Thermocouples 101
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Questions and Answers

Which type of RTD is used when very high accuracy is needed?

  • Coil element
  • Thin film sensing element
  • Wire wound element
  • 4-wire configuration (correct)
  • What is the advantage of using a 3-wire RTD over a 2-wire RTD?

  • Higher accuracy (correct)
  • Longer distance capability
  • More rugged
  • Lower cost
  • What type of temperature device exhibits a positive change in resistance for a positive change in temperature?

  • RTD (correct)
  • PTC thermistor
  • NTC thermistor
  • Thermistor
  • Which standard instrumentation signal is most commonly used for temperature measurement?

    <p>Current - 4 to 20mA</p> Signup and view all the answers

    Which type of process measurement detects the process variable within a range of all possible values at all times?

    <p>Continuous Measurement</p> Signup and view all the answers

    Which type of measurement device is in direct contact with the process and may change the process or be a source of contamination?

    <p>Direct or Invasive Measurement</p> Signup and view all the answers

    Which term refers to the difference between the desired setting of the process variable and the current measured condition of the process?

    <p>Error</p> Signup and view all the answers

    What is the lowest value that corresponds to the bottom or lowest limit of the process called?

    <p>Zero</p> Signup and view all the answers

    Which two colors are used to identify the 'J' type thermocouple?

    <p>White and red</p> Signup and view all the answers

    What is the purpose of the HART protocol?

    <p>To enable bidirectional communication between smart devices and control/monitoring devices</p> Signup and view all the answers

    What is the process variable represented by 'URV' in the HART protocol?

    <p>Upper Range Value</p> Signup and view all the answers

    Why does HART communication require a minimum loop resistance?

    <p>To enable FSK HART signal detection</p> Signup and view all the answers

    According to the text, what is the formula to convert the nonstandard signal input (°C) into a percent?

    <p>$% = PV - LRV \times 100$</p> Signup and view all the answers

    According to the text, what is the formula to calculate the output into the standard signal (mA)?

    <p>$Output = (Input - LRV) \times Span + LRV$</p> Signup and view all the answers

    Based on the given information, what should the psi output signal be if the input range is 4-20mA and the PV is 13.6 mA?

    <p>10.2 psi</p> Signup and view all the answers

    According to the text, what is the simplified formula for cold junction compensation?

    <p>$V_{true} = V_{meas} + V_{ref}$</p> Signup and view all the answers

    Which organization is responsible for standardizing P&ID symbols?

    <p>ISA</p> Signup and view all the answers

    What is the span of a thermometer with a scale from -40°C to 100°C?

    <p>140°C</p> Signup and view all the answers

    What is the purpose of a transmitter in process control?

    <p>To convert non-standard signals to standard instrumentation signals</p> Signup and view all the answers

    What is the most common material used for resistive temperature detectors (RTDs) in industry?

    <p>Platinum</p> Signup and view all the answers

    Which type of level measurement involves detecting the level of solids as well as liquids?

    <p>Solid level measurement</p> Signup and view all the answers

    Why are regular performance verifications necessary for process instrumentation?

    <p>All of the above</p> Signup and view all the answers

    Which quality program dictates periodic calibration to recognized standards for all instruments that impact product quality?

    <p>ISO 9000</p> Signup and view all the answers

    What are some factors that can cause the performance of instruments to change over time?

    <p>All of the above</p> Signup and view all the answers

    What are some problems that regular performance checks can uncover?

    <p>All of the above</p> Signup and view all the answers

    What is level measurement?

    <p>The act of detecting the interface or boundary between materials</p> Signup and view all the answers

    According to the text, what are the basic electrical equations used in instrumentation?

    <p>$E=I \times R$ and $P=E \times I$</p> Signup and view all the answers

    What is the order of operations for solving equations?

    <p>Solve brackets first, then solve exponents, perform multiplication and division from left to right, perform addition and subtraction from left to right</p> Signup and view all the answers

    What is the formula to calculate the percentage of a process variable?

    <p>$% = \frac{PV - LRV}{Pspan} \times 100$</p> Signup and view all the answers

    What is the formula to convert a percentage to a standard signal?

    <p>$mA = \frac{%}{100} \times Pspan + LRV$</p> Signup and view all the answers

    Point Measurement detects the process variable at a predetermined ______ or value

    <p>point</p> Signup and view all the answers

    Continuous Measurement detects the process variable within a ______ of all possible values at all times

    <p>range</p> Signup and view all the answers

    Direct or Invasive Measurement: The measurement device will be in direct ______ with the process

    <p>contact</p> Signup and view all the answers

    Indirect or Non-Invasive Measurement: No ______, good for extreme processes

    <p>contact</p> Signup and view all the answers

    _______ are parts of the process control that perform the function of measuring and changing the process.

    <p>Devices</p> Signup and view all the answers

    Devices that measure the process are called _______.

    <p>sensors or elements</p> Signup and view all the answers

    Instrumentation devices that convert non-standard signals to standard instrumentation signals are called _______.

    <p>transmitters</p> Signup and view all the answers

    According to the text, what is the formula to convert the nonstandard signal input (°C) into a percent?

    <p>$% = \dfrac{PV - LRV},{Ps_{pan}} \times 100$</p> Signup and view all the answers

    Devices that create changes in a process are called _______.

    <p>actuators</p> Signup and view all the answers

    What is the lowest value that corresponds to the bottom or lowest limit of the process called?

    <p>LRV</p> Signup and view all the answers

    What is level measurement?

    <p>The process of determining the height of a substance in a container or vessel</p> Signup and view all the answers

    Why are regular performance verifications necessary for process instrumentation?

    <p>To ensure accuracy and reliability of measurements over time</p> Signup and view all the answers

    An RTD is a temperature device/sensor that will exhibit a positive change in ______ for a positive change in temperature.

    <p>resistance</p> Signup and view all the answers

    The 2-wire RTD is only used for short distances and where high accuracy isn’t necessary because you are adding the resistance in the leads to the resistance of the ______.

    <p>sensor</p> Signup and view all the answers

    The 3-wire RTD is the most common because you can subtract the ______.

    <p>lead resistance</p> Signup and view all the answers

    The 4-wire RTD is used when very high accuracy is needed. With the 4-wire configuration, the instrument will pass a constant current (I) through the outer leads. The addition of the two additional leads makes it possible to eliminate errors due to change in ______ resistance.

    <p>lead wire</p> Signup and view all the answers

    According to the text, the HART protocol provides data between intelligent field instruments and DCS/PLC or handheld communicators through ________ communication.

    <p>bidirectional</p> Signup and view all the answers

    The HART protocol makes use of Bells 202 Frequency Shift Keying (FSK) standard to superimpose digital information on the conventional 4-20 mA ________.

    <p>analog signal</p> Signup and view all the answers

    The microprocessor-based field devices that offer better accuracy, long-term stability, and reliability than conventional analog instruments are known as ________ instruments.

    <p>smart</p> Signup and view all the answers

    The HART protocol uses analog and digital ________ simultaneously for communication.

    <p>communication</p> Signup and view all the answers

    According to the text, what is the formula to convert the nonstandard signal input (°C) into a percent?

    <p>$%=\dfrac{PV - LRV},{Span} \times 100$</p> Signup and view all the answers

    Based on the given information, what should the psi output signal be if the input range is 4-20mA and the PV is 13.6 mA?

    <p>$\text{Output} = \left(\dfrac{Input - LRV_{\text{input}}},{Span_{\text{input}}} \right) \times Span_{\text{output}} + LRV_{\text{output}}$</p> Signup and view all the answers

    According to the text, what is the simplified formula for cold junction compensation?

    <p>$V_{\text{true}} = V_{\text{meas}} + V_{\text{ref}}$</p> Signup and view all the answers

    What is the purpose of the HART protocol?

    <p>to enable communication between smart field devices and control systems</p> Signup and view all the answers

    Regular performance verifications with a suitable reference standard, are necessary because regulations governing occupational safety, environmental protection, and consumer safety often require evidence of traceable calibration for process instrumentation. Quality programs, such as ISO 9000, dictate periodic calibration to recognized standards for all instruments that impact product quality. Calibration is still required The performance of instruments will changeover time with exposure of the transmitter and the primary sensing element to temperature, humidity, environmental pollutants and vibration. Regular performance checks can uncover problems not directly caused by the equipment such as plugged impulse lines, or pressure lines that have become filled with condensate. Or the wrong ______ type installed.

    <p>thermocouple</p> Signup and view all the answers

    Level detection of solids can be more difficult than with liquids because solids will not take the shape of the vessel and can bridge the detection points (Primary Elements). In defining level measurement, we can say that : Level measurement is the act of detecting the interface or ______ between.

    <p>boundary</p> Signup and view all the answers

    Level measurement is divided into two familiar types of detections. ______ and Continuous level measurement.

    <p>Point</p> Signup and view all the answers

    Regular performance verifications with a suitable reference standard, are necessary because regulations governing occupational safety, environmental protection, and consumer safety often require evidence of traceable calibration for process instrumentation. Quality programs, such as ISO 9000, dictate periodic calibration to recognized standards for all instruments that impact product quality. Calibration is still required The performance of instruments will changeover time with exposure of the transmitter and the primary sensing element to temperature, humidity, environmental pollutants and vibration. ______ performance checks can uncover problems not directly caused by the equipment such as plugged impulse lines, or pressure lines that have become filled with condensate. Or the wrong thermocouple type installed.

    <p>Regular</p> Signup and view all the answers

    Level measurement can involve detecting the level of solids as well as ______‘s.

    <p>liquid</p> Signup and view all the answers

    Introduction to Level Measurement Level is simply the height that some material fills a container. Level measurement is an integral part of process control systems for inventory control, quality and safety. Level measurement is divided into two familiar types of detections. Point and Continuous level measurement. Level measurement can involve detecting the level of solids as well as ______‘s. Level detection of solids can be more difficult than with liquids because solids will not take the shape of the vessel and can bridge the detection points (Primary Elements). In defining level measurement, we can say that : Level measurement is the act of detecting the interface or boundary ______.

    <p>liquid</p> Signup and view all the answers

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