1. Mechanical Measurement and Instrumentation MECN 4600
Professor: Dr. Omar E. Meza Castillo
Department of Mechanical Engineering
Inter American University of Puerto Rico
Bayamon Campus

2. Tentative Lecture Schedule
Topic
Lecture
Basic Principles of Measurements
Response of Measuring Systems, System Dynamics
Error & Uncertainty Analysis
1, 2 and 3
Sensor & Transducers
Basic Electronics, Signal Processing 4
Measurement of Pressure 5
Measurement of Temperature 6
Measurement of Fluid Flow 7
Measurement of Level 8
Measurement of Stress-Strain 9
Measurement of Time Constant 10

3. Topic 7: Measurement of Temperature
RTD & Thermistor

4. To measure temperature using a RTD & Thermistor.
Course Objectives
To measure temperature using a RTD & Thermistor.

5. RTD
Types of RTD

6. RTD RESISTANCE TEMPERATURE DETECTORS (RTDs).-
RTD’s functions as a result of increasing resistance in proportion to increasing temperature. i.e, with a known current, as temperature increases, voltage increases. As a known current is placed through the RTD, the output voltage indicates RTD resistance. Since the relationship between the resistance and temperature is known, the temperature can thus be determined.
The resistivity of the metal used in a RTD is dependent upon the temperature. Platinum has the best range and is the most common metal used.

7. Glass Wire Wound Platinum RTD Elements - Class B
Suitable for Low or very High Temperatures
Tolerant of Thermal Shocks
Good Vibration Resistance
Alpha =

8. RTD (PT100) Probes
Temperature Range -200 to 600°C
Alpha = Standard
Ro = 0°C

9. RTD The general equation is:
La ecuación general puede ser simplificada para materiales comunes como platino, cobre, etc con bajos porcentajes de error en las mediciones.

10. RTD Where: R= Resistance at temperature T
Ro= Resistance at temperature To
To= Temperature of reference
T= Temperature
α= Resistivity Coefficient

11. Theory  Experiment Circuit for the laboratory Where:
eo= Voltage through RTD
Rb= Resistance
RRTD= Resistance RTD
ei= Voltage of fem D M ei
(fem) + I Rb
RRTD eo

12. Analysis
Kirchoff’s Law:
Law of Ohm

13. Analysis
Combining previous Equations:

14. Laboratory: Find the value of α
Table of Data
Setup the circuit with a ei=10V
Measure the Ro at T=0ºC
Obtain the value of Rb
Increase temperature and measure eo
In order to find α, use the following equation
Obtain the value of α using least squared method
Compare α with values of literature.
T(ºC)
eo(V)
()