E1C08 09/14/2010
14:54:4 Page 369
8.14 The thermocouple circuit in Figure 8.39 is composed of copper and constantan and has an output
voltage of 6 mV for T 1 ¼ 200
C. What is T 2 ?
8.15 a. The thermocouple shown in Figure 8.40a yields an output voltage of 7.947 mV. What is the
temperature of the measuring junction?
b. The ice bath that maintains the reference junction temperature melts, allowing the reference
junction to reach a temperature of 25
C. If the measuring junction of (a) remains at the same
temperature, what voltage would be measured by the potentiometer?
c. Copper extension leads are installed as shown in Figure 8.40b. For an output voltage of 7.947 mV,
what is the temperature of the measuring junction?
8.16 A J-type thermocouple referenced to 70
F has a measured output emf of 2.878 mV. What is the
temperature of the measuring junction?
Potentiometer
Iron
Ice bath
Iron
Constantan
Measuring
junction
Reference
junction
(a)
(b)
Copper
Copper
Ice bath
Iron
Constantan
Measuring
junction
Reference
junction
Potentiometer
Figure 8.40 Schematic diagram for
Problem 8.15.
Problems 369