Modules 4 & 5 Flashcards
Components in a feedback loop usually have some form of signal communication
because:
a. The controller may be a stand-alone device in a digital system.
b. Wireless communication cannot replace electrical signal transmission.
c. The components may be physically separated.
d. A backup to a manual system must employ shared digital signals.
c. The components may be physically separated.
Which of the following statements is TRUE regarding controller tuning from
closed loop tests?
a. The magnitude of the oscillation required can be easily predicted.
b. Moderate disturbances during the testing can be tolerated.
c. Multiple tests are usually not required, minimizing interruption to normal
operations.
d. The technique is based on the assumption that a first order plus dead time
(FOPDT) process model approximates the real process.
b. Moderate disturbances during the testing can be tolerated.
Which of the following are valid forms of PID algorithm?
a. Proportional and derivative modes on error, integral on measurement
b. Proportional and integral modes on measurement, derivative on error
c. Proportional, integral, and derivative modes on measurement
d. Proportional, integral, and derivative modes on error
d. Proportional, integral, and derivative modes on error
Which of the following valve actuators has the lowest cost and low friction and
deadband?
a. Electric
b. Solenoid
c. Pneumatic
d. Hydraulic
c. Pneumatic
Which of the following would be able to indicate both direction and velocity?
a. +/– 10 V
b. 4 – 20 mA
c. 10 – 50 mA
d. 3 – 15 psi
a. +/– 10 V
Which control measurement is generally expressed as the ratio of the error to the
full-scale output?
a. Response
b. Accuracy
c. Linearity
d. Repeatability
b. Accuracy
A piping and instrument diagram does NOT include which of the following?
a. Communication between instrumentation devices
b. Accessibility of devices to the operator
c. Failure thresholds
d. Instrumentation devices
c. Failure thresholds
Which of the following is TRUE of the relay method of tuning?
a. The relay method is not appropriate for automated testing.
b. The process is tested by a forced disturbance using an on-off controller.
c. The controlled variable will stay at the setpoint, with the controller output at the
minimum value.
b. The process is tested by a forced disturbance using an on-off controller.
The purpose of the plug within the control valve is to
a. send a signal to the control valve to maintain the setpoint.
b. create a flow area that modifies the flow rate.
c. measure the upstream pressure of the property.
d. allow the valve to rotate without any linear motion.
b. create a flow area that modifies the flow rate.
A pneumatic positioner is used to
a. increase fast venting capability.
b. overcome packing friction.
c. eliminate use of piston actuators.
d. diagnose itself and the valve actuator system.
b. overcome packing friction.
Which of the following is true of electric signaling?
a. The ISA SP50 committee developed a 3 mA to 15 mA signal standard.
b. The ISA SP50 committee used a three-wire loop consisting of one ground, one
current, and one signal wire.
c. Electric signaling still required an external air supply to actuate the final control
element.
d. Electric signaling overcame the dead time drawback of pneumatic signaling.
d. Electric signaling overcame the dead time drawback of pneumatic signaling.
Which of the following is characteristic of controlled processes?
a. Process measurements usually provide positive feedback.
b. Processes will exhibit zero error.
c. Controlled processes with identical equipment will respond identically.
d. A change in one controller may affect a number of process variables.
d. A change in one controller may affect a number of process variables.
Trial-and-error tuning is BEST accomplished by
a. minimizing the effects of the decay ratio.
b. using an open loop test to define tuning parameters.
c. adjusting the relationship between the integral time and the period of
oscillation.
d. examining the as-found data set related to the process.
c. adjusting the relationship between the integral time and the period of
oscillation.
What is the difference between a linear valve and a rotary valve?
a. A linear valve is suited to low pressure applications; a rotary valve can handle
high pressure applications.
b. A linear valve has a low recovery; a rotary valve has a high recovery.
c. A linear valve has an integral bonnet; a rotary valve has a separable bonnet.
d. A linear valve is flangeless; a rotary valve is usually threaded.
b. A linear valve has a low recovery; a rotary valve has a high recovery.
When using a two-wire electric signal loop to carry both the current and the signal,
which of the following is true?
a. Ohm’s Law states that as voltage is raised across a device, the current is
proportionally increased and the change in current is used as the signal.
b. A solid state device such as a bipolar triode transistor is required to keep
variance in voltage from affecting current (within reason).
c. A solid state device such as a bipolar triode transistor will determine the
collector current and not the emitter-base current (within reason).
d. Ohm’s Law states that as voltage is raised across a device, the current
remains constant and current can therefore be used to carry the signal.
b. A solid state device such as a bipolar triode transistor is required to keep
variance in voltage from affecting current (within reason).
In the ideal PID algorithm, the derivative mode may be used to
a. control the feedback device.
b. control the reset rate.
c. provide most of the correction.
d. improve response of the control loop.
d. improve response of the control loop.
The simplest technique for addressing the nonlinearity problem is
a. trial-and-error tuning.
b. scheduled tuning.
c. closed loop tuning.
d. self-tuning.
b. scheduled tuning.
What is the MOST important thing to know in troubleshooting a valve problem?
a. Temperatures the valve is exposed to
b. Fail-safe mode of the valve
c. Velocity of the valve
d. Composition of the valve
b. Fail-safe mode of the valve