1. Temperature Measurement using sensors and signal conditioning
Michael Mansell
Ken Dudeck (Faculty Sponsor)

2. Topics of Discussion Types of temperature sensors
The CK101 LCD Temperature Meter
Our circuit design

3. Types of temperature sensors
RTD (Resistance Temperature Detector)
Thermistor
Thermocouple

4. RTD, the basics How it works: Make up: Temperature range:
Utilizes the fact that resistance of a metal changes with temperature.
Make up:
Traditionally made up of platinum, nickel, iron or copper wound around an insulator.
Temperature range:
From about -196°C to 482°C.
Thin Film RTD

5. RTD Advantages and Disadvantages
Stable
Very accurate
Change in resistance is linear
Disadvantages:
Expensive
Current source required
Small change in resistance
Self heating
Less rugged than thermocouples.

6. Thermistor, the basics of
How it works:
Like the RTD a thermistor uses the fact that resistance of a metal changes with temperature.
Make up:
Generally made up of semiconductor materials
Temperature Range:
About -45°C - 150°C
Thermistor

7. Thermistor Advantages and Disadvantages
Very sensitive (has the largest output change from input temperature)
Quick response
More accurate than RTD and Thermocouples
Disadvantages:
Output is a non-linear function
Limited temperature range.
Require a current source
Self heating
Fragile

8. Thermocouple, some more basics
How it works:
Made up of two different metals joined at one end to produce a small voltage at a given temperature.
Make up:
Made of up two different metals. Ex: A type J is made up of Iron and Constantan.
Temperature Range
Type J: 0°C to 750°C
A few Thermocouples

9. Thermocouple Advantages and Disadvantages
Self Powered (does not require a current or voltage source)
Rugged
Inexpensive
Simple
Disadvantages:
Extremely Low Voltage output (mV)
Not very stable
Needs a reference point

10. Lets Experiment!
In lab a RTD, thermistor, and thermocouple were placed in a beaker of 750mL of water and readings were taken from 19°C to 80°C.
The next two slides show the results.

11. The Data (some of it) Temperature Thermocouple RTD Thermistor
(degrees Celsius)
(mille-Volts)
(ohms)
(kilo-ohms) 19
-0.10
108.00
105.60 20
108.40
99.80 21
0.00
108.70
94.20 22
109.00
88.20 23
109.50
83.80 24
0.10
110.00
79.70 25
110.40
75.90 26
110.90
73.30 27
0.20
111.30
70.00 28
111.50
68.40 29
0.30
112.00
63.40 30
0.40
112.90
60.50 32
0.50
113.20
54.80 34
0.70
114.10
49.20 36
114.80
45.50

12. A little easier to read

13. First test subject (The Kit CK101)
Basically the same idea as our circuit design, but easier?
How it works
Why it did not work
CK101 LCD Temperature Sensor

14. How it works and what went wrong
Uses transistors instead of the other discussed sensor types.
Uses the ICL 7106 chip
Problems:
Possible Bad chip
Capacitors not soldered in properly.
Cold solder joins leading to bad connections

15. Our design
It works!

16. Picture

17. Another Picture

18. Circuit Diagram

19. Questions or Comments?

20. My Sources
Omega.com (Info on RTDs and Thermistors)
United Electric Controls (Thermocouple, RTD, and Thermistor info)
Intersil (ICL 7106 Chip reference)