Temperature Measurement using sensors and
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Transcript Temperature Measurement using sensors and
Temperature Measurement using
sensors and signal conditioning
Michael Mansell
Ken Dudeck (Faculty Sponsor)
Topics of Discussion
Types of temperature sensors
The CK101 LCD Temperature Meter
Our circuit design
Types of temperature sensors
RTD (Resistance Temperature
Detector)
Thermistor
Thermocouple
RTD, the basics
How it works:
Make up:
Utilizes the fact that
resistance of a metal
changes with
temperature.
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
RTD Advantages and Disadvantages
Advantages:
Stable
Very accurate
Change in
resistance is linear
Disadvantages:
Expensive
Current source
required
Small change in
resistance
Self heating
Less rugged than
thermocouples.
Thermistor, the basics of
How it works:
Make up:
Like the RTD a
thermistor uses the fact
that resistance of a
metal changes with
temperature.
Generally made up of
semiconductor
materials
Temperature Range:
About -45°C - 150°C
Thermistor
Thermistor Advantages and Disadvantages
Advantages:
Very sensitive (has
the largest output
change from input
temperature)
Quick response
More accurate than
RTD and
Thermocouples
Disadvantages:
Output is a nonlinear function
Limited
temperature range.
Require a current
source
Self heating
Fragile
Thermocouple, some more basics
How it works:
Make up:
Made up of two
different metals joined
at one end to produce
a small voltage at a
given temperature.
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
Thermocouple Advantages and Disadvantages
Advantages:
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
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.
The Data (some of it)
Temperature
(degrees Celsius)
Thermocouple
RTD
Thermistor
(mille-Volts)
(ohms)
(kilo-ohms)
19
-0.10
108.00
105.60
20
-0.10
108.40
99.80
21
0.00
108.70
94.20
22
0.00
109.00
88.20
23
0.00
109.50
83.80
24
0.10
110.00
79.70
25
0.10
110.40
75.90
26
0.10
110.90
73.30
27
0.20
111.30
70.00
28
0.20
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
0.70
114.80
45.50
A little easier to read
RTD
3.50
135.00
3.00
130.00
Resistance (Ω)
2.50
2.00
1.50
1.00
0.50
125.00
120.00
115.00
110.00
105.00
0.00
100.00
-0.50
0
10
20
30
40
50
60
70
80
0
90
10
20
30
40
50
Temperature (∘C)
Temperature (∘C)
Thermistor
120.00
100.00
Resistance (KΩ)
Voltage (mV)
Thermocouple
80.00
60.00
40.00
20.00
0.00
0
10
20
30
40
50
Temperature (∘C)
60
70
80
90
60
70
80
90
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
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
Our design
It works!
Picture
Another Picture
Circuit Diagram
+
-
1
1K
2
50K
7417
49K
+
-
Vin
+
Thermocouple
+
Vout
4.7μF
+
1K
5V
+
-
1K
50K
1K
Relay
15V
50K
Fan
Questions or Comments?
My Sources
Omega.com (Info on RTDs and
Thermistors) http://www.omega.com/
United Electric Controls
(Thermocouple, RTD, and Thermistor
info) http://www.ueonline.com/
Intersil (ICL 7106 Chip reference)
http://www.intersil.com/