Basic Simulation Interview Questions & Answers

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Basic Simulation Interview Questions & Answers

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Basic Simulation Interview Questions

Basic Simulation Interview Questions
    1. Question 1. What Is Simulation?

      Answer :

      Simulation is the imitation of some real thing, state of affairs or process. In health professions education, simulation is a methodology to help achieve educational goals. Healthcare simulation encompasses a range of activities that share a broad but common purpose: To improve the safety, effectiveness and efficiency of healthcare services.

    2. Question 2. What Is A Simulationist?

      Answer :

      A simulationist is an expert in the knowledge, skills and attitudinal aspects of using the methodologies of simulation to achieve learning objectives.

    3. Question 3. What Is A Simulation Centre?

      Answer :

      A simulation centre is a physical space where simulation is employed for health professions education. Simulation activities can include technical skills training (manikins, task trainers), role playing, virtual reality/e-learning and blended simulation.

    4. Question 4. What Is The Need For Simulation?

      Answer :

      The Need for Simulation : 

      A simulator is a collection of hardware and software systems which are used to mimic the behaviour of some entity or phenomenon. Typically, the entity or phenomenon being simulated is from the domain of the tangible ranging from the operation of integrated circuits to behaviour of a light aircraft during wind sheer.

      Simulators may also be used to analyze and verify theoretical models which may be too difficult to grasp from a purely conceptual level. Such phenomenon range from examination of black holes to the study of highly abstract models of computation. As such, simulators provide a crucial role in both industry and academia.

      Despite the increasing recognition of simulators as a viable and necessary research tool, one must constantly be aware of the potential problems which simulators may introduce. Many of the problems are related to the computational limitations of existing hardware platforms but are quickly being overcome as more powerful platforms are introduced. Other problems, unfortunately, are inherent within simulators and are related to the complexity associated with the systems being simulated. 

    5. Question 5. What Is The Classification Of Simulation Systems?

      Answer :

      It is useful to classify the system being simulated into two separate categories depending upon the degree of randomness associated with the behaviour of the system in its simulated environment.

      For example, consider a simulated system consisting of a series of bank tellers who must provide transaction services to incoming customers. The length of time required for a teller to process a customer's transaction cannot usually be predetermined before the simulation is started. Consequently such a simulation system must introduce random behaviour to simulate the duration of each transaction.

      During the analysis of a real world banking system it may be discovered that the time required for a transaction occurs over some well known probability distribution. Hence the duration of each transaction may be generated from this distribution. A similar strategy may be adopted for the rate at which customers enter a bank. Through the introduction of this randomness, the results of a simulation may never be the same as a previous simulation.

      A system, such as this one, that relies heavily upon random behaviour is referred to as a stochastic system. The results generated from a stochastic system are typically analyzed statistically in order to make conclusions regarding the behaviour of the system.

      Conversely, a deterministic simulation system incorporates absolutely no random behaviour whatsoever. As such, the simulation results for a given set of inputs will always be identical. Simulations involving circuit behaviour are examples of deterministic systems.

      Supplying high signals to both inputs of a 2-input NAND gate will always produce a low signal on the gate's output, regardless of where the gate is located in the circuit's design hierarchy or when the inputs are received by the gate. In the context of circuit simulation, deterministic simulation is used to verify that a particular circuit design is behaving as expected  when the circuit is supplied with a given set of inputs, the circuit produces the expected outputs at the correct time. Although this report will focus primarily upon deterministic simulation systems, stochastic systems can also be simulated with modest modifications to the implementation.

    6. Question 6. What Are Simulation Models?

      Answer :

      Simulation Models : During the design and implementation of a simulator, various techniques and strategies may be adopted to model the behaviour of a given system. Depending upon the system to be simulated, some techniques may be more favourable than others. Factors including the level of abstraction and the desired accuracy and speed of the simulation should be taken into consideration when designing the simulator engine. Traditionally, simulators are designed using either continuous or discrete-event techniques to simulate a given system.

    7. Question 7. What Are The Abstraction Levels For Circuit Simulation?

      Answer :

      Abstraction Levels for Circuit Simulation : This report will describe the design and implementation of a digital circuit simulator. Consequently, this section will outline some of the aspects related to the simulation of circuits, including the different levels at which circuit simulators may operate.

      Circuit simulation provides a means of modelling a circuit's response to a given set of inputs. The simulator may generate numbers representing the voltages present at specific nodes of the circuit at certain times or it may generate waveform diagrams that show the circuit's output over the duration of the simulation. What is actually produced as a result of the simulation is largely dependent upon the abstraction level at which the circuit was described and subsequently simulated.

      For example, simulating a circuit described in terms of transistors and capacitors will conventionally show how these components interact at the electrical or analog level, whereas simulating a circuit described in terms of gates, flip-flops and registers will demonstrate the digital interaction amongst the components.

      Circuits may be described and simulated at several levels of abstraction. This section will describe three major abstraction levels, each of which are related to the simulation models described above. These levels are described below in order of increasing abstraction level.

    8. Question 8. What Are Circuit-level Simulators?

      Answer :

      Circuit-level simulators : Circuit-level simulators   are used to model the behaviour of a circuit at its lowest conceptual level. The circuit is described in terms of transistors, wires, capacitors and resistors and their respective interconnectivity. Circuit-level simulators manipulate extensive detail regarding the interaction of all the components in the circuit and also take into consideration subtleties such as wire resistance and geometric properties of the subcomponents.

      The end goal circuit level simulation is to produce very detailed analog waveforms which accurately model the behaviour of the circuit's devices in the real world. Consequently, continuous simulation techniques are often used to implement circuit-level simulators.

      Circuit-level simulations are typically performed in several stages. During the first stage, referred to as node-extraction, static analysis of the circuit description is performed. From this analysis, information regarding the circuit's devices, their respective attributes and their connectivity is obtained. This information is subsequently combined with modules known as device models that describe the behaviour of each device on a mathematical level. In order to model the circuit's behaviour, the simulator must then solve a system of differential linear equations which is derived from all the information supplied to it during the node-extraction phase.

      Although this method generates very accurate results, the technique is very computationally intensive, resulting in poor simulation speed. As a result, circuit-level simulation is usually not feasible for large designs and is therefore commonly used to simulate only the most critical subregions of a given circuit.

    9. Question 9. What Are Logical Level Simulators?

      Answer :

      Logic-level Simulators :  Logic-level simulators attempt to remedy the computationally intensive nature of circuit-level simulators by raising the level of abstraction to the domain of switches and logic components. Instead of manipulating continuous, analog data, logic-level simulators simply process logic values; that is, 0, 1 and X. In addition, logic-level simulators traditionally simplify the simulation process by assuming that the connecting wires have negligible resistance.

      Logic level simulators can be subdivided into two further categories, switch-level and gate-level simulators. In switch-level simulators, transistors are promoted to elementary switches and very little attention is given to the intricacies of other transistor attributes. During the simulation itself, equations governing the behaviour of the circuit are greatly approximated, thereby increasing the speed at which the simulator operates. The detail that is inevitably lost as a result of this approach is not usually vital.

      Gate-level simulators operate at yet a higher abstraction level. Low level circuit devices such as transistors, capacitors and resistors are replaced with logic gates such as NAND, XOR and flip-flops. Circuits described at this level bear strong resemblance to data flow diagrams in which information is passed amongst interconnected components.

      Effective use of logic gates permit relatively high-level designs to be easily described and subsequently simulated. Because the components are increasingly abstract, more complex systems may be designed and simulated at the gate level rather than at the switch level. Traditional gate-level simulators are implemented using discrete-event simulation; as such, this report will primarily focus upon circuits described at the gate level.

      There have been several successful attempts to merge switch-level simulators with simulators that operate at the gate-level and above, thereby allowing the designer to have the flexibility and speed of high-level simulators, while at the same time retaining some of the accuracy associated with switch-level simulators.

    10. Question 10. What Are Functional- And Behavioural-level Simulators?

      Answer :

      Functional- and Behavioural-level Simulators : Functional- and behavioural-level description languages and simulators represent the highest levels of simulation available to circuit designers. These levels enable designers to model circuits in terms of interacting abstract units that may not even be capable of fabrication.

      As such, designers are not limited by the restricted behaviour of fundamental circuit devices. In addition, these levels also provide designers a viable means of quickly exploring alternatives without becoming overwhelmed with the impact that design decisions would have on the circuit at lower levels.

      Functional-level simulators are generally closer to the actual hardware representation than behaviour-level simulators. An abstract unit in a functional-level simulation would accept input and produce output just like its corresponding hardware component.

      However, more flexibility is permitted with respect to how the input is presented to the unit and how it is processed to produce output. For example, an adder at the gate-level may consist of several half-adders which adds to numbers by operating directly on their bits. The equivalent functional-level unit would simply take two integers and add them using arithmetic constructs available in the hardware description language.

      Behavioural-level simulators go one level higher and permit designers to model abstract control processing which may not be realizable in hardware. The purpose of these simulators is to give the designer a general overview of the design and to experiment with high-level alternatives. The usefulness of design tools and simulators that operate at this level has been the subject of debate due to the difficulty in translating such high level designs into compact, high-performance circuits.

      However, advances in silicon compilation have made the translation process easier and more efficient. In addition, high level simulators are still useful for rapid prototyping, even if the design is not actually physically fabricated. Rapid prototyping allow designers to study the feasibility of a high level design before actually delving into the tedious, low-level details such as placement and routing.

    11. Question 11. Explain The Simulator User Interface?

      Answer :

      The Simulator User Interface : The intuitiveness and robustness of the user interface used by a software application can strongly influence the productivity of the people using that application. This chapter focuses on the design and operation of a graphical user interface for a digital simulator engine. Details with respect to the chosen platform and implementation language will also be discussed and justified. In addition, some limitations of the GUI will be described and potential solutions to these restrictions will be presented.

    12. Question 12. What Are The Advantages And Disadvantages Of Simulation?

      Answer :

      Advantages of Simulation :

      One of the primary advantages of simulators is that they are able to provide users with practical feedback when designing real world systems. This allows the designer to determine the correctness and efficiency of a design before the system is actually constructed. Consequently, the user may explore the merits of alternative designs without actually physically building the systems. By investigating the effects of specific design decisions during the design phase rather than the construction phase, the overall cost of building the system diminishes significantly.

      Another benefit of simulators is that they permit system designers to study a problem at several different levels of abstraction. By approaching a system at a higher level of abstraction, the designer is better able to understand the behaviours and interactions of all the high level components within the system and is therefore better equipped to counteract the complexity of the overall system. This complexity may simply overwhelm the designer if the problem had been approached from a lower level. 

      Thirdly, simulators can be used as an effective means for teaching or demonstrating concepts to students. This is particularly true of simulators that make intelligent use of computer graphics and animation. Such simulators dynamically show the behaviour and relationship of all the simulated system's components, thereby providing the user with a meaningful understanding of the system's nature. Consider again, for example, a circuit simulator.

      Disadvantages of Simulation :

      Despite the advantages of simulation presented above, simulators, like most tools, do have their drawbacks. Many of these problems can be attributed to the computationally intensive processing required by some simulators. As a consequence, the results of the simulation may not be readily available after the simulation has started -- an event that may occur instantaneously in the real world may actually take hours to mimic in a simulated environment. 

      One of the ways of combating the aforementioned complexity is to introduce simplifying assumptions or heuristics into the simulator engine. While this technique can dramatically reduce the simulation time, it may also give its users a false sense of security regarding the accuracy of the simulation results.

      Another means of dealing with the computational complexity is to employ the hierarchical approach to design and simulation so as to permit the designer to operate at a higher level of design. However, this technique may introduce its own problems as well. By operating at too high an abstraction level, the designer may tend to oversimplify or even omit some of the lower level details of the system. If the level of abstraction is too high, then it may be impossible to actually build the device physically due to the lack of sufficiently detailed information within the design.

       

       

    13. Question 13. Explain Continuous Simulation?

      Answer :

      Continuous Simulation : Continuous simulators are characterized by the extensive use of mathematical formulae which describe how a simulated component responds when subjected to various conditions. For example, consider a circuit described at the transistor, resistor and capacitor level. The behaviour of all these components are well understood and are governed by several equations which describe their respective behaviours.

      A continuous simulator would apply those equations in the context of the components' environment and connectivity and produce a continuous graph which accurately reflects how the components would react if they were actually hooked up in reality. The graphs usually reflect the changes in the state of the system with respect to time; however, other relationships may also be demonstrated as well. Unfortunately, the mathematical equations employed by a continuous simulator can make the simulation very computationally intensive, especially in the presence of thousands of interconnected elements. As such, continuous simulators may be slow and are consequently only useful when simulating a relatively small number of components which are described at a low level of abstraction.

    14. Question 14. Explain Discrete-event Simulation?

      Answer :

      Discrete-Event Simulation : Discrete-event simulation is used to simulate components which normally operate at a higher level of abstraction than components simulated by continuous simulators. Within the context of discrete-event simulation, an event is defined as an incident which causes the system to change its state in some way. For example, a new event is created whenever a simulation component generates output.

      A succession of these events provide an effective dynamic model of the system being simulated. What separates discrete-event simulation from continuous simulation is the fact that the events in a discrete-event simulator can occur only during a distinct unit of time during the simulation -- events are not permitted to occur in between time units. Discrete event simulation is generally more popular than continuous simulation because it is usually faster while also providing a reasonably accurate approximation of a system's behaviour.

    15. Question 15. What Are The Windows In Simulator Gui?

      Answer :

      The simulator GUI employs two windows  the circuit editor window (also known as the main window) and the signal display window. Together, these two windows provide the necessary functionality which lets the user construct and simulate digital circuits.

    16. Question 16. List Some Open Source Circuit Simulator Software List?

      Answer :

      some open  source circuit simulator software list:

      Micro-Cap 10 – is another demo version circuit analyzer and simulator from Spectrum Soft. As they claim its a mixed mode digital/analog circuit simulator with an intuitive user interface, fast simulation and great performance. I haven’t tried this yet, so if you are interested try your own.

      PECS – is a free power electronics circuit simulator created by Richard Tymerski. You can download the various manuals and tutorials from the website before start using the simulation tool.

      Proteus – Prospice is a mixed mode, Spice based simulation tool from LabCenter. They have two versions, basic and advanced. Basic version is free which supports interactive simulation only while advanced supports a range of useful functions and features like graph based analysis which includes frequency, noise, distortion, fourier parameters etc.

      QUCS – Quite Universal Circuit Simulator is a free simulation software developed on GNU/Linux environment. Well this software really works on other operating systems such as Solaris, Apple Macintosh, Microsoft windows, FreeBSD, NetBSD etc. User can simulate large signal, small signal and noise behavior of the circuit using this simple circuit simulator.

      Solve Elec – is an electrical circuit simulator (free version) which is developed for Macintosh OS and Windows. It enables users to draw and analyse circuits (both electrical and electronic) functioning in direct current or alternating current, get formulas, verify equations, get equivalent circuits etc.

      XSpice – is developed as an extension to Spice 3 by Georgia Institute of Technology. It has code modelling feature which enables user to add new models.

      MultiSim – is a student version circuit simulation software from National instruments. As you know, student versions always comes with limited access. Still this is a great simulation tool for beginners in electronics. MultiSim, the circuit maker software enables you to capture circuits, create layouts, analyse circuits and simulation. Highlight features include exploring breadboard in 3D before lab assignment submission, create printed circuit boards (PCB) etc. Breadboard simulation is possible with Multisim circuit simulator.

      TopSpice – this is a demo version circuit simulator from Penzar. This electronic simulation tool is tailored to work with Windows only and its is compatible for Windows XP/Vista/7.  TopSpice is a mixed mode mixed signal digital,analog, behavioral simulation software. It offers both Pspice and Hspice compatible simulation of circuits.

      Circuit Simulator 1.5j – is a freeware circuit simulation tool. I have not used this tool or even attempted a try. I add this as a suggestion from a user in our forum. I think this is just basic tool with very basic functions, created for starter purpose. Use at your own risk.

      MacSpice – is a free circuit simulation software for Apple Macintosh users. This circuit simulation which is compatible for PowerPC and Intel architecture Apple Macintosh (MAC pc) computers is derived from Berkeley Spice 3f5 . This breadboard simulator can perform simulation ranging from a single resistor to an integrated circuit with thousands of devices and components packed together.

      5Spice – is a free analog circuit analysis and simulator with many great features which includes a user expandable library of Spice/Pspice models, save any number of analysis results, integrated graphing of simulation results, student level MOSFET IC design etc. The focus is emphasized on analog circuit analysis and design at component level. 5Spice is mainly designed for students and educators, rather than industry professionals. Latest version of 5spice is released on October 31st 2001 – v 1.65.

      NgSpice – one of the popular and widely used free, open source circuit simulator from Sourceforge. NgSpice is developed by a collective effort from its users and its code is based on 3 open source software packages:- known as:- Spice3f5 , Cider and Xspice. Ngspice is a part of gEDA project which is growing every day with suggestions from its users, development from its contributors, fixing bugs and approaching perfection. As its a collaborative project you can suggest improvement of the circuit simulator and be a part of the development team.

      GnuCap – is another open source project, developed as a general purpose circuit simulator. Known widely as GNU Circuit analysis package, this linux based circuit simulator performs various circuit analysis functions as dc and transient analysis, ac analysis etc. Developers have incorporated spice compatible model for MOSFET, BJT and Diode.

      CircuitLogix – this student version software from CircuitLogix enables you to perform analog, digital and mixed mode circuit analysis and simulation.  This SPICE simulation software provides 4000 devices on its student version which is 1/3 of the pro version. This circuit building software give access to switches, linear IC and digital IC, FET, Transistors, relays, displays, signal generators, SCR’s, opto isolators, photo diodes, semiconductors, motors etc.

      LTSpice – is a widely popular SPICE simulator from Linear. LTspice is a free circuit simulation tool from Linear Technology corporation. This simulation software is considered as one of the best freeware available. Highlight of LTspice is much fast simulation of switching regulators with enhanced SPICE (compared to normal SPICE simulators).LTspice gives access to over 200 op amp models, transistor models, MOSFET models etc. A high disadvantage of LTspice is its proprietary code base which is licensed by Linear Technology. Had they made it open source, LTspice could have gone places with collaborative development.

    17. Question 17. Can I Use The Simulator Software Online With Just My Web Browser?

      Answer :

      No. The simulators are desktop applications that must be installed on your PC and used with simulator controls that are connected to the same PC. Only in this way can they deliver the real-time performance that's required to simulate the behavior of real heavy equipment.

    18. Question 18. What Is Usb?

      Answer :

      USB is a communication protocol used to connect a range of devices to a computer. USB "game controller" joysticks are plug-and-play with most versions of Microsoft Windows Operating Systems. Plug-and-play capabilities should be verified in Windows "Game Controller" utility.

    19. Question 19. Why Is Throttle And Rudder Automatically Increasing / Decreasing?

      Answer :

      If you are using the Throttle Quadrant or Pro Throttle with any CH yokes or joysticks,  you will need to disable all throttle assignments on the yoke or joystick inside your Flight Simulator.

      If you are using the Eclipse Yoke and Pro Pedals together, you will need to disable the Rudder, or Z Axis on the Eclipse Yoke inside your Flight Simulator.

    20. Question 20. What Are The Differences Between Carsim, Trucksim And, Bikesim?

      Answer :

      CarSim contains math models to simulate passenger vehicles and light trucks (i.e. pickup trucks and small utility vehicles). These math models contain equations for two-axle lead units as well as a single trailer with one or two axles. Dual tires in CarSim are not currently supported.

      TruckSim contains math models to simulate a range of vehicles from light trucks to commercial vehicles. Lead units can have up to five axles, one or two trailers are supported with up to four axles each, dual tires can be added to all axles, and all axles on the lead unit can be actively steered and driven. Additionally, TruckSim supports tandem and tridem axle load sharing as well as dollies to join multiple trailing units. There is also a TruckSim license module that allows you access to math models capable of representing torsional frame flexibility and suspended cab mounts.

      BikeSim is a simulation tool specifically designed to simulate the dynamic behavior of motorcycles and scooters.

    21. Question 21. Does Your Software Support 64-bit Matlab/simulink?

      Answer :

      Yes. CarSim, TruckSim, and BikeSim math models can run with either 32-bit or 64-bit Matlab/Simulink. At this time, the CarSim DS and TruckSim DS Simulink models running with the Logitech G25/G27 wheel/pedals/shifter only support 32-bit Matlab/Simulink.

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