ac study Flashcards
Hydraulic actuators generally operate at lower pressures than pneumatic actuators
False
In thermocouple circuits, cold junction compensation is used to eliminate errors due to the effects of
ambient temperatures
The coefficient of __________ expansion is the amount a unit volume of a material expands or contracts with temperature changes
volumetric
____________ are commonly used in industry to identify equipment that is running hotter than normal
Thermal imagers
RTD’s, thermistors and strain gauges are essentially resistors T/F
True
Feedback Control is commonly implemented using digital computers. T/F
true
Which of following input transducers would function by a change in resistance ?
- Thermistor
- RTD
- Strain Gauge
all of them
In a closed loop automated system the error signal is determined from the sensor feedback signal and the _________ signal.
Set point
What is an actuator?
A device that adjusts the process variable
Modern _________ contain instruments that can use inputs from many types of devices and combine digital and analog output signals to a controller.
control loops
The letter designation for thermocouple wires specifies a _______________.
voltage-temperature relationship
In batch production applications, ____ are the two most common process variables that must be regulated to control the rate of reaction.
temperature and pressure
A transmitter __________.
a)
converts a signal from the sensor into a standardized signal
b)
is used to boost and send signals to a remote location
Both a and b
A new steady-state condition occurs ____ time constant(s) after a controlled variable is exposed to an energy change.
5
I operate by sending sound waves toward the target & measuring the time it takes for the pulses to bounce back.
Ultrasonic Sensor
If a pressure gauge displays a reading of 50 psig, what is the absolute pressure?
about 65 psia
Which of the following devices is used for sensing the position of an object by measuring the time it takes for a transmitted pulse to be echoed back?
Ultrasonic Transducer
Some open-loop automatic control systems are self-regulating. T/F
False
A sensor is usually a transducer. T/F
True
The hydrostatic pressure created by a liquid in an open container __________ when its temperature increases.
stays the same
What is the primary function of an “actuator”?
Alter the process variable
What name is usually given to the system element that is described in the diagram below as a “Summer ”?
Comparator
The psia pressure reading of an inflated tire is the pressure __________.
above a vacuum
Feedback Control is always implemented using digital computers. T/F
False