questions Flashcards
What device is similar to an RTD but has a negative temperature coefficient?
themistor
The silicon-controlled rectifier can be turned off
by forced commutation
The output voltage of a typical thermocouple is
less than 100mV
The connections to a thermocouple
can produce an unwanted thermocouple effect, which must be compensated for
What is the zero-voltage switch used for?
to reduce radiation of high frequencies during turn on of a high current to a load
Temperature sensing can be achieved by the use of
A. thermocouples
B. RTDs
C. thermistors
D. All of the above
(D)
The purpose of compensation for a thermocouple is
to cancel unwanted voltage output of a thermocouple
The change in value of an analog signal during the conversion process produces what is called the
quantization error
Which of the following performance specifications applies to a sample-and-hold circuit?
Aperture time
RTDs are typically connected with other fixed resistors
in bridge configuration
Holding current for an SCR is best described as
the amount of current required to maintain conduction
What is the moving part of a linear variable differential transformer
core
A resistance temperature detector produces a voltage for a given change in temperature.
FALSE
(RTD is a passive device it cannot produce a “VOLTAGE DROP” on its own, but it produces a change in resistance. The resistance is measured by external electronic devices by passing a small current through the RTD which would generate a voltage.)
The triac provides better dc power control than the SCR.
FALSE
The SCR is ideal for ac applications.
FALSE
Displacement, velocity, and acceleration can all be measured by using specific motion transducers.
TRUE
A strain gauge uses the principle of capacitance for its operation.
FALSE
Thermocouple connections must be taken into account to ensure a high degree of accuracy.
TRUE
Thermocouple connections must be taken into account to ensure a high degree of accuracy.
TRUE
The change in value of the analog signal during the sampling process produces what is called the quantization error.
True
Pressure transducers are devices that exhibit a change in resistance inversely proportional to a change in pressure.
FALSE
(A pressure transducer produces an electrical output proportional to the pressure applied. Are directly proportional to pressure over a wide range of frequencies.)
A basic sample-and-hold circuit consists of an analog switch, a capacitor, and an instrumentation amplifier.
FALSE
A basic sample-and-hold circuit has two operational amplifiers, an analog switch and a capacitor.
Noncontacting displacement transducers include optical and capacitive transducers.
TRUE
All triacs operate in __________.
Quadrant 1 and 3
The number of bits in a digital word determines the number of digital combinations that will be represented. The number of combinations can be calculated by ________.
raising 2 to the number of bits in the digital word
A(n) _____ can be rapidly switched on and off remotely by another controlling circuit.
triac
A sample-and-hold circuit consists of _________.
two op-amps, an analog switch, and a capacitor
RTDs, strain gauges, and pressure transducers are _____ devices.
resistive
A thermistor’s temperature characteristic is essentially _________.
logarithmic
The three types of relative pressure measurement are ________.
absolute, gauge, and differential
The two most common types of analog-to-digital converters discussed in this chapter were the ______.
flash converter and the successive approximation converter
The voltage produced by a thermocouple is called the _________.
seebeck voltage
The ________ are two types of acceleration transducers.
LVDT and the piezoelectric
A triac is different from an SCR because ________
it allows current flow in both directions
The ______ is composed of a transformer with a movable core, a primary, and two secondaries.
LVDT
