ME345_Lecture_34

# ME345_Lecture_34 - in a tank The resistance is measured to...

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M E 345 Spring 2008 Professor John M. Cimbala Lecture 34 04/09/2008 Today, we will : Do some more example problems – temperature measurement Continue to review the pdf module: Temperature Measurement Discuss an additional item not in the pdf notes: temperature compensation Example Given : Fred uses a type K thermocouple to measure the temperature in a freezer. The actual ( true ) temperature in the freezer is T 1 = -200.0 o C. The thermocouple voltages are measured properly with an ice bath reference. Unfortunately, the ice bath has too much water, and its temperature is actually 1.00 o C instead of 0.00 o C. Fred is not aware of this – he assumes that the ice bath is at 0.00 o C. To do : Calculate the temperature that Fred measures, and the percentage error. Solution :

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Example Given : A standard 100- Ω platinum RTD is used to measure the temperature of warm air

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Unformatted text preview: in a tank. The resistance is measured to be 125.9 Ω . To do : Calculate the temperature of the air in the tank. Solution : A standard 100-Ω platinum RTD means that the resistance is 100 Ω at T = 0 o C. Example Given : A standard 100-Ω platinum RTD is used to measure temperature. A Wheatstone bridge is set up in the three-wire configuration, using resistor R 3 as the RTD, as sketched. • R lead = 0.51 Ω at 20 o C • V s = 10.00 V • We want the bridge to be exactly balanced when T = 20 o C ( a ) To do : What resistors ( R 1 , R 2 , and R 4 ,) should we use to balance the bridge at 20 o C? ( b ) To do : At T = 40 o C, predict V o . Note : At 40 o C, R lead increases slightly to 0.54 Ω . Solution : V s = supply voltage R 1 R 2 R 4 R lead V o + − + − R 3 = RTD R lead R lead...
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ME345_Lecture_34 - in a tank The resistance is measured to...

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