Design Requirements: Workstation Test System

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1 Design Requirements: Workstation Test System ECE Senior Sear April 16, 2010 By: Andrew Dunn & Holly Peterson Faculty Advisor: Bob Kressin Sponsor: Tim Figge, Agilent

2 Table of Contents Overview... 3 Statement of Problem... 4 Operational Description... 5 Requirements Specifications... 6 Design Deliverables Workstation Testing System User Manual Engineering Manual... 8 Preliary System Test Plan... 9 Implementation Appendix

3 Overview At the University of Colorado at Colorado Springs, all electrical and computer engineering students utilize the equipment found in Engineering room 229. This particular laboratory contains 20 workstations, each with a set of four instruments: a 100 MHz, four-channel oscilloscope, a +/- 20 V power supply, a 6 ½ digit digital multimeter, and a 20 MHz function/arbitrary waveform generator. Due to the large number of students using these workstations every semester, the equipment wears down and eventually malfunctions or even breaks. This presents a problem for any professor or instructor using this laboratory as a teaching tool. Often, due to the varying experience levels of the users, the equipment is unintentionally used improperly. Currently, if a station is malfunctioning, the professor/instructor must carry out a lengthy inspection to detere which instrument is failing. The professor/instructor informally observes the response of the equipment, checking actual performance against expectations. He or she may detere, for example, that the channel on the oscilloscope isn t operating properly, or that the power supply isn t able to fully output +20 volts. Some users do not know how to detere what is not working and, in their frustration, they stress the workstation further. In response to this problem, the ECE department wishes to create a standard testing procedure for the instruments within the ENGR 229 laboratory. To this end, a testing device will be designed and the procedures the testing system will carry out. The Workstation Test System (WTS) will be as simple to use as possible, so that the testing can completed as often as necessary. In the case of malfunctioning technology, the tester will print out and file a report generated by the system. The benefit, discovering malfunctioning devices quickly and efficiently, will improve the operation of the lab and the learning taking place therein. 3

Statement of Problem The ENGR 229 lab at UCCS contains basic equipment needed to power up and exae a wide variety of circuits built in different courses.

4 Statement of Problem The ENGR 229 lab at UCCS contains basic equipment needed to power up and exae a wide variety of circuits built in different courses. Unfortunately, students unfamiliar with its operation often stress this equipment. A simplified auditing process to guarantee that a workstation is fully functional at the beginning, middle, and end of each semester is necessary. Any professor, instructor, or student with any level of experience must be able to fully test the oscilloscope, multimeter, power supply, and function generator at each workstation (See Figure 1). After detering that an instrument is malfunctioning, a user will file a WTS report with the ECE Department, and the instrument manufacturer will then repair the faulty device under its warranty. Oscilloscope 54622D Power Supply E3630A Function Generator 33220A Multimeter 34401A Figure 1: Workstation in Lab 229 at UCCS. All devices are made by Agilent Technologies. The user will first thoroughly test the most important and heavily used of the four devices: the oscilloscope. Then the power supply will be tested: the instrument second most likely to fail after the oscilloscope. It is currently only necessary to test these two instruments, though it is required to have the capacity to test all four, and possibly equipment located in other laboratories in the ECE Department, in the future. In an audit of the 20 workstations contained in the laboratory, the volts per division, time scale, and offset functions were informally tested. A probe was connected from a channel to the probe compensation signal on the front panel, generating a signal used to test each of these functions. This procedure allowed for consistency across all the channels on each oscilloscope in the lab. The team observed the maximum, imum, and auto-scale values of each function, checking observed values against expected values. Out of the available 68 channels, five channels failed the tests, twenty-one channels behaved questionably, and four oscilloscopes had three or more questionable channels (for further details on these data, please refer to the appendix.) Repairing these faulty channels would instantly improve the experience of the students and professors who use the oscilloscope regularly. Workstation Channels Volts/div Timescale Offset Autoscale Questionable Failed Table 1 Summary of Informal Audit Results 4

Operational Description The primary test is that of the oscilloscope, to be followed by the power supply.

The power supply will need to be manually tested, but the directions for measurements will be provided through a liquid crystal display (LCD) to the user, e.g. Adjust the +20 V knob so there are 12 V supplied.

allow testing of all four devices. To prevent signal coupling, noise and creating a solid grounding system, a four layer PCB will be developed.

5 Operational Description The primary test is that of the oscilloscope, to be followed by the power supply. Working properly, the oscilloscope is an excellent tool for testing the waveform generator and, tentatively, the multimeter. The power supply will need to be manually tested, but the directions for measurements will be provided through a liquid crystal display (LCD) to the user, e.g. Adjust the +20 V knob so there are 12 V supplied. A printed circuit board (PCB) will be designed, and its firmware will initially include WTS procedures for testing the oscilloscope and the power supply, but later modifications to the firmware would allow testing of all four devices. To prevent signal coupling, noise and creating a solid grounding system, a four layer PCB will be developed. Additionally, they will design a power circuit to ensure that the WTS can properly handle the range of voltages and currents from the instruments. The team will choose the connectors (e.g. BNC, banana jack, coaxial BNC, etc.) used to attach the WTS to the different pieces of equipment. An on-board microcontroller will carry out the testing process and display test results through a series of LEDs and/or an LCD display. Error reports will be simple, easy to understand, and detailed enough to allow a user to easily report any problems. The system will also be able to export report data (e.g. Excel or MATLAB) to a PC through USB or to an SD card inserted into a card slot on the PCB. The completed WTS will be capable of fully testing two test instruments located at each workstation in the ENGR 229 laboratory and will be adaptable to accommodate other models of instruments (e.g. two different models of oscilloscope.) The entire testing circuit will be on the PCB and will have enough connectors for each piece of equipment, as well as a system power circuit for added efficiency. Once users can quickly and easily identify instruments that need warranty work, the reliability and usefulness of the lab as a whole will increase dramatically. Make Connections Oscilloscope and Supply to Workstation Test System Test Oscilloscope External and Internal Tests Detere if Testing can Continue Test Supply Internal Component and External Display Tests Report Results Generate Data File Provide User Feedback Figure 2 Overview of WTS 5

6 Requirements Specifications The requirements for the WTS can be divided into core and stretch goal categories. The following list details the core goals of the WTS: The capability to connect to and sufficiently the oscilloscope and the power supply. The expandability needed, via expansion header, to accept input from various other electronic instruments. A user interface capable of displaying pertinent testing process information. An LCD screen with simple, two line data output. An automated testing process for which an instruction manual will not be required; all relevant instructions will be clearly displayed on the WTS s screen. The ability to output data upon completion of testing tasks, accomplished by storing information to external flash memory (e.g. SD card, USB flash drive). A microcontroller capable enough to allow testing all four instruments. Self-powered system, independent of workstation instruments. Adequately complete a functionality and parametric testing plan. The following list details "stretch" goals that may not be reached but which would, however, improve the usability and performance of the WTS: A custom case that can support the system and protect it against heavy use. The capability to test all four instruments at a workstation. The capability to control devices which have self-calibration capabilities. A touch screen interface. A high resolution LCD (rather than a simplistic, two-line display). The required tests for the oscilloscope and power supply are outlined below. The order listed is tentative, merely one possible testing procedure. The oscilloscope tests are divided into internal system tests and front panel tests. The internal system tests audit the internal measurement circuitry while the front panel tests analyze the user input systems of the scope. 1 Connectivity Tests 1.1 Cables Properly Attached 2 Oscilloscope Tests (Each test is applied to all available channels.) 2.1 Internal Systems Internal Resistance /1 Div Relay /25 Div Relay Auto-Scale Trigger V/Div 2.2 Mechanical Knobs/Buttons (Front Panel) Auto-Scale V/Div Offset Timescale 3 Supply Tests 3.1 Ground/Common Tests Oscilloscope Reference WTS Reference 3.2 Display Tests Voltage Reading 6

3.1.2 Current Reading 3.1.3 Overload Notifier 3.3 +6V Rail Tests 3.2.1 Voltage 3.2.2 Current 3.4 +20V Rail Tests 3.3.1 Voltage 3.3.2 Current 3.5-20V Rail Tests 3.4.1 Voltage 3.4.2 Current All of these tests are managed by the microcontroller.

7 3.1.2 Current Reading Overload Notifier V Rail Tests Voltage Current V Rail Tests Voltage Current V Rail Tests Voltage Current All of these tests are managed by the microcontroller. Figure 2 displays the flow of information within the WTS s microcontroller. The WTS will have a physical layout similar to the one shown in Figure 2. Figure 2, however, is only an outline of all major physical device connections. Figure 3 Diagram of Information Flow within WTS 7

8 Design Deliverables 1. Workstation Testing System A. Proficiency in testing the oscilloscope and supply at each workstation. B. Expandability to analyze all test instruments at each workstation. C. Expandability to test other instruments found on campus. This will depend on the microcontroller, which will only support the number of devices for which there are available GPIO ports. D. Automation for ease of use. E. Detailed and understandable error reporting which will allow users to realize and easily report problems. 2. User Manual A. Will outline basic usage of the system. B. Will include detailed drawings of setup and configurations steps. C. Will use organized methodology for proper operation. D. Will include examples of expected results (both pass and fail). E. Will include instructions concerning usage of the information obtained from test(s). 3. Engineering Manual A. In depth explanations of design. B. Detailed descriptions of implementation. C. Discussion of firmware. D. All diagrams, designs, code and other documentation related to the technical aspect of the project. 8

9 Preliary System Test Plan 100% functionality of the WTS would be very difficult to ensure. By using two test schemes, however, it is possible: there are two instruments at the workbench that will be tested by the WTS, each with its own testable characteristics and nuances. To ensure that the WTS is capable of testing the gross functionality of each instrument, the WTS will itself be tested in both a functionality and a parametric testing scenario. The required tests for the WTS are outlined below The functionality testing will implement testing known faulty oscilloscopes and power supplies against faultless instruments. This will ensure the WTS identifies testing equipment that doesn t operate flawlessly and correctly identifies what is not working through the scope of tests. The WTS must ensure analyze each individual instrument, perform the corresponding tests properly, give no false positives, and interfere with no other aspects of the testing process. While conducting the functionality testing, manual testing records will be kept and used to modify the firmware for further accuracy. Repeating these tests on multiple workstations will not only verify the proper operation of the WTS, but will also demonstrate the reliable and simple capability of the WTS. In addition to this functionality test, the WTS will be subject to various levels of parametric testing. These tests will check the WTS s ability to collect parametric data, interpret it properly, and present the user with accurate, relevant information. A stress test will be conducted on the WTS, wherein it will be pushed it to its limit with relation to the power supply. Since the power supply is an output rather than a measurement device, the WTS must interpret the yield of the supply, testing its voltage and current. Additional equipment will be necessary to perform the parametric testing. 1 Connectivity Tests 1.1 Cables Properly Attached 2 Functionality Testing 2.1 Oscillscope Front End Internal Acquisition Front Panel 2.2 Power Supply Ground/Common Tests Display Tests Rail Tests 3 Parametric Testing 3.1 Ability to Collect Data 3.2 Ability to Analyze Data Correctly 3.3 Status Passed to User & Accuracy 3.4 Stress Test 9

10 Implementation There are several implementation considerations inherent in the WTS s design: 1. A high usage system requires robust components and design. 2. Reprogramg will require a firmware upgradeable platform. 3. Expandability will require physical design considerations. 4. Power supply requirements will require physical design considerations. 5. The system must have data storage and transmission capabilities. 6. The native on-board code must be accessible and modifiable. 7. Maintenance on the completed system should be imal. 8. The high use of the mechanical components (e.g. hot-swapping of cables) requires the WTS to protect against electro-static discharge. 10

11 Appendix Informal Audit Results Workstation # max auto Channel 1 Times cale Max Timesc ale Min Timesc ale Auto 1 X X X X X 2?? X X 3? 4???? 5?? 6? 7?????? ?? * 15 M ax D C mi n atu o *Autoscale failed to follow signal to channel 2, 3, 4 Workstations performed acceptably, but with variances on Autoscale, as most of the oscilloscopes did. Worksta tion # V/di v max auto Channel 2 Max X X?? 4?? 5?? 6???? 7???? 8?? 9 10?? X X 13 14*?? atuo 11

12 15?? Worksta tion # max 1 2 3?? ?? 14* 15 Worksta tion # max auto Channel 3 Max Channel 4 auto Max ??? 5 6??? 7?? 8?? 9 10???? X X 14* 15?? atuo atuo 12

Agilent 3630A Triple DC Power Supply. Agilent 34401A Digital Multimeter (DMM)

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