MONTANA STATE UNIVERSITY  
DEPARTMENT OF MECHANICAL ENGINEERING                                

ETME 360 Spring 2014
Measurements and Instrumentation Laboratory
                                                    R. Larson

EXERCISE 3: 
TEMPERATURE MEASUREMENT SYSTEM EVALUATION
with COMPUTER-CONTROLLED DATA ACQUISITION   

Description: In this exercise, students write and utilize a data acquisition system program to investigate the voltage output response characteristics of a temperature measurement system. The computer-controlled system will be developed utilizing a dual-bead Type T or Type J thermocouple. The thermocouple will be subjected to a step temperature change and system response characteristics will be determined.

References:
ETME360 Lecture, ETME360 Lab Demonstration
A. Wheeler & A Ganji, Introduction to Engineering Experimentation, Chapters 3, 4, and 9.  
[Note: Review textbook discussions describing the response of 0th-, 1st-, and 2nd-order systems.]

Discussion:
When used for
dynamic measurements, thermocouple temperature measurement systems will typically exhibit a lag in response. In other words, a small amount of time may pass before the system settles on and indicates the true temperature. This lag is due primarily to the mass of the thermocouple junction,. As one would expect, more mass (larger size) requires more time to reach thermal equilibrium. Also influencing this lag time is the thermal conductivity of the materials used to construct the device, and the heat transfer characteristics of the environment. The signal conditioning and recording equipment also contributes some additional lag component. The 'time constant' is used to characterize this element of dynamic system performance. The purpose of this experiment is to gain familiarity with thermocouples and data acquisition system operation, and to be able to characterize the dynamic performance of a temperature measurement system .

Equipment:
Hot Water source, Ice Water Bath
Dual -
bead Type T or Type J Thermocouple
Digital thermometer                     
PC with LabVIEW program
National Instruments Compact DAQ Data Acquisition System                   

Prelab

Procedure

Results