Shared Flashcard Set

Details

Phase 5 Final Exam
n/a
46
Aerospace Engineering
Professional
10/01/2012

Additional Aerospace Engineering Flashcards

 


 

Cards

Term
Describe how power supplies are applied to electronics.
Definition
Change available electrical energy to the form required by the circuits of the system.
Term
What are some power supply maintenance activities and systems that have shock hazards?
Definition
-Using M&TE
-Bench testing
-Removal/Installation on energized systems.
-ALL electronic systems have shock hazards.
Term
What are the termination points on a power supply used for?
Definition
-Ground
-Input - normally AC
-Output "+" and "-" - terminals connect the power supply to the load
-Sens + and - or sensing - Used for regulation and can be LOCAL or REMOTE. Used to minimize the effect of the output leads.
Term
Some power supplies offer several design options. What are they?
Definition
-D.C. Input - needed if the SUPPLY VOLTAGE is DC.(Ex: Sequencers and 7300)
-Alarm - terminals connect supply auxiliary relay contacts to an alarm system to communmicate power suplly failure.
-Power On Reset - is a pulse from the supply to the sytem and occurs when supply ouput is restored.
-Interlock - shuts down the supply when a circuit board is removed. After the board is reinstalled, a reset button is depressed to restore supply output.
-A.C. Output - provides AC output.
Term
How do you connect M&TE to a power supply?
Definition
-Vendor manual will describe requirements.
-NEVER use a decade box as a load.
-Output voltage is measured in parallel across load.
Term
What are the functions of available power supply adjustments?
Definition
-Voltage adjust - sets the desired output voltage. Can be local or remote.
-Current limit adjust - sets the point where current stops increasing by dropping output voltage. Makes power supply short circuit proof.(protects power supply)
Overvoltage protection adjust - sets the point where the supply will crowbar the ouput to zero.(Protects load)
Term
How do you restore supply output after an over-voltage condition?
Definition
Momentarily inerrupt supply input line voltage.
Term
How are converters used in process control applications?
Definition
-Provide an INTERFACE and/or ISOLATION between instruments that have incompatible signals.
-Protects upstream devices from downstream failures.
Term
How is M&TE connected to test/calibrate current and voltage converters?
Definition
-Preferred method is to read the voltage across a series resistor.
-Usually requires 2 DVMs. One at input and output with signal source.
Term
What are the two major components of current and voltage converters?
Definition
-Op Amp
-Resistor
Term
Explain the operation of current and voltage converters.
Definition
-The transmitted current(I) develops a voltage across resistor Ra that is proportional to the input current.
-This voltage is biased by the zero pot to take out the zero suppression.
This voltage is then sent to the op amp to produce a 0-10 VDC output.
Term
Calculate converter input/output values based on converter application.
Definition
4-20 mA = 0-10 VDC
10V/16mA - .625V/mA
Eout = (Iin x .625V/mA - 4 mA)
Term
What adjustments need to be made to calibrate a current or voltage converter?
Definition
-Zero and span.
-Normally fail with a zero output.
Term
Name and describe the types of position transmitters.
Definition
-Resolvers and Synchros - resolver has 2 stator windings 90 degrees apart and a synchro has 3 stator windings 120 degrees apart.
-Inductive Plates - essentially a resolver whose windings have been projected onto a linear medium.
-Pulse Position - use a grating and a photocell to produce pulses to an up/down counter to track position.
-Magnetic Pin or Tooth - used when position accuracy down to 0.00005 in. is req'd.
-Rotary Encoders - absolute and incremental provide output signals representative of shaft gearing rotation.
-LVDTs - magnetic iron core, moves axially within a cylindar which changes the voltages being induced in the secondary windings. (At 50% valve postion = 0 Vdc)
-Proximity Probe
Term
What are the major components of a position transmitter?
Definition
-Primary winding, opposing secondary windings and a moveable core.
Term
How are position transmitters used in the field?
Definition
-LVDTs-Case expansion on main turbine, throttle and governor valve actuator servo system feedback and modulating target rock valve acutator feedback. Output is converted to a +/-DC voltage with 50% valve position output typically at 0 VDC.
-Resolvers & Synchros-Shafts, gears and robot arms.
-Pulse Position Transmitters-Computer printers
-Potentiometers-Recorders, Viper Flow Scanner and MS/PORV Actuator
-Rotary Encoders-Absolute Encoders are used in the INCORE Drive Units.
Term
How do you connect M&TE and calibrate postion transmitters?
Definition
-Calibrated by positioning the shaft, table, arm, etc. to a zero reference position and then mechanically adjusting the position transmitter until its readout indicates zero.
-A resolver can also be zeroed by locking the gears in a zero reference position, connecting a DVM on volts AC function to the S1-S3 winding, and then turning the resolver case until the DVM reads 0 VAC.
Term
How do you connect M&TE and calibrate postion transmitters? (cont'd.)
Definition
-LVDT calibration is determined by the system, the work control document and scaling.
-The S/G PORV Actuators use a cylindrical dual element potentiometer as a position transmitter.
One element is for position feedback to the servo amp. The other is used to develop indication.
-The potentiometer pickup arm is mechanically adjusted to match calve stroke length.
Term
List five functions that electronic controllers perform.
Definition
-Location
-Signal Isolation
-Signal Conversion
-Signal Comparison
-Process Indication
Term
What are the functions of various controller adjustments?
Definition
-Gain Control Adjustment Knob - varies feedback voltage to gain amplifier.
-Integral/Reset Rate Adjustment Knob - Sets integral time, normally 5-200 sec.
-Derivative/Rate Adjusment Knob - Determines controller initial rate of response to a process change.
Term
Label the component parts of an electronic controller.
Definition
REFER TO SLIDE 18.
Term
What are the advantages of a digital controller?
Definition
-No potentiometers to adjust(drift does not occur).
-Digital display is more readable.
-No indicator needles to stick.
-Utilize contact outputs for alarms to be generated w/o use of instrumentation.
-Online diagnostics to monitor controller and loop health.
-Have MODBUS addressing to allow control of several controllers from one location.
-PB, Reset and rate are automatically adjusted.(Self-tuning)
Term
What are some disadvantages of a digital controller?
Definition
-D/A or A/D causes step changes due to their conversion method that can result in cycling the final control element.
-Loss of indicating display
-Affected by RFI(Radio frequency).
Term
How does the primary and secondary loop interact in a cascade control system?
Definition
-More than one control loop in Cascade.
-Primary(Master) loop regulates a controlled variable that is to be kept at a constant value and the second loop adjusts a second controlled variable that can cause fluctuations in the first controlled vaiable.
Term
What are some advantages of cascade control?
Definition
-Reduced disturbance effects.
-More precise automatic adjustment.
-Uses standard instrumentation.
-Minimal cost.
Term
What is a major characteristic of feedfoward control?
Definition
-Controlled variable is not used in determining the appropriate value for the manipulated variable.
Term
What is the purpose of using feedback trim in a feedforward control system?
Definition
-A problem with feed forward control is the change in parameters that affect the controlled variable and are not included in the energy balance equation.
-Feedback trim corrects heat and energy loss.
-Additional component for feedback trim is a temperature controller.
Term
What are two methods to compensate a digital controller and minimize its disadvantages?
Definition
-Controllers are designed with diagnostic software to monitor controller's performance.
-Fault tolerate control scheme.
Term
What precautions must be taken when working on controller that have a daisy chaned wiring scheme?
Definition
-Evaluate the effect on system and instrument prior to lifting leads. This type of wiring configuration is normally found on AC or DC supply voltages.
Term
Explain the operation of a programmable recorder.
Definition
-Handle a wide variety of inputs; including VDC, T/C, RTD and current.
-Can be calibrated using menu driven sequence via keyboard, operator display and vendor manual.
Term
What is the programming sequence to install point parameters and personalized features?
Definition
-Programming is required to establish range and span data, define functions, and personalize features.
-Manuals provide a HOW TO flowchart and parameters are stored in EEPROM or non-volatile memory.
Term
What are the steps to calibrate a programmable recorder.
Definition
-Vendor manual and a presicion voltage source is req'd for most calibrations.
-ZERO and SPAN may or may not be used.
Term
What are LOG functions?
Definition
-Initiated printouts.
-3 categories: Normal Operation, System and Program.
Term
What are some troubleshooting techniques specific to programmable recorders?
Definition
-Error message display
-Diagnostic test can be run when power is turned on or through the menu.
Term
Explain the design, construction and operation of a non-programmable recorder.
Definition
-Zero and Span pots
-Analog input, print drive and chart drive.
Term
Describe how to calibrate a non-programmable recorder.
Definition
-Apply input value, compare with output. Calibrate per vendor manual.
Term
What are the hazards associated with analytical instruments?
Definition
-Chemical exposure, temp, pressure, radiological, reagents.
Term
Name the types of analyzers at STP.
Definition
-In-line or bench top.
-Hydrogen, Chlorine, Hydrazine, Gas Chromatographs, Boron, Moisture, Sodium, Silica, Hardness, Oxygen, Conductivity, pH and ORP.
Term
How does an analytical instrument work?
Definition
-Observes the consequences of interation between a substance and an external source of energy.
Term
How does a pH analyzer work?
Definition
-Determines the concentration of hydrogen ions
-An EMF is developed across the glass barrier proportional to the difference in hydrogen ion concentration of the unknown solution to the known KCl solution.
Term
Define the values on the pH sclae.
Definition
0-7 - Acid
7 - Neutral
7-14 - Base, Alkaline or Caustic
Term
How does a conductivity analyzer operate?
Definition
-Uses two parallel platinum electrode plates immersed in a solution.
-Uses a known voltage and current from EMF to determine the resistance between electrodes. Ohm's Law
Term
What is the proper way treat analytical sensors?
Definition
-Soft cloth and tap water.
-Electrodes must remain in a solution to prevent drying out.
-DO NOT use brushes to avoid scaching electrode surfaces.
Term
Outline the sequence req'd to program a microprocessor based analytical instrument.
Definition
-Set DIP switches, program time, alarms, etc and calibrate using vendor manual and scaling document.
Term
How do you calibrate a pH analyzer?
Definition
-Standardizing
-Two known buffer solutions are used and analyzer is adjusted per scaling.
Term
How do you calibrate a conductivity analyzer?
Definition
-Replace the probe with a decade box and the temperature compensator with a resistor value specified by the vendor manual.
-Adjust as necessary.
Supporting users have an ad free experience!