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Questions and Answers
Questions and Answers
What is the primary function of a Printed Circuit Board (PCB)?
What is the primary function of a Printed Circuit Board (PCB)?
- To amplify electrical signals and regulate voltage output for sensitive circuits.
- To provide structural support for large electronic components and act as a heat sink.
- To store electrical energy and filter out unwanted noise from the power supply.
- To serve as a flat insulating surface for connecting miniaturized components in a predetermined design. (correct)
What results from adapting printed circuit boards readily as plug-in units?
What results from adapting printed circuit boards readily as plug-in units?
- An increase in the complexity and size of electronic equipment due to added connectors.
- A greater need for terminal boards and complex wiring solutions.
- An increased vulnerability to vibrations and mechanical stress.
- A substantial reduction in the overall size of electronic equipment. (correct)
What problem did PCBs solve compared to the earlier method of point-to-point wiring?
What problem did PCBs solve compared to the earlier method of point-to-point wiring?
- Reduced component density by maximizing the space between individual parts.
- Increased the use of high-power leads and cabling throughout electronic devices.
- Minimizes failures at wire junctions and short circuits caused by aging insulation. (correct)
- Eliminated the need for specialized tools and soldering techniques.
What best describes the composition of a basic printed circuit board?
What best describes the composition of a basic printed circuit board?
What purpose does the substrate, or laminate, serve in a printed circuit board?
What purpose does the substrate, or laminate, serve in a printed circuit board?
What are the thin wires on the surface of a PCB that establish electrical connections referred to as?
What are the thin wires on the surface of a PCB that establish electrical connections referred to as?
What is the purpose of the solder mask on a printed circuit board?
What is the purpose of the solder mask on a printed circuit board?
What best describes Through-Hole Technology (THT) in PCB assembly?
What best describes Through-Hole Technology (THT) in PCB assembly?
What is a key disadvantage of Through-Hole Technology (THT) compared to Surface Mount Technology (SMT)?
What is a key disadvantage of Through-Hole Technology (THT) compared to Surface Mount Technology (SMT)?
In Surface Mount Technology (SMT), how are components attached to the PCB?
In Surface Mount Technology (SMT), how are components attached to the PCB?
What is achieved by using SMT components instead of THT components on a PCB?
What is achieved by using SMT components instead of THT components on a PCB?
On a PCB, what purpose do voltage and ground planes serve?
On a PCB, what purpose do voltage and ground planes serve?
What is the function of 'Edge Connectors' on a PCB?
What is the function of 'Edge Connectors' on a PCB?
Which limitation characterizes single-sided PCBs compared to double-sided or multilayer PCBs?
Which limitation characterizes single-sided PCBs compared to double-sided or multilayer PCBs?
What are 'vias' in the context of double-sided PCBs?
What are 'vias' in the context of double-sided PCBs?
What is a key characteristic of multi-layer PCBs?
What is a key characteristic of multi-layer PCBs?
What is the function of a servomechanism?
What is the function of a servomechanism?
Why are servomechanisms crucial for modern aircraft flight-control systems?
Why are servomechanisms crucial for modern aircraft flight-control systems?
What is a key feature of a servomechanism?
What is a key feature of a servomechanism?
In a basic servomechanism, which component manages the entire system?
In a basic servomechanism, which component manages the entire system?
What is a 'disturbance' in the context of a servomechanism?
What is a 'disturbance' in the context of a servomechanism?
In a closed-loop system, what is the role of 'feedback'?
In a closed-loop system, what is the role of 'feedback'?
What does 'null point' refer to in synchro or transducer terminology?
What does 'null point' refer to in synchro or transducer terminology?
What is the function of a 'summing point' in a control system?
What is the function of a 'summing point' in a control system?
What is the primary function of a transducer?
What is the primary function of a transducer?
Which of the following describes an open-loop control system?
Which of the following describes an open-loop control system?
What is a key disadvantage of open-loop control systems?
What is a key disadvantage of open-loop control systems?
What is the defining characteristic of a closed-loop control system?
What is the defining characteristic of a closed-loop control system?
How does closed-loop control differ from open-loop control?
How does closed-loop control differ from open-loop control?
What is meant by the term 'follow-up' in the context of control systems?
What is meant by the term 'follow-up' in the context of control systems?
In automatic flight control, what is the purpose of a 'follow-up' signal?
In automatic flight control, what is the purpose of a 'follow-up' signal?
What best describes an analogue transducer?
What best describes an analogue transducer?
What is a common application of analogue transducers in aircraft?
What is a common application of analogue transducers in aircraft?
How do analogue devices, such as transducers, typically represent the variables they measure?
How do analogue devices, such as transducers, typically represent the variables they measure?
What distinguishes active transducers from passive transducers?
What distinguishes active transducers from passive transducers?
On what phenomenon is the hall sensor theory based?
On what phenomenon is the hall sensor theory based?
What is the output of a Hall effect sensor when a magnetic field is applied perpendicular to the current flow?
What is the output of a Hall effect sensor when a magnetic field is applied perpendicular to the current flow?
In modern systems, what is a primary advantage of using digital transducers over analogue transducers?
In modern systems, what is a primary advantage of using digital transducers over analogue transducers?
How does an Incremental Encoder determine position?
How does an Incremental Encoder determine position?
What is the key feature of an Absolute Encoder?
What is the key feature of an Absolute Encoder?
What best describes a Linear Variable Differential Transformer (LVDT)?
What best describes a Linear Variable Differential Transformer (LVDT)?
How are the secondary windings connected in an LVDT?
How are the secondary windings connected in an LVDT?
What determines the magnitude and phase of the output voltage in an LVDT?
What determines the magnitude and phase of the output voltage in an LVDT?
In a Capacitance Transmitter, what mechanical property is measured and converted into an electrical signal?
In a Capacitance Transmitter, what mechanical property is measured and converted into an electrical signal?
How is capacitance varied in a typical capacitance transmitter?
How is capacitance varied in a typical capacitance transmitter?
How does an inductive transmitter work?
How does an inductive transmitter work?
What factor determines the portion of secondary voltage induced into the output coil of an inductive transmitter?
What factor determines the portion of secondary voltage induced into the output coil of an inductive transmitter?
What is the practical benefit of using lines of conducting material (copper, silver, gold, etc.) in PCBs, compared to traditional wiring methods?
What is the practical benefit of using lines of conducting material (copper, silver, gold, etc.) in PCBs, compared to traditional wiring methods?
Before PCBs, point-to-point wiring was common. What was a primary issue caused by this method?
Before PCBs, point-to-point wiring was common. What was a primary issue caused by this method?
What is the purpose of etching away part of the copper foil during the manufacturing process of a PCB?
What is the purpose of etching away part of the copper foil during the manufacturing process of a PCB?
What is the purpose of drilling holes in the pads or terminals of a printed circuit board?
What is the purpose of drilling holes in the pads or terminals of a printed circuit board?
Which of the following is a primary function of the silk screen (legend) on a PCB?
Which of the following is a primary function of the silk screen (legend) on a PCB?
Why are connectors for cables and other devices which must withstand mechanical stress typically through-hole technology (THT)?
Why are connectors for cables and other devices which must withstand mechanical stress typically through-hole technology (THT)?
How does Surface Mount Technology (SMT) contribute to higher component density on PCBs, compared to Through-Hole Technology (THT)?
How does Surface Mount Technology (SMT) contribute to higher component density on PCBs, compared to Through-Hole Technology (THT)?
Why is manual soldering difficult when repairing PCBs that utilize Surface Mount Technology (SMT)?
Why is manual soldering difficult when repairing PCBs that utilize Surface Mount Technology (SMT)?
What is the purpose of heat sinks on a PCB?
What is the purpose of heat sinks on a PCB?
What benefit does the use of a component socket provide on a PCB?
What benefit does the use of a component socket provide on a PCB?
What is the primary limitation of single-sided PCBs compared to double-sided or multi-layer PCBs?
What is the primary limitation of single-sided PCBs compared to double-sided or multi-layer PCBs?
What is the purpose of 'vias' in a double-sided PCB?
What is the purpose of 'vias' in a double-sided PCB?
In synchro systems, what is the function of a resolver synchro?
In synchro systems, what is the function of a resolver synchro?
What distinguishes a control synchro system from a torque synchro system?
What distinguishes a control synchro system from a torque synchro system?
In a control synchro system, what happens when the rotor of the Control Transmitter (CX) is turned, and the Control Transformer (CT) is not in correspondence?
In a control synchro system, what happens when the rotor of the Control Transmitter (CX) is turned, and the Control Transformer (CT) is not in correspondence?
Questions and Answers
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Flashcards
Flashcards
Printed Circuit Board (PCB)
Printed Circuit Board (PCB)
A flat insulating surface upon which printed wiring and miniaturised components are connected in a predetermined design and attached to a common base.
Printed Wiring
Printed Wiring
The lines of conducting material, typically copper, silver, or gold, deposited directly on the surface of an insulating circuit board.
Substrate/Laminate
Substrate/Laminate
The base material of a PCB, an insulating and non-flexible material made from phenolic paper, epoxy paper, or epoxy glass, onto which the copper cladding is bonded.
Conductor Pattern/Tracks
Conductor Pattern/Tracks
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Solder Mask
Solder Mask
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Silk Screen/Legend
Silk Screen/Legend
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Through-Hole Technology (THT)
Through-Hole Technology (THT)
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Surface-Mounted Technology (SMT)
Surface-Mounted Technology (SMT)
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Null Point
Null Point
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Summing Point
Summing Point
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Transducer
Transducer
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Open-Loop Control
Open-Loop Control
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Closed-Loop Control
Closed-Loop Control
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Follow-Up
Follow-Up
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Linear Variable Differential Transformer (LVDT)
Linear Variable Differential Transformer (LVDT)
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Hall Sensor
Hall Sensor
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Incremental Encoder
Incremental Encoder
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Absolute Encoder
Absolute Encoder
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Synchro
Synchro
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Resolver Synchro
Resolver Synchro
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Torque Synchro
Torque Synchro
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Control Synchro
Control Synchro
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Differential Transmitter (TDX)
Differential Transmitter (TDX)
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Control Transformer (CT)
Control Transformer (CT)
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Voltage and Ground Lines/Planes
Voltage and Ground Lines/Planes
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Terminals/Pads
Terminals/Pads
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Edge Connectors
Edge Connectors
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Inductance Transmitter
Inductance Transmitter
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Capacitance Transmitter
Capacitance Transmitter
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Pendulous Transmitter
Pendulous Transmitter
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Analogue Transducer
Analogue Transducer
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Printed Circuit Board (PCB) Construction
Printed Circuit Board (PCB) Construction
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Study Notes
Study Notes
Printed Circuit Boards (PCBs)
- A PCB is a flat insulating surface where printed wiring and miniaturized components connect in a design attached to a common base.
- PCBs reduce the size of electronic equipment by eliminating terminal boards, fittings, tie points, and wires, and adapting plug-in units.
- PCBs provide electrical connections and component mounting in almost every electronic device.
PCB Technology
- Before PCBs, circuits used point-to-point wiring, which often failed due to wire junction issues and insulation problems.
- PCBs keep components in place and provide electrical connections between them.
- As electronic devices become more complex, PCBs are becoming more densely populated.
Basic PCB Construction
- Printed circuit boards are made from various substances, often a flat laminated composite of non-conductive substrate materials.
- Copper circuitry is buried internally or on external surfaces.
PCB Layers
- Simple PCBs have a copper layer on one side and components on the other.
- More complex circuits have multiple layers.
- High-density applications can have fifty or more laminated layers.
- The flat composite surface supports soldered or attached components.
- Copper conductors connect the components.
Base or Substrate Material
- The base material, or substrate/laminate, includes phenolic paper, epoxy paper, and epoxy glass.
- Metal foil, or cladding, usually copper, is bonded to the substrate board.
Conductor Pattern
- The board substrate is insulating and non-flexible.
- Thin wires on the surface are part of a copper foil.
- Copper foil is etched away, leaving a network of thin wires forming the conductor pattern or tracks.
- These tracks provide electrical connections between the components.
- Holes are drilled for component leads, which are then soldered to the copper foil.
Solder Mask and Silk Screen
- The solder mask, green or brown, insulates and protects thin copper wires from corrosion.
- It prevents solder from attaching outside connection points.
- A silk screen, consisting of text and symbols, labels component locations and is also referred to as the legend.
Through-Hole Technology (THT)
- Components mounted on one side with leads soldered on the other are called through-hole PCBs or THT.
- THT components take up space and need a drilled hole for each leg.
- THT components are mechanically well-connected to the PCB.
- Connectors for cables are usually THT to withstand mechanical stress.
THT Component Mounting
- Component legs are soldered to the conductor pattern.
- Single-sided PCBs have components on one side and conductors on the other.
- Holes are needed for the component legs to penetrate the board.
- The top and bottom sides of a single-sided PCB are called 'component side' and 'solder side', respectively.
Surface-Mounted Technology (SMT)
- SMT components are soldered to the conductor pattern on the same side of the PCB.
- SMT doesn't require holes.
- SMT allows components to be mounted on both sides of the PCB.
- SMT components are smaller, enabling denser PCBs.
- SMT components are generally cheaper than THT.
- Soldering SMT components manually is difficult due to their small size.
PCB Terminology
- PCBs have distinct labeling; the foil pattern varies based on the circuit function.
- Heat sinks dissipate heat and need large areas.
- Voltage and ground lines provide power to onboard components.
- Terminals or pads are points drilled with holes for component leads.
- Conductors or runs are thin foil strips between components.
- Edge connectors connect the circuit board to a special plug.
PCB Additional Components: Component Sockets
- Sockets allow components to be removable after PCB manufacture.
- The socket is soldered to the board.
- Components can be inserted or removed from the socket without solder.
Edge Connector
- Used to connect one PCB to another.
- Consists of uncovered copper pads located along one side of the PCB
- Inserted into a matching connector (slot) on the other PCB
PCB Types: Single-Sided Boards
- Components on one side, conductor pattern on the opposite side.
- Limited wiring routing, used in primitive circuits.
Double-Sided Boards
- Conductor pattern on both sides.
- Electrical connections between sides are called vias.
- Vias are holes filled or plated with metal.
- Wires can cross, making them suitable for complex circuits.
Multi-Layer Boards
- Conductive and insulating layers are sandwiched together.
- Non-conducting dielectric layer and copper foil are patterned to form circuit connections.
Servomechanisms (4.3)
- Servomechanisms are automatic devices used alongside electronic, hydraulic, or mechanical systems and use error-sensing negative feedback to correct action and maintain desired conditions.
- In aircraft, digital signals transmit pilot instructions to servomechanisms, positioning control surfaces as needed. Modern systems use accelerometers for stability.
- Flight-control systems rely on servomechanism technology.
Servomechanism Terminology
- A servomechanism (servo) uses an external power source to move a load with forces greater than the input level and is a control system type.
- Servomechanisms measure and control in aircraft systems like pressurization, brakes, flight/engine control.
- Applies to systems using feedback/error-correction to control mechanical position, speed, attitude, or other variables.
- A car's power window control is a servomechanism, while cruise control uses closed-loop feedback.
- It provides a command device, amplification, work instrumentation, and feedback provision.
Two Main Classes of Servomechanism
- Position control.
- Speed control.
Basic Servomechanism Components
- Controller: Manages the system; may be a computer processor.
- Disturbance: Forces output change without input change; turbulent winds.
- Feedback: Mechanical, electrical or aerodynamic used in autopilots.
- Closed-loop systems employ feedback.
Null Point
- Point in a field where the field quantity is zero.
- Point where output voltages are neither positive nor negative.
- In synchro systems, where the output position matches the desired input position.
Summing Point
- Part of a system where error signals are modified.
- In modern systems, summing is a software function.
Transducers
- Devices that convert one form of energy into another.
Transducer Types
- Temperature transducers convert temperature changes into electrical voltages or mechanical movement.
- Electric motors convert electrical energy into kinetic energy.
- Pressure transducers change barometric pressure into electrical voltage.
Transducer Notes
- Moduled transducers only convert to electrical signals.
- Transducers that produces other energy outputs are called actuators.
Open-Loop Control
- Control action is independent of the output.
- Open-loop control does not self-correct deviations from the required value.
- Open-loop control can be manual or connected to a timer.
- Its simpler and less expensive than closed-loop control.
- Errors are not automatically corrected.
- A simple motor rotating a television antenna is an open-loop servomechanism.
Control Systems and Feedback
- A control system manages, commands, directs or regulates other devices/systems using control loops.
- A servomechanism utilizes an electronic control system; for continuous control a feedback loop is implemented .
- Closed-loop control adds feedback, measuring the difference between actual and demanded results.
- This system drives the actual result towards the desired one yielding accurate control.
Follow-Up
- Cancels the control that destabilized the system to create a controlled change.
- In aircraft, after initiating a turn, the ailerons must be centred to stop the rolling motion; aircraft remains in a banked condition.
- In automatic flight control, 'follow-up' is an error feedback signal generated by error detection circuits and returns the aircraft to stable flight/altitude.
- An automatic flight control system moves a control surface to adjust pitch/roll and then uses a follow-up signal to readjust the control surface.
- Approaching the selected altitude/heading, the follow-up signal is larger than the error signal, driving controls to a neutral position.
- When both signals are zero, the aircraft is on the new heading/altitude.
Analogue Transducers
- Analog transducers are often used in place of a potentiometer to relay information regarding the rate/position of a controlled device.
- In aircraft, these transducers convert the movement of physical flight controls into a variable electrical output signal to be read by the controller.
- Closed-loop control systems measure the system's variable: position, displacement, force, fluid level, pressure, flow rate, temperature and velocity.
- Electrical transducers: Translate physical variables into an equivalent electrical variable.
- Most transducers are passive requiring external excitation for operation.
- Active transducers develop output without external excitation, examples of active transducers are the thermocouple and tachogenerator.
- Strain Gauge: Transducer that converts applied force, pressure, weight or tension into electrical signals.
Hall Sensors
- Hall sensor theory states that when applying a magnetic field perpendicular to the current to the object, the electromotive force appears in the direction perpendicular to both the current and the magnetic field
- With a semiconductor plate with no magnetic field, the current is spread out across the entire plate
- When a magnetic field is present, the current flow is pushed to one side of the plate leading to a voltage being outputted corresponding to the magnetic flux density and its direction.
Digital Transducers
- Modern systems use more digital transducers with two basic sensing systems in general use.
Incremental Encoder
- The incremental encoder outputs square wave pulses from one end of movement to the other.
- Numerical position is found by then adding or subtracting the amount of pulses moved.
Absolute Encoder
- Requires many light sources and sensors (one for each digit required)..
- An absolute encoder gives the exact position as a binary output with accuracy dependent on the number of bits.
Synchro Systems I: Linear Variable Differential Transformer (LVDT)
- LVDTs translate straight line motion into a linear AC signal proportional to the amount of movement..
- They feature one primary and two secondary windings connected in opposition, and a magnetic core (armature) positioned by a linear motion.
- In the central position, the secondary windings have equal voltage induced in coils.
- The LVDT principle of measurement is based on magnetic transfer.
- The advantage of the LVDT transducers over other types of displacement transducers is their robustness and are also waterproof.
- An LVDT comprises a coil former or bobbin onto which three coils are wound.
Capacitance Transmitters
- A capacitive sensor connected to a bridge/oscillator circuit, where plate movement varies capacitive reactance and the resultant change is converted into a measure of mechanical capacitor plate position.
- Capacitance transmitters have a rotor and stator of intermeshing plates whose relative position determines capacitance value.
Inductance Transmitters
- A mutual inductance transmitter with two coils, one supplied with alternating current, surrounded by a secondary output coil with two areas of different permeability.
- The portion of the secondary voltage induced into the output coil is determined by the level of permeability of the metal next to the coils
- Common transmitters are made of aluminum and a ferrite material and the null position is when the inductive coil is positioned on the join between the ferrite and the aluminum vanes giving half the maximum output.
Pendulous Transmitters
- Detect shifts from vertical/horizontal with primary (input) and secondary (output) winding.
- The core is secured vertically to the aircraft structure as its level, the core and frame will be in a central position on left-hand diagram.
- There is no EMF induced In the lefft hand diagram with the core centered in the frame, the flux of the primary winding does not intersect with the secondary.
- When the frame is displaced there is a low reluctance path for primary flux to intersect the secondary winding.
Synchro Principles
- Synchros are electromagnetic devices, transmitting rotational position data as low current using 3/4 wires and an AC input signal in autopilot/radar systems.
- Contains both primary and secondary windings, comparable to that of a motor.
One Synchro Type: Resolver Synchro
- Converts alternating voltages representing cartesian coordinates of a point into polar coordinates.
- A Resolver Synchro contains two windings each with their axes perpendicular to each other
Synchro Systems II
- There are two general categories of synchro systems: torque synchro and control synchro
- Torque synchros use current in rotors to generate torque to move the load, torque synchros contain components called torque transmitters, torque receivers, and torque differentials.
- Control synchros are voltage control devices using small currents, components are called control transmitters, control differentials and control transformers.
Synchros: Purpose
- Synchro system in position sensing and data transmission is very common in aircraft automatic pilot systems providing fast/accurate transmissions.
- The primary synchro is essentially a rotary transformer providing only 0.5% accuracy for torque synchro system.
Torque Synchro System
- Torque Synchro System converts mechanical movement in to electrical signals sent to another location using two items: a torque transmitter (TX) and torque receiver (TR)
- TR contains some form of damping to prevent oscillations of the rotor.
- S=Stator and R = Rotor
Torque System Accuracy
- Torque is derived from the current in the stators, and current is almost zero when aligned.
- Torque synchro systems can only drive light loads with an accuracy requirement of 0.5% of ±1.8°.
Differential Transmitter
- A torque differential synchro can be used to transmit the sum or difference of an electrical signal and mechanical signal.
- This means that they can be either a transmitter (TDX) or receiver (TDR).
- Principle of operation is the same as the torque transmitter just the rotor is designed with three separate windings which are placed electrically 120° apart.
Differential Synchros
- A differential synchro system is a three-component synchro system consisting of transmission from one transmitter synchro to a differential synchro to the receiver
- The rotor leads of the differential synchro are connected to the stator leads of the torque receiver
Differential Subtraction
- Using the differential synchro as a transmitter allows the system to add or subtract information to or from the remote torque receiver.
- The signal transmitted to the remote station being the difference between the electrical and mechanical signals.
Differential Addition
- Changed the input and output leads of the TDX.
- The shaft of the TR will revolve to a position whose angle will be equal to the angles traveled by the shafts of the TX and TDX.
Control Synchro Systems
- Torque synchro systems produce a relatively small mechanical output only suitable for very light loads.
- Control Synchro Systems provide high accuracy and high torque system by using a Control Transmitter (CX), a Control Transformer (CT), and Control Differential Transmitter (CDX) .
- The CX, CDX and CT used in indicator systems are the same units used to position large systems.
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