Thermal Sensors Lab

Thermal Sensors Lab

1. Thermal Sensors Lab
   1. In a processing plant, a chemical tower has a liquid which is vaporized. However, if the vapor in the tower reaches 150°C, an alarm needs to be generated so that safe shutdown of that system of the plant may be initiated. An RTD will be used to measure the temperature of the vapor. The RTD will generally operate between 80° to 175°C and has a resistance of 220Ω at 20°C. The fractional change in resistance per 1°C is 0.0040. The dissipation constant is 25mW/°C. Design a circuit to activate an LED alarm when the temperature reaches 150 °C. The error should not exceed +/-1°C. Use a single supply voltage.
      1. Draw a block diagram for your design. Explain the function of each block and why it is needed.
      2. Design the circuit showing all calculations. Choose standard resistor values, and specify the tolerances. Provide a drawing of your circuit with all resistor values and tolerances and parts. You may do this by creating it in Multisim and then drawing the values on as appropriate.
      3. Construct the circuit in Multisim using the resistor values you chose and tolerances. Do a screenshot showing how you have set up the tolerances for the resistors. For the RTD, you may use a potentiometer or variable resistor for which you can change the resistance for different temperatures. If you have a bridge circuit with a potentiometer for nulling, explain how you decide what resistance to use for the null.
      4. Create a table of temperature, RTD resistance, RTD resistance adjusted for self-heating, LED Status. Test your circuit, and use the table to display your results. Find the precise resistance and temperature at which the LED turns on. Provide several screenshots showing the resistance which reflects the RTD resistance value used in the circuit and the LED alarm. Which RTD resistance do you use in the circuit for testing?
      5. Put together all of the above in a well-written report including introduction, requirements, block diagram, design calculations, final design (including any potentiometer settings), testing (including which RTD resistance is used in the circuit for testing), and analysis of results. Be sure to provide a summary at the end, noting at which temperature the alarm was activated, if this was as designed, and what accounts for differences. Please note any problems you encountered.

 

PART 2

Work the problems below. To receive any credit, you must show all work. You may submit your work in a word processing document or in a pdf file. Graphic files are not acceptable submissions. Your file submission document should be entitled Week3AYourGID (replace YourGID with your specific GID).

1. What temperature in °F corresponds to 435K?
2. What is the length of a copper rod at 420K, if the rod was 93m long at 10°F?
3. Calculate the new volume for a silver cube that measures 3.15 ft on a side, if the temperature is increased from 15°to 230°C.
4. What is the resistance of a platinum resistor at 480°C, if its resistance at 16°C is 110Ω? Assume the fractional change in resistance per degree of temperature at T_o is 0.00385.
5. A type K thermocouple with an 85°F reference produces a voltage of 52.48mV. What is the temperature?
6. A thermistor has a resistance of 16.33k ohms at 0.0°C, and it drops to 6.247k ohms at 20.0°C. This thermistor is used in a simple voltage divider circuit shown below. V_s = supply voltage = 5.0 V_dc, R_s = supply resistance = 10k ohms.
   1. Calculate the output voltage at 0.0°C.
   2. Calculate the output voltage at 20.0°C
   3. Assume the output voltage is 2.353 V. Estimate the temperature given the limited amount of data provided in the problem statement.

 

 

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