fundamentals of instrumentation

  1. A signal then is sent to a ______________, which executes a control action.
    The final control element receives this from the primary element.
  2. is the method by which we regulate a particular process?
    process control.
  3. The field instruments that gather process data (I e., input devices) and transmit the data to the controller in the form of electrical signals, as well as the output devices?
    The I/O devices are.
  4. Typical signals used in process control are of 3 types?
    analog, discrete, and digital are the 3 types of this.
  5. analog signal usually represents a range of values read by a sensor. represented by _____volts, ____ mA, a variable pressure (______psi), or by other means.
    • 1-10 volts
    • 4-20mA
    • 3 to 15psi
  6. A marshaling panel connects field wiring to __________. Inputs and outputs are typically assigned a rack, slot, box, or point assignment to terminate field wiring.
    controller termination points are usaully located here from field wiring. PP5
  7. Another form of signal used is the discrete signal. What is a discrete signal when it comes to its function?
    A discreet signal is simply on/ off, but is always a control signal.  Versus binary, which is on and off. An example of discrete control is the application of a sump pump with high and low switches that turn a pump on or off, depending on the level in the sump
  8. The transmission of electronic signals to and from a controller is most often accomplished through the use of what to avoid induction and interference?
    Twisted-pair wiring and often shielded. Wires are twisted around each other to negate capacitive and inductive effects on the current flowing in the conductors. PP6

    • What is often redundant in controls?
    • communication lines.
  9. The process of adjusting an instrument or component on a deviation chart so that its reading can be correlated to the actual value being measured? PP7
  10. In a shared Controller, the resulting execution of the instructions entered into the controller are referred to as a?
    A scan is an execution of the instructions entered into this. PP9
  11. Process tubing is also called what?
    Impulse tubing is called this. PP9
  12. Instruments that are used in process control systems are identified by this? PP10
    An identification code or tag number identifies this. This unique code lows a device’s function to be determined by locating the tag number on a drawing or specification sheet. The tag number can provide information on how the device operates, its control purpose, and the loop designation it receives.
  13. That part of a loop or instrument that first senses the value of a process?
    The primary element is this. PP10
  14. These describe the operational intent of the control loop rather than individual instruments. PP10
    function blocks describe this.
  15. Shows all related (loop number) devices for controlling means and the wiring path, termination points, and device locations? PP13
    What is a Loop Sheet.
  16. A record of devices listed by tag number showing
    set points
    material construction
    process exposure
    and related environmental variables is?
    A spec sheet. PP13
  17. This usually only indicates termination points of controlling means?
    Elementary drawing does this. PP13
  18. Array of values over which a transmitter is intended to measure and is indicated by Engineering Units of measurement?  Versus a span, which is just an upper and lower limit range.
    what is a range. PP20
  19. correctly analyzing determines whether the necessary steps to adjust the transmitter are needed. This process, known as __________, simulates the process the instrument will measure and determines whether corrective action is needed. PP20
    Bench calibration is simulates this process.
  20. To properly perform an instrument calibration, it is necessary to understand the concepts of ________and _______of an instrument’s input and output signals. PP20
    range and span must be understood to properly perform this.
  21. Accuracy equals? PP21
    deviation/span=accuracy percent (x100).The difference between true and measured values, divided by the instrument’s span and multiplied by 100. equals accuracy in a percent.
  22. Precision is the repeatability of an instrument to record the same output signal to its corresponding input. Precision has nothing to do with? PP23
    Accuracy has nothing to do with this.
  23. To calculate the accuracy of a transmitter the level of accuracy depends on gain. Gain is the measure of? Represented by what formula? PP22
    Consistent output deviation. How much an output could change given the same input change. It is the most important factor used to determine the level of accuracy. Gain = the output/input span.
  24. How do we know when an instrument is correctly calibrated to a certain accuracy and precision? We use standards that establish guidelines for acceptable instrument calibration. For each input and output to a transmitter, what must be used? PP23
    An input test standard must be used.. For the output, an output test standard must be applied.
  25. What defines the smallest detectable increases of measurement, usually defined by the smallest reading of bits used? And what testing instrument is an example?PP24
    To define a reading of the smallest bits used, defines resolution.  A pneumatic calibrator does this.
  26. What may refer to the maximum output deviation from the mean output? And how is this expressed? PP23
    Repeatability is expressed as the maximum difference between two readings. Taking the 5 measurements, finding the averaged and then the difference between each two and then find their mean average for each set. These two numbers then give you the maximum output deviation from the mean output.
  27. ______ is how closely an instrument reflects its input, and_______ is a term given to an instrument that reflects the same output signal from a constant input signal, time after time. PP23
    Accuracy and repeatability.
  28. Calibration can adjust for several types of instrument errors. What are the most common? PP25
    • Zero shift: deviation is consistent throughout the signal span (difference between the upper and lower limit of a range expressed in the same units)
    • span error
    • nonlinearity (proximity of a calibration line to an established straight line)
    • dead band: The change through which the input to an instrument can be varied without initiating an instrument response. 
    • hysteresis: Difference between upscale and downscale results in instrument response when subjected to the same input approached from opposite directions. 
    • …are the most common of these.
  29. What is the term for an instrument whose output is consistently higher or lower than the expected value?
    Zero shift is consistent throughout output signal span, or to state it correctly, the deviation is consistent throughout the signal span.Image Upload 1
  30. ____________is performed to verify that an instrument is properly calibrated over its full output signal span. A simulated input is applied at 0%, 25%, 50%, 75% and 100% of the input range.
    A five-point check.
  31. For either instrument error, turning the zero adjustment screw can correct the problem. What are the two errors.
    Image Upload 2
    These two errors are suppressed or elevated zero shift. PP25
  32. Calibrating an instrument with span errors requires what? PP29
    five-point check, then zeroing with the adjustment screw and then correcting span with the span adjustment.
  33. What are the most common errors found in an instrument pp29
    Zero and span errors are the most common errors found in an instrument
  34. To correct _______ , the instrument must first be zeroed, and the span is then adjusted. pp29Image Upload 3
    span is corrected this way.
  35. Define Nonlinearity. PP.29Image Upload 4
    Proximity of a calibration curve to a specified, straight line, during any one calibration cycle. Nonlinearity produces an output that, when measured and plotted, does not have any consistent error shift between the upper and lower its of its range. A large linearity problem is not correctable, and the instrument must be repaired. In some cases, nonlinearity errors are small enough that their effect is scarcely noticeable, but these errors often increase with time.
  36. Recording output measurements throughout the input range causes different outputs moving up or down is defined as? What device type does this most commonly occur in. PP30
    Image Upload 5
    Hysteresis. Which is not commonly found in electronic instruments; it usually occurs in mechanical measuring devices.
  37. Define dead band. PP31
    Deadband occurs when the input value can be varied but no visible output change can be recorded. Dead band can be a very small value that is within the tolerances specified.
  38. Is Deadband adjustable? What can be done? PP31
    No. When the dead band error becomes significant enough to stray beyond the toll specified, the instrument may be in need of repair. Deadband usually isn’t adjustable, but the error magnitude may be reduced by adjusting the gain of the instrument.
  39. Name this instrument. And what does it do? PP32
    Image Upload 6
    decade box. which can be used to simulate the resistance of a load.
  40. Name this instrument. PP32
    Image Upload 7
    Wallace and Tiernan portable pneumatic calibrator also called a Wally box.
  41. What is the following instrument? And what does it do? PP32
    Image Upload 8
    Yokogawa CA12 Handy Cal, which calibrates resistance temperature detectors (RTD’s) and thermocouples.
  42. The Fluke 744 measure and source pressure using any of 29 fluke _________?
    Measure/source pressure using any of 29 Fluke 700Pxx Pressure Modules
  43. What is this a picture of and what is it used with?Image Upload 9
    700pxx pressure module used with a Fluke model 744 Documenting Process Calibrator (DPC), of which 29 current variations are available.
  44. What is the following a picture of? PP32
    Image Upload 10
    A Fluke Model 744 Documenting Process Calibrator.
  45. What is Bandwidth?
    What is a symmetrical region around the set point in which proportional control occurs.
  46. What is Baud?
    This is a unit of data transmission speed equal to the number of bits per second ( 1,200 ____ = 1,200 bits/sec).
  47. What is a pressure sensor that converts pressure to linear displacement.
    What is a bellows.
  48. The need for a pressure-sensing element that is extremely sensitive to low pressures and provides power for activating recording and indicating mechanisms prompted development of this? Most accurate in measuring? PP 37
    Metallic bellows pressure-sensing element. The metallic bellows is most accurate in measuring pressures from to 75 psi. Providing power to activate these.
  49. What is the ratio of the diameter of a pipeline constriction to the unconstricted pipe diameter.
    What is a Beta ratio.
  50. A term applied to a signal or device that has only discrete positions or states (on/off).
    What is binary.
  51. A set of things such as words, characters, digits, or parameters handled as a unit is this.
    What is a block.
  52. What is a delay in output change following a change in input.
    Lag is this.
  53. This is a straight-line flow of a fluid.
    What is Laminar.
  54. Expression of pressure in terms of the height of fluid best defines this term.
    Head pressure. PP37
  55. Diameter of the bellows ranges from? PP. 37
    0.5 to 12 inches describes the range of this.
  56. In practice, the bellows must always be opposed by _____, and the deflection characteristics reflect the resulting force of the spring and bellows.
    a spring must always oppose this. PP 38
  57. A pressure sensor that converts pressure to displacement; a coiled, flattened tube that is straightened when pressure is applied.

    What degree span is this tube usually bent to?
    What is a bourbon tube? PP38

    And is usually bent to 270 to 300 degrees in an arc.
  58. pressure detectors are used to provide up to three basic functions:
    indication, alarm, and control are the three basic functions of these? PP 38
Card Set
fundamentals of instrumentation
Fundamentals of Instrumentation; 2008, JATC