4th 2nd Q3

A thermistor is used to measure temperature in a process. The circuit includes an indicator that shows the temperature to be 88°C. Convert the Celsius temperature to its equivalent Fahrenheit value.

190.4 degrees F F= 32+ ( C x (9/5))

Ladder Diagram timer descriptions

1: timer mode 2: timer unit 3: ON=timer reset to zero; OFF=timer continues to time 4: Current timer value 5: timer preset value 6: Timer coil number

The output voltage to the motor is...

3-phase AC

The ? is controlled by voltage.

FET (field effect transistor)

Which two braking methods are most commonly used with VFDs?

DYnamic and regenerative

0-10 VDC, 4-20 ma, and 3-15 psi are examples of what type of signal?

analog

? signals provide a continuous indication of the value or position of the variable or entity being monitored.

analog

A ? has three leads, identified as drain, source, and gate.

JFET

equipment used to troubleshoot analog devices

RTD = Ohmmeter Thermistor = Ohmmeter Thermocouple = milivoltmeter Strain gauge = Milivoltmeter, Voltmeter Control vaulve = current source, pressure source

Mechanical counters have essentially been replaced by ?

electronic counters

? type latching relays have a single coil that operates a cam mechanism to change the state of the contacts each time the coil is energized (pulsed) for a minimum of 50 milliseconds.

impulse

In ? braking, a DC current is applied to two of the three windings in a three-phase motor.

injection

A ? relay is a relay that not only maintains its contacts in the last position without a continuously energized coil, but also with a mechanical mechanism or remnant magnetism until it resets electrically.

latching

? potentiometer position sensors sense the linear motion or position of some object or process that moves in a straight line. As the object moves, the shaft of the potentiometer attached to the object moves, changing the position of the potentiometer.

linear

A common type of pressure sensor used to measure weight is the ? sensor.

load cell

A ? programmed timing function does not retain its accumulated value between input signals.

non-retentive

NOTC and NCTO symbols on a control diagram represent what type of contact function?

on-delay

Analog devices connected using a voltage type analog signal are connected in ? with each other.

parallel

Loss of a phase, overvoltage, undervoltage, and out of sequence (phase rotation) are conditions that can be detected by ? sequence relays.

phase

? relays are solid-state devices that simultaneously monitor each phase of a 3-phase circuit for various failures.

phase sequence

The VFD's AC output is a ? waveform.

pulse width modulation

Programmable ? timers can emulate a seven-day time clock.

real time clock

? are analog output devices that document industrial and commercial process data .

recorders

The ? timer is a timing device in which the contacts cycle open and close repeatedly once the timer is activated.

repeat-cycle

RTDs and thermistors are temperature sensing devices that exhibit a change in ? , which is dependent upon the temperature of the device.

resistance

A ? programmed timing function retains its accumulated value between input signals.

retentive

? potentiometers position sensors detect the angular or rotational position of a shaft. As the shaft rotates, the position of the potentiometer shaft rotates as well, and the resistance output of the sensor changes to indicate that shaft's position.

rotary

Wound rotor motor speed control is accomplished by inserting resistors in series with the ? winding of the motor.

rotor

A linear variable differential transformer has three windings. The primary winding is connected to an AC voltage. The secondary windings are connected in ? , and the output from these windings represents the position of the process being monitored.

series

Analog devices connected using a current loop analog signal are connected in ? with each other.

series

When two or more thermocouples are connected in ? to increase the output voltage from the sensor, the connection is referred to as a thermopile.

series

A diode that has a low resistance at both polarities is ? .

shorted

A(n) ? converts from one analog signal range to a different analog signal range when the analog signal values do not match.

signal conditioner

What type of device has one type of analog signal as an input, and produces another type of analog signal as an output?

signal converter

Programmable timers can perform as multiple separate timers that can ? perform different timing functions.

simultaneously

? NPN transistors are used in the inverter section.

six

What type of flow meter depends upon the twist of the tube containing the flowing fluid to sense flow rate?

coriolis

When a transistor operates as a open switch, it is in the ? region.

cutoff

When the core of a linear variable differential transformer (LVDT) is in the center or null position, the voltages in the two secondary transformers are equal. Since these transformers are connected to oppose each other, the resulting output voltage is zero since the voltages cancel each other out.

true

When troubleshooting VFDs, one should narrow problems to a specific system and eliminate external problems such as power source and motor load.

true

What type of flow meter requires that particles must be present in the fluid being monitored to reflect signals back to the flow sensor?

ultrasonic

? are electronic devices that monitor an AC or DC voltage and provide an output if that voltage is out of specification.

voltage sensors

The diac acts like two ? diodes in series; therefore, it is primarily used as a triggering device for other semiconductors.

zener

What type of signal is continuous, varying from a minimum to a maximum value?

analog

Vector drives are ? expensive than other variable frequency drives.

more

When the gate pulse is removed from an SCR, the SCR will stop conducting.

false

? devices include pump sequencers or alternators and motor-driven sequence switches.

sequencing

Changes in occurrence of the input voltage to adjust the motor speed for the wound rotor motor uses what method of speed control?

frequency control

The SCR is a ?-wave device.

half

Amplification and ? are the two main operating functions of the transistor.

switching

Thermocouple transmitters generally produce 0-15 mA output signals.

False 4-20 mA

A(n) ? flow sensor uses an object called a bluff body, which is placed in the fluid flow to produce whirlpools or eddies in the fluid flow stream.

vortex

If an analog circuit with a 4-20 mA DC-current-based analog signal is reading 12 mA and a 1-5 VDC relay is connected to the circuit with a 250 ohm resistor in parallel with the input terminals, what would be the relay input voltage?

3 V DC .012 (I) x 250 (R) = 3 VDC signal

A(n) ? signal can be used to control the speed of a motor, determine the position of a valve, or indicate the level of a tank at every level as the tank fills or empties.

analog

Transducers convert a variable such as temperature, position, flow, or pressure into a(an) ? signal that is used by the control system.

analog

A ? pressure sensor often uses an LVDT to sense position relative to the pressure applied to the sensor.

bourdon tube

Standard NO and NC symbols on a controldiagram represent what type of contact function?

instantaneous

Drum brakes in an automobile are an example of ? braking.

mechanical

Thermocouples are temperature-sensing devices that produce a ? when the temperature increases.

milivolt level voltage

The control knob on many washing machines is a common example of a ? sequencing switch.

motor driven

A(n) ? is used to provide a signal between two electrically isolated circuits.

optocoupler

A(n) ? conducts current as a function of light intensity.

phototransistor

The ? is a solid-state device that combines a photodiode and a transistor.

phtototransistor

The ? value is the number of time units a programmed timer is programmed to count before timed contacts change state.

preset

? refers to a predetermined step-by-step process that accomplishes a specific task.

sequencing

Motor driven proportional control valves are generally ? to operate than pneumatic control valves.

slower

? devices need constant power to operate. The timing functions are initiated by the presence or absence of a separate "trigger" signal.

solid-state

Resistance temperature detectors (RTDs) and thermocouples are typical of analog sensing devices that measure ? in a process.

temperature

When considering response time to a change in stator temperature in a motor, thermocouples are faster than RTDs and would provide a quicker response than an RTD.

true

To test semiconductor devices, one must understand the ? of forward-biasing a PN junction and reverse-biasing a PN junction.

cause and effect

A(n) ? vector drive uses a shaft encoder on the motor shaft to give shaft rotation data back to the drive.

closed-loop

? have contacts that prevent continuous power from being applied to the coil after it has been energized.

coil clearing contacts

Transistor circuits are identified by the terminal that is ? to the input and the output.

common

A ? and ? can be a tremendous aid when troubleshooting programmable timers.

computer and the manufacturer's programming software

The transistor switches in the inverter stage are driven by the ?

control logic

In a VFD, the ? section of the VFD converts the incoming AC voltage into rectified DC voltage.

converter

Generally, ? signals with a very low source resistance are less sensitive to electrical noise from welders and electric motor starters.

current

When analog control devices are located large distances from each other, which type of signal is preferable for installing the control wiring?

current

When a transistor operates as a switch, it is in the ? region or ? region.

cutoff / saturation

? counters have a numerical readout and are programmed to count up, count down, or count up and down depending on application.

electronic

One important first step in troubleshooting programmable devices is to determine ?.

if it is a hardware or software problem

The inverter section converts the filtered ? voltage to pulse width modulated ? voltage

DC /AC

Which section of a VFD conditions the pulsating DC output voltage waveform from the previous section, filtering and smoothing the waveform, to produce a pure DC waveform?

DC bus

The coils of mechanically latching relays are rated for continuous operation.

False. the latching relay is not rated for continuous duty so continuous power to to the coils often damages the relay

? relays are used in special applications where the load usage requires equal run time between two loads.

alternating

? counters use shaft rotations to increment or decrement numerical wheels to display an accumulated count.

mechanical

When the latch coil of a(n) ? latching relay is energized, the contacts change to their activated state. At the same time, a mechanical mechanism engages and holds the contacts in this state even after the latch coil is de-energized. When the unlatch coil is energized, it trips the mechanical mechanism, allowing the contacts to return to their normal state.

mechanical

The actual amount of time a programmable timer measures is the ? value times the time base.

preset

When a transistor operates as a closed switch, it is in the ? region

saturation

To operate a wound rotor motor at full speed, the rotor windings must be ? .

shorted together

Rotor windings in wound rotor motors are connected to ? on the shaft of the motor. Brushes allow those windings to be connected to external resistors to control the speed of the motor.

slip rings

Braking of motors is used to reduce the time it takes a rotating motor to stop rotating after power is removed from the terminals.

true

? counters accumulate input pulses from two inputs and provide an output after the preset count value is reached, one input adds counts and one input subtracts counts from the accumulated total.

up/down

Phase current to a VFD motor load should vary no more than ? in each phase.

10%

Typical time bases available for programmable timers are ....

0.01, 0.1, or 1 seconds

Which type of analog signal can be used to not only control the speed of a motor, but also the direction of rotation of the motor?

+/-5 VDC

What is the temperature range that a Type J thermocouple can sense in a process?

-190°C to +800°C

A certain process control system utilizes a tank that is 10 feet tall. The transducer that measures the level of liquid in the tank is located 2 feet from the bottom of the tank. If a 1-5 VDC signal is used to monitor the top 8 feet of water in the tank, how much water is in the tank when the analog value read at the transducer is 3.5 VDC?

7 Note: A 4 volt signal (5 V - 1 V) represents 8 feet of water in the tank. 4 V/8 feet = 0.5 volts per foot. 3.5 volts represents 3.5 V - 1 V = 2.5 volts of signal. 2.5 V/0.5 V = 5 feet of water. Since the transducer is only monitoring the top 8 feet of water in the tank, the height of water in the tank is 2 feet (not monitored) + 5 feet (the measured value) = 7 feet. There are 7 feet of water in the tank.

The diac has two terminals identified as ? and ? .

A1 / A2

A single coil magnetic latching relay can be used with an ?voltage.

AC control

? recycle timers allow independent control of the ON period and OFF period.

Asymmetrical

The ? is controlled by current.

BJT

A ? has three leads identified as base, collector, and emitter.

BJT (base-emitter junction)

The gate lead controls or triggers the ? .

SCR

A(n) ? has three leads, identified as anode, cathode, and gate.

SCR ( silicon-controlled rectifier

Voltage source for the VFD

Single phase AC

Programmable timers can be programmed with the front panel keypad and LCD display, but the recommended approach is to use.......

a PC and the software supplied by the manufacturer.

Programmed timers' output contacts change state when the ? value equals the preset value.

accumulated

The ? value is the current number of time units a programmed timer has counted after the timing period has been initiated.

accumulated

When a transistor operates as a linear amplifier, it is operating in the ? region.

active

Which type of pressure sensor replaces atmospheric pressure as a reference pressure with a second process pressure?

differential pressure

A limit switch is an example of a(n) ? signal.

discrete

What type of signal has only two states: ON and OFF?

discrete

Dynamic, flux, injection, and regenerative are four types of ? braking techniques.

electrical

Proportional control valves are always controlled with an electronic voltage or current signal.

false Some proportional control valves are controlled with an analog pressure signal, generally 3-15 pounds per square inch (psi). This pressure is sometimes created, however, with a current-to-pressure converter which converts a 4-20 mA electronic signal into a 3-15 psi pressure signal.

Compared to relay contacts, transistors are .....

faster and more reliable

More precise motor speed control can be accomplished using a vector drive, which uses ? to modify the PWM output of the VFD.

feedback

In a single-phase motor speed control, the thyristor controls power in the circuit by changing the ? angle of the AC sine wave that drives the motor.

firing

Turbines and paddlewheels are often immersed directly in a process liquid and are used to measure ? .

flow

A PN junction should exhibit a ? resistance when it is forward biased, and a ? resistance when it is reverse biased.

low/ high

? latching relays have either single or dual coils.

magnetic

? latching relays use residual magnetic force to hold the contacts in position after the coil is de-energized.

magnetic

In a(n) ? latching relay with a single coil, the coil is pulsed with voltage at one polarity, and the solenoid plunger pulls in and is held in place by residual magnetism in the coil's core. When the coil is pulsed with voltage at the opposite polarity, the residual magnetism is canceled and the armature is released.

magnetic

Constant temperature and calorimetric sensors are types of ? flow sensors.

mass

? latching relays have a latch coil and an unlatch coil.

mechanical

A variable frequency drive provides a 48 hertz AC voltage to a 3-phase AC motor that has four poles per phase. What would be the synchronous speed of the motor with this voltage applied?

1440 RPM

? timers have a coil and the timing function is initiated when the coil is energized or de-energized.

Electromechanical

Iron and constantan thermocouple wire are required for ? -type thermocouples.

J

? are well-suited for switching operations.

JFET's (junction field-effect transistor)

The center material of a bipolar junction transistor is called a ? .

base

The contacts of an alternating relay change state each time the initiating circuit is ?.

opened

For a BJT to operate as an amplifier, the base-emitter junction must be ? biased and the base-collector junction must be ? biased.

forward/ reverse

A ? relay is a solid-state device that monitors a single-phase voltage and will change output contact status when a deviation from nominal frequency is detected.

frequency

The triac is a ? -wave device.

full

The converter section of the VFD uses a ? to convert the incoming AC voltage to a pulsating DC voltage.

full wave bridge

A solid-state ? timer requires constant power to operate electronics. When a signal is received from the trigger circuit, the "contacts" will instantly change state. They will remain in this state the entire time the trigger signal is present. When the trigger signal is removed, the timing period is initiated. When the timing period has elapsed, then the contacts will return to their normal state.

off-delay

Field-testing semiconductor devices focuses on using a(n) ? to determine if PN junctions in the device are functioning properly.

ohmmeter

The solid-state ? timer requires constant power to operate the electronics. When a signal is received from the trigger circuit, the timing period is initiated. When the timing period has elapsed, the "contacts" change state. The contacts will remain in the activated state the entire time the trigger signal is present. The contacts will return to their normal state as soon as the trigger signal is removed.

on-delay

The ? solid-state timer is a timing device in which the "contacts" will instantly change state when the timer is powered on or an external trigger is applied. The contacts will remain in the activated state until the timing period has elapsed.

one shot

A diode that has a high resistance at both polarities is ? .

open

Another name for a sensorless vector drive is the ? vector drive.

open-loop

Programmable logic relay timing functions provide an adjustable ? that allows precise timing with accuracy within a hundredth of a second.

time base

A ? is a device that receives one type of energy and converts it to another type of energy and generally includes a sensor and a transmitter.

transducer

A ? is used to convert the input voltage to the voltage required by the inverter section of the VFD

transformer

The ? has three leads, identified as gate, main terminal 1, and main terminal 2.

triac

Single-phase motor speed control circuits use SCR or ? to control power to the motor for speed control.

triacs

A 1-5 VDC analog device can be used in a 4-20 mA DC loop circuit if a 250 ohm resistor is connected across the input to the device and the 4-20 mA DC current is routed through the resistor. The current signal produces the proper voltage to operate the 1-5 VDC device.

true

Discrete control valves are either open or closed. Since these valves have only two states, they do not require analog input signals and operate simply by applying the appropriate voltage to the coil of the valve.

true

Electronic devices should be removed from the circuit before they are tested.

true

Proportional control valves respond to an analog signal and adjust flow over a range of 0% to 100% of the capacity of the valve. The rate of flow in these valves is proportional to the analog signal applied to the valve.

true