All Flashcards
Triacs, Diacs, ujt’s, and scr’s operate only as
Switches
When transistors are used as switches, a ____ can be mounted across the transistor to prevent damage from high voltage spikes
Diode
The ___ region is the point at which the transistor is turned off and no current flows
Cutoff
A ____ serves as the control point for an SCR
Gate
A gate current is used to reduce the level of ____ voltage necessary for an SCR to conduct or fire
Breakover
_____ Control is the control of the time relationship between two events when dealing with voltage and current
Phase
____ Is one of the most suitable industrial applications of SCR’S
DC Motor control
A ____ is needed to properly test a SCR under operating conditions
Oscilloscope
Triacs are the equivalent of two SCR‘s connected in a ____ arrangement with gates, also connected to each other
Reverse-parallel
Triacs cannot replace SCR’s in ____ applications
High-current
And important feature of Triacs is the absence of a ____ condition of high voltages and high current, such as those found in diodes, and SCR’s
Reverse-breakdown
Electronically, a Diac operates in a manner similar to two ____ that are connected in series in opposite directions
Zener diodes
A diac has ____ resistance because it does not conduct current until the voltage crossed it reaches its break over voltage
Negative
Diacs are used almost exclusively as ___ devices
Triggering
The N-type material in a Uni Junction transistor functions as the ____ and has two leads
Base
As long as the emitter voltage remains less than the internal voltage, the emitter junction will remain ___ even at a very high voltage
Reverse biased
A UJT is typically used as a triggering circuit for a _____ or similar device
Triac
The “Pin” in pin photodiode stands for p-type material, ____, and n-type material
Insulator
In a two lead phototransistor, the ____ is replaced by a clear covering that allows light to fall on the base region
Base lead
In darkness, a phototriac is not triggered, the remaining leakage current is referred to as _____ current
Peak blocking
As electrons move across the _____ of a light emitting diode (LED) they give up extra kinetic energy, which is converted to light
Depletion region
In Optocoupler, uses a ____ glass sandwich to separate input from output
Dielectric
_____ current is the amount of current drawn by load when energized
Load
Photoelectric sensors that switch DC circuits normally use ____ as the switching element
Transistors
____ current flow is the movement of electrons from positive to negative
Conventional
Communication is the transmission of information from one point to another by means of _____ waves
Electromagnetic
A fiber optic receiver, normally contains a ____ that converts light back into electrical signal
Photodiode
The ____ is the first layer of protection for the glass or plastic core of an optical fiber cable
Cladding
_____ scan is a method of scanning in which the transmitter and receiver are housed in the same enclosure, and the transmitted light beam is reflected back to the receiver from a reflector
Retro reflective
____ scan distinguishes between shiny and non-shiny (matte) surfaces
Specular
In a ____ light source, the light source is turned on and off at a very high frequency, normally several (kHz)
Modulated
For optimum performance, the photoelectric sensor should be operated when its LED is _____
Green
A ____-operated photoelectric control is a photoelectric control that energizes the output switch with a target is present (breaking the beam)
Dark
The best scanning method for height and distance monitoring is _____ scan with modulated controls
Direct
The ____ light beam is the area of light that travels directly from the transmitter to the receiver
Effective
An SSR circuit consist of an input circuit, a ____ circuit and an open circuit
Control
The input circuit is deactivated when a voltage less then the specified minimum ____ voltage of the relay is applied
Dropout
The ___ switching relay is the most widely used relay
Zero
A____ switching relay has a built-in synchronizing circuit that controls the amount of output voltage as a function of the input voltage
Analog
____ is the largest problem in applications that use an SSR
Temperature
One of the significant advantages of an SSR over an EMR is it’s ____
Response time
Even at full conduction, an SSR presents some residual resistance, which can create a voltage drop of up to approximately _____ in the load circuit
1.5v
The ____ method is a method of SSR replacement in which a logical sequence is used to determine the reason for a failure
Circuit analysis
_____ is a phenomenon that occurs when a relay fails to turn off because the current and voltage in the circuit reach zero at different times
Half-waving
An RC circuit is a circuit in which resistance in capacitance, are used to help ____ the power in a circuit
Filter
A solid state motor starter is in electronically operated switch (contactor) that uses solid-state components to eliminate mechanical contacts and includes ____
Overload protection
___ trip is the trip point after the overloads have tripped and have been reset (motor, operating near or over nameplate rated current)
Hot
A typical solid-state ____ circuit consist of both start, and run contactors connected in the circuit
Starting
___ Start is the most common solid-state starting method
Soft
___ stop is the most common solid-state motor starter Stopping method
Soft
The instillation cost for ____ motor starters tend to be the highest
Solid state
The ____ starting method provides the highest possible, starting to work per ampere of line current, and is the most effective means of motors, starting for applications, where the inrush current must be reduced with a minimum sacrifice of starting to torque
Auto transformer
A thermistor is a ___-sensitive resistor
Temperature
The operation of a thermistor is based on the ____-hole theory
Electron
____ heated thermistors are used for precision, temperature measurement, and temperature compensation
Indirectly
Cold resistance is measured at ____°c
25
A photoconductive cell (photocell) is a device that conducts current when energized by _____
Light
A photocell is in effect a variable
Resistor
_____ and contamination are the primary causes of photocell failure
Humidity
The primary difference between a photodiode and a regular diode, is that a photo diode has an addition of a _____ and it’s housing for focusing light on the PN junction
Lens
Without light, the ____ of the photo diode is high
Resistance
The ____ flowing through a photodiode, increases as the resistance decreases
Current
A voltage output, pressure sensor typically outputs 0 VDC to ____ VDC proportional to the rating of the pressure sensor
10
A current output pressure sensor typically outputs 4 mA to ____ mA proportional to the rating of the pressure sensor
20
Pressure sensors are suited for a wide variety of pressure measurements on _____, pumps, and other similar equipment
Compressors
A flow detection sensor is a sensor that detects the movement of a liquid or gas using a
Solid-state device
A flow detection sensor operates on the principle of ____ conductivity
Thermal
Because there is a small delay (usually less than 30 seconds) before a flow detection sensor, heats enough to signal no flow, the sensor acts like a ____ which allows for a short time delay to pass before signaling a problem
Motor overload protection
A ____ sensor detect the proximity of a magnetic field
Hall effect
Hall voltage varies, depending on how close the magnet is to the hall generator which acts as a ____ signal
Analog
Typical hall effect sensor package configurations include cylinder, proximity vane, and ___
Plunger
____ actuation is an active method of hall affect sensor activation, in which a magnet is oriented, perpendicular to the surface of the sensor and is usually centered over the point of maximum sensitivity
Head on
Hall effect sensors are also used to replace mechanical ____ switches in applications that require the detection of an objects position
Limit
A proximity sensor is a solid-state sensor that detects the presence of an object by means of a ____ sensing field
Electronic
An ___ proximity sensor is a sensor that detects only conductive substances
Inductive
Inductive proximity sensors operate on the ____ principle
Ecko
____ sensors came to take material such as plastic glass water moist wood, etc.
Capacitive
Generally any material with a _____ constant greater than 1.2 may be detected.
Dielectric
The high frequency sound waves of an ultrasonic sensor, or typically in the ____ KHz range
200
Material such as foam, fabric, and ____ are difficult for ultrasonic sensors to detect and are better detected by photoelectric or proximity sensors
Rubber
___ mode is a method of ultrasonic sensor operation, in which the emitter and receiver are placed opposite of each other, so that the sound waves from the emitter are received directly by the receiver
Direct
