You are designing a sensing circuit that uses Platinum RTD sensors (Ro = 100 2 at 0C; a= 3.92x10-4 C-4) to measure temperature of the engine coolant in a motor vehicle, in the range 0C to 100C. You are going to design a measurement system that will be interfaced to an AD converter (8-bit, 0 to +10 volts). The RTD is located in the engine cavity, and the remainder of the measurement system is remote from the engine to minimise EMI. As a voltage source for your measurement system, you use the 12 volt vehicle battery. 1. Explain the principle of operation of an RTD, and any precautions that you need to take in its use. [3 marks] 2. Design a measurement system to obtain a linear relationship between the output voltage input to the ADC and the input temperature variation. You must include relevant analysis to show the performance and operation of your system. Note that you are free to choose any circuit configuration, as long as it satisfies the system specifications. [3 marks) 3. Determine the transfer function of your temperature measurement system. Include an analysis and discussion of the sensitivity and linearity of your system. Comment on the result, where appropriate. [3 marks] 4. What is the minimum detectable temperature change that the A-to-D card can resolve? (3 marks) 5. As a result of inductive coupling, a 10 kHz noise signal is added to the signal coming from the thermistor. Design an active filter to remove this noise, but not affect the low frequency signal from the RTD. [3 marks] You are designing a sensing circuit that uses Platinum RTD sensors (Ro = 100 2 at 0C; a= 3.92x10-4 C-4) to measure temperature of the engine coolant in a motor vehicle, in the range 0C to 100C. You are going to design a measurement system that will be interfaced to an AD converter (8-bit, 0 to +10 volts). The RTD is located in the engine cavity, and the remainder of the measurement system is remote from the engine to minimise EMI. As a voltage source for your measurement system, you use the 12 volt vehicle battery. 1. Explain the principle of operation of an RTD, and any precautions that you need to take in its use. [3 marks] 2. Design a measurement system to obtain a linear relationship between the output voltage input to the ADC and the input temperature variation. You must include relevant analysis to show the performance and operation of your system. Note that you are free to choose any circuit configuration, as long as it satisfies the system specifications. [3 marks) 3. Determine the transfer function of your temperature measurement system. Include an analysis and discussion of the sensitivity and linearity of your system. Comment on the result, where appropriate. [3 marks] 4. What is the minimum detectable temperature change that the A-to-D card can resolve? (3 marks) 5. As a result of inductive coupling, a 10 kHz noise signal is added to the signal coming from the thermistor. Design an active filter to remove this noise, but not affect the low frequency signal from the RTD. [3 marks]
