91638 Sample Specific Assessment Guide - NZQA

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Level 3 Digital Technologies 91638 (3.47)
Specific Assessment Guide
Title Demonstrate understanding of complex concepts used in the design and construction of electronic environments

Credits 4

Teacher introductionTechnology assessment guides have been produced to help teachers develop their own specific assessment guides. Examples of specific assessment guides, developed from the common assessment guide for each standard, have been produced as part of the external assessment resources for level 3 Technology.
The specific assessment guides also show a variety of ways (ie, case study, research, practice) to produce external assessment material. The material in the candidate exemplars for each standard reflects the content and context of the specific assessment guides.
Teachers can adapt a common assessment guide and / or a specific assessment guide to suit the specific context of their course of teaching.
A model elevator is used as the context for learning in the assessment exemplars for this standard. This does not imply that this is the only context or method for assessing this achievement standard. The model elevator as an example here is used to assist candidates to gain and demonstrate an understanding of the complex hardware and software concepts relevant to the construction of electronic environments. This understanding could be gained and demonstrated in any appropriate context or contexts that incorporate complex concepts appropriate to this level of electronics and control.
The student report must demonstrate understanding of the selected concepts and adhere to the guidelines provided in the assessment specifications.
Candidate introductionYou will produce a report that demonstrates understanding of complex concepts used in the design and construction of electronic environments.
You are asked to develop an understanding of some complex hardware and software concepts and demonstrate clearly that you understand these concepts and how they are applied in a real-world context. This will require you to produce a report in which you can provide text and include schematics, diagrams, photos, graphics, etc if these assist your explanation.
One way of gaining understanding of both hardware and software concepts is to consider their application in an actual electronic environment. The exemplars produced from this guide take as their context (the electronic environment) the elevator, that is, a passenger lift that allows people to be moved between the different levels (floors) of a building. You could base your learning around investigating how a model elevator control module could be developed (both hardware and software), perhaps doing some functional modelling on a simulation programme or on breadboard. In this way, you could, if you wished to continue with the elevator context, extend and apply your understanding to functional modelling and prototyping of the elevator and access assessment opportunities for the complex interfacing standard 91639 (3.48) or the complex construction standard 91640 (3.49).
However, the elevator is just one possible scenario, and you are encouraged to consider other real-world contexts as you develop your understanding and appreciation of the concepts that enable electronic hardware and embedded software to be applied and to function together in electronic devices and installations. There are many possible such contexts, for example renewable energy (eg wind farms), environmental monitoring (eg weather stations), medical electronics (eg CAT and MRI scanning), and communications (eg. mobile phone technology).
Your selection of complex hardware and software concepts from the lists above will obviously depend on the context you choose (the electronic environment).
You may also consider adding in additional concepts not included in the lists in EN 5 and EN 6, for example oscillator circuits, power supplies (DC, AC, switch-mode), impedance matching, data compression, and communication protocols (eg I2C, RS232, etc).
Preparing the reportTo develop and demonstrate your understanding of complex concepts, it is suggested that you consider the following approach that will assist you to gather your evidence. The report itself is a summary of the experience and understanding you have gained during the learning phase.
1. Context selection. Select a context (an electronic environment eg a similar application to the elevator) that is an example of an application of electronics and control in the real world.
2. Research phase. Carry out an initial investigation into the context and in the process learn about the way the selected environment functions and how the hardware and software work together to enable control of the environment. This includes monitoring and correction strategies if the environment moves ‘out of spec’ or is subjected to external threats and stresses.
3. Concept selection phase. Identify both the hardware and software concepts that you will apply to the context. Clearly state these as general concepts (not just what the specific software or hardware does), for example for the model elevator one hardware concept might be the principle behind the operation of the DC motor interface (the H-bridge, etc), which embodies the concept of controlling current direction and power to a motor. One software concept might be the principle of software feedback using flags and / or interrupts for different situations that might arise during elevator operation, eg preventing the lift door closing on someone as they get in.
4. Evidence collection and research phase. This is the opportunity to investigate what might happen in different situations, eg for the model elevator, when different conditions arise. A simulation tool could be used here, or a control circuit (including a microcontroller) built and tested on a breadboard, or a survey of elevator function through studying actual control systems with the cooperation of an elevator company. Notes, diagrams, photos, etc could be collected and sorted at this stage. A literature or web search will also assist in expanding understanding of the selected concepts being studied.
Note: These exercises, which add to conceptual understanding, might be carried out as part of a holistic teaching and learning programme that also includes development of key skills, such as interfacing and construction.
5. Report writing phase. This is the time to organise all the evidence you have collected for your understanding of the concepts you have studied. Remember you are going to have to convince the external assessors that you actually understand these concepts, how they work, where they are applied in context and (for Excellence, go a lot further and discuss their application and limitations and compare and contrast to other examples in other contexts, for example to extend the elevator context, their application in escalators, conveyors, and so on).
Your report must be in your own words, to the point, and be drawn from a range of sources and your own experiences. Your report must also be relevant to the context you have chosen.
Candidate guidance for producing the reportThis assessment guide must be read along with the achievement standard and the assessment specifications.
The prompts provided below are guides to producing a report that demonstrates understanding of complex concepts used in the design and construction of electronic environments. The prompts guide candidates to produce evidence for all grades of the standard – Achievement, Merit, and Excellence. It is not necessary to respond to all prompts to succeed at any level. The later prompts guide candidates to in-depth discussion.
Each report will be assessed overall as to the level of understanding the report demonstrates of complex concepts used in the design and construction of electronic environments.
Your report should:
describe complex software concepts e.g. describing software flags used to show conditions within a program, such as indicating the status of a model train on a track
describe microcontrollers and other complex hardware concepts e.g. describing various feedback techniques in op-amp circuits
explain complex software concepts e.g. explaining how interrupts are used to suspend usual programme flow, such as when a second model train enters the same section of track as the first train
explain microcontrollers and other complex hardware concepts e.g. explaining how signals can be mixed such as audio in a summing op-amp circuit
discuss complex software concepts e.g. discussing why flags are selected for a programme, such as when handling requests from multiple sources in a model train system
discuss microcontrollers and other complex hardware concepts e.g. discussing why multiple stages of amplification rather than a single stage is more appropriate for a pressure sensor design.
The concepts that you can select for the purposes of your report must include both hardware and software concepts.
Suggested concepts are outlined in the achievement standard under explanatory notes 4 and 5.
Complex software concepts include a selection from:
structuring complex programs logically
analogue to digital and digital to analogue conversion
flags
counters
interrupts
bitwise logic (ie bitwise AND and OR statements)
idea of serial data transmission, baud rate using wires, Infra Red (IR), radio
Universal Serial Bus (USB)/Ethernet/Wireless Fidelity (WiFi) interfaces.
Complex hardware concepts include microcontrollers and a selection from:
effects of component tolerance in a circuit
effects of capacitor-resistor timing and idea of a time constant
system amplification
noise reduction and filtering
photodiode circuits
Liquid Crystal Display (LCD) displays
DC motor interface, either transistor or H-bridge with speed control
Op-amps (various purposes)
variable voltage regulators
Field Effect Transistors (FETs)
special function ICs eg 555 timer, 556 vco, DDS function generators
multiple sensors (typically some of the following: Hall effect sensor, strain gauge, pressure sensor, proximity sensors)
multiple actuators (typically some of the following: relay, DC motor, solenoid, servo, stepper)
CRYSTAL oscillators
RF circuits.
Essential documentsThe achievement standard governing this specific assessment guide can be found at HYPERLINK "http://www.nzqa.govt.nz/nqfdocs/ncea-resource/specifications/2013/level3/91638-spc-2013.pdf"http://www.nzqa.govt.nz/nqfdocs/ncea-resource/specifications/2013/level3/91638-spc-2013.pdf
The assessment specifications for the Technology achievement standard can be found at HYPERLINK "http://www.nzqa.govt.nz/nqfdocs/ncea-resource/achievements/2013/as91638.pdf"http://www.nzqa.govt.nz/nqfdocs/ncea-resource/achievements/2013/as91638.pdf
DefinitionsThe following definitions might be useful when you are writing your report.
Complex concepts are principles that explain the operation of electronic environments that apply to commercial electronic products (see the achievement standard for a list of these concepts).
Embedded software are programmes and variables stored in the restricted RAM or ROM memory space available in a microcontroller.
Structuring a programme is arranging and sequencing the programme (which could include a range of commands* ranging from simple to sophisticated) so that the programme is efficient (uses minimal memory space, is executed in real and minimal time, is acceptably responsive with respect to inputs and outputs) and logical (uses a command set that simplifies the code, is structured so that it flows, is formatted so that it can be readily understood, debugged and developed further).
* Commands used for code at the Achieved level will tend to be simple, code at the Merit level will include an extended range of commands, and code at the Excellence level will employ some specialised commands and strategies. The assessment exemplars will provide some guidance.
Microcontroller is a ‘computer-on-a-chip’; it has its own memory (ROM and RAM), can process instructions and data, and has input / output functionality.
Serial data is a way to transfer information by breaking the characters of a software ‘word’ into bits, which are then transmitted sequentially along a single line, one at a time.
Analogue is an input or output variable that has a continuous value, ie you can in principle define it to any number of decimal points.
Digital is an input or output value that is not continuous, ie there is a limit to its accuracy that depends on the number of bits used to define a single value.
Bitwise is an operation (AND, OR, XOR, etc) that deals with the individual bits and does not include a carry function.
Flag is a software or hardware mark that signals a particular condition or status. The programme is written to remember it and retrieve and act on it at the right moment. A flag is like a switch that can be either on or off. A flag is said to be set when it is turned on.
Interrupt is the programme is written to constantly check for interrupts, which are signals that instantly stop the normal execution of the programme and divert it to a subroutine, which deals with the ‘emergency’ and then resumes operation at the point in the programme where it left off.
Time constant is the product of R (resistance) and C (capacitance) in the circuit. This defines the reaction time of the circuit to a disturbance or input. One time constant is typically equal to approximately 63% of the total time of reaction.
Tolerance is the total allowance of error for a value or process, eg the tolerance in the resistance value of a resistor gives the designer a measurable confidence in the overall expected performance of a prototype or product.
LCD: Liquid crystal display is a low-power, flat-panel display used in many digital devices to display numbers or images.
FET: field-effect transistor is one that works by voltage control, rather than current control.
VCO: voltage-controlled oscillator is an oscillator (vibrator) whose frequency is controlled (modulated) by the voltage level at a point in the circuit.
RF: radio frequency is the range of frequencies of transmission between 104 to 1011 or 1012 Hz.
Further informationAppropriate reference information is available in:
Safety and Technology Education: A Guidance Manual for New Zealand Schools, Learning Media, Ministry of Education, 1998.
The Health and Safety in Employment Act 1992.
Technology Curriculum Support, October 2007 (found at  HYPERLINK "http://techlink.org.nz/curriculum-support/papers/knowledge/tech-systems/index.htm" http://techlink.org.nz/curriculum-support/papers/knowledge/tech-systems/index.htm).
Further information can be found at  HYPERLINK "http://www.techlink.org.nz" http://www.techlink.org.nz.
ExemplarsPlease read the exemplars. You can model your work on these exemplars but you may not copy the material from the exemplars. Your report must be the product of your own efforts.




Schedule
Assessment Schedule
AS Digital Technologies 91638 (3.47)
Demonstrate understanding of complex concepts used in the design and construction of electronic environmentsFinal grades will be decided using professional judgement based on a holistic examination of the evidence provided against the criteria.Issues from the Specifications
Authentic candidate submissions will be recognisable because of specific contexts associated with the work. This does not imply that submissions will arise only from the candidate’s practice. However, where the candidate’s practice does not provide the immediate source of a specific context, one would expect to see that several sources of information relating to materials had been applied within a specific context. In both cases, the marker will be able to detect the candidate’s voice. In situations where information does not have some aspect of student voice, it is difficult to establish whether the candidate has actually demonstrated understanding or simply identified information.
Candidates who have simply identified information by reproducing information from sources without making use of that information have not demonstrated understanding.
Where a candidate has provided a brief answer, the answer should not be penalised because of length.
Candidate work in excess of 14 pages should not be marked.
Where work is illegible, it cannot be marked.
Digital submissions that cannot be read cannot be marked.AchievementAchievement with MeritAchievement with ExcellenceDemonstrate understanding of complex concepts used in the design and construction of electronic environments involves:Demonstrate in-depth understanding of complex concepts used in the design and construction of electronic environments involves:Demonstrate comprehensive understanding of complex concepts used in the design and construction of electronic environments involves:describing complex software concepts e.g. describing software flags used to show conditions within a program, such as indicating the status of a model train on a track
describing microcontrollers and other complex hardware concepts e.g. describing various feedback techniques in op-amp circuits. explaining complex software concepts e.g. explaining how interrupts are used to suspend usual program flow, such as when a second model train enters the same section of track as the first train
explaining microcontrollers and other complex hardware concepts e.g. explaining how signals can be mixed such as audio in a summing op-amp circuit.discussing complex software concepts e.g. discussing why flags are selected for a program, such as when handling requests from multiple sources in a model train system
discussing microcontrollers and other complex hardware concepts e.g. discussing why multiple stage of amplification rather than a single stage is more appropriate for a pressure sensor design.








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