

$ chgrp moderators testfile
It changes a group of testfile to moderators.
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Q4. OS Question
Explain any 5 essential UNIX commands .
Ans. 
1) ls -> Lists files in current directory
2) cd -> Change directory to tempdir
3) mkdir -> Make a directory called graphics
4) rmdir -> Remove directory (must be empty)
5) cp -> Copy file into directory
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Q5. Computer Networks Question
What are the different types of VPN?
Ans. 
Few types of VPN are:

1) Access VPN: Access VPN is used to provide connectivity to remote mobile users and telecommuters. It serves as an alternative to dial-up connections or ISDN (Integrated Services Digital Network) connections. It is a low-cost solution and provides a wide range of connectivity.

2) Site-to-Site VPN: A Site-to-Site or Router-to-Router VPN is commonly used in large companies having branches in differen...read more
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Q6. Computer Networks Question
Describe the OSI Reference Model
Ans. 
Open System Interconnections (OSI) is a network architecture model based on the ISO standards. It is called the OSI model as it deals with connecting the systems that are open for communication with other systems.

The OSI model has seven layers. The principles used to arrive at the seven layers can be summarized briefly as below:

1) Create a new layer if a different abstraction is needed.
2) Each layer should have a well-...read more
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Q7. Computer Networks Question
Explain TCP and UDP protocol.
Ans. 
TCP : TCP or TCP/IP is the Transmission Control Protocol/Internet Protocol. It is a set of rules that decides how a computer connects to the Internet and how to transmit the data over the network. It creates a virtual network when more than one computer is connected to the network and uses the three ways handshake model to establish the connection which makes it more reliable.



UDP : UDP is the User Datagram Protocol and...read more
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my
role.

Q1. Basic HR Question
Tell me something not there in your resume.
Ans. 
If you get this question, it's an opportunity to choose the most compelling information to share that is not obvious from
your resume.

Example :

Strength -> I believe that my greatest strength is the ability to solve problems quickly and efficiently, which makes me
unique from others.

Abillity to Handle Pressure -> I enjoy working under pressure because I believe it helps me grow and become more
efficient .


Tip : Emphas...read more
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