VAL JOHN C. MENDOZA
SEPTERMBER 8, 2021
BSEE 4A
RESISTANCE TEMPERATURE DETECTOR
INTRODUCTION
Temperature is one of the factors that can affect the amount of
resistance a conductor may have. By definition, is a measure of the average heat
or thermal energy of the particles in a substance or simply the hotness or coldness
of a substance. Resistance, on the other hand, of an object is the measure of
opposition to the flow of electric current. Resistance also varies accordingly with
materials used in a certain conductor. This is justified by the equation:
R = ρl/A
Where 'R' is resistance of the metal, 'ρ' is the resistivity of the metal, 'l' is
the length of the metal and 'A' is the area of cross section of the metal.
With the use of Resistance Temperature Detector (RTD) we will be able
to know how temperature and resistance is related to each other with different
materials used. These are the materials commonly used in RTD; includes
platinum, copper, nickel, balco, tungsten. Temperature increases directly with
resistance, this is justified by the equation:
Rt = R0[1+ α (t-t0)]
Where:
Rt =
resistance
at
temperature
't'
R0 = resistance at a reference temperature ( Generally 0 degree C)
α = temperature coefficient of resistance (°C‾1)
RTD materials must have the following criterion; malleability to form
small wires, linear relationship of resistance and temperature, repeatability
and stability, corrosion, low cost, and easy availability. In addition to this, the
specifications of RTD performance includes temperature coefficient, accuracy,
stability, interchangeability, response time, insulation resistance, and selfheating.
EXPERIMENT
These are the data I gathered and collated after I’ve done the
experiment using Resistance Temperature Detector by Sensor Analysis
Laboratory.
The first level is the Static Characteristics which is to select R0 given a
material to get the temperature. With all those information, Rt values will be
determined. All the data gathered were verified and computed using calculator
to ensure that the values are correct.
For platinum used as material:
R0
100
200
T(°C)
523
122
791
88
352
384
Rt
301.36
146.97
404.54
267.76
471.04
495.68
For copper used as material:
R0
100
200
T(°C)
16
238
70
152
-67
-55
Rt
106.832
201.63
129.89
329.808
142.78
153.03
For the second level which is the dynamic characteristics of an RTD, the
students are assigned to select an RTD as bare element, with sheath, and
thermowell which is performed in three separate experiments.
These are the data gathered for RTD as bare element. Platinum RTD is
used in this experiment to obtain or compute for the time constant values.
The time constant value for this is 1.17 seconds.
For the with sheath, these are the data gathered:
Material
Platinum
With
Sheath
SS 304
SS 316
SS 410
.5
2.72
2.71
2.39
.75
3.42
3.41
2.92
Thickness (mm)
1
4.13
4.11
3.46
1.5
5.53
5.51
4.53
2
6.94
6.91
5.61
For the thermowell, these are the data collated:
Material
P
L
A
T
I
N
U
M
Thermowell
Thickness
Filling Material
.5
S
S
.75
1
3
0
4
1.5
2
Output
8.52
Mg
O
P
O
W
D
E
R
Using SS 304 as material and MgO powder as filling material
`
9.93
11.33
12.74
Material
P
L
A
T
I
N
U
M
Thermowell
S
S
Thickness
Output
.5
36.23
.75
`
1
3
0
4
Filling Material
SILICON
COMPOUND
37.63
1.5
39.04
2
40.45
Using SS 304 as material and Silicon Compound as filling material
Material
P
L
A
T
I
N
U
M
Thermowell
Thickness
Filling Material
.5
S
S
.75
1
3
1
6
1.5
2
Output
8.51
Mg
O
P
O
W
D
E
R
`
9.91
11.31
12.71
Using SS 316 as material and MgO powder as filling material
Material
P
L
A
T
I
N
U
M
Thermowell
Thickness
S
S
.5
36.22
.75
`
3
1
6
1
Filling Material
SILICON
COMPOUND
Output
37.62
1.5
39.02
2
40.42
Using SS 316 as material and Silicon Compound as filling material
Material
P
L
A
T
I
N
U
M
Thermowell
Thickness
Filling Material
.5
S
S
.75
1
4
1
0
1.5
2
Output
8.19
Mg
O
P
O
W
D
E
R
`
9.26
10.33
11.41
Using SS 410 as material and MgO powder as filling material
Material
P
L
A
T
I
N
U
M
Thermowell
S
S
Thickness
Output
.5
35.89
.75
`
1
4
1
0
Filling Material
SILICON
COMPOUND
36.97
1.5
38.04
2
39.12
Using SS 410 as material and Silicon Compound as filling material
CONCLUSION
In this experiment, I found out that the resistance of an object is directly
proportional to the temperature. When the temperature is being increased,
the resistance also increases. The resistance of an object also depends on
what material is being used. Just like platinum and copper, because their
temperature coefficient of resistance also varies.
For the second level of experiment, the time constant value for bare
element platinum is 1.17 seconds. The time constant values of RTD varies
directly as the thickness. When the thickness increases, the time constant
values also increase depending on what type of material is used, whether SS
304, SS 316, or SS 410. For SS 304, SS 316, and SS 410 and MgO used as
filling material, as thickness increases, time constant values also increase. But
when these materials have silicon compound as their filling material, the
response time of RTD is now 5 times the time constant values. The values of
response time and time constants vary with the materials used for bare
element, with sheath, and thermowell. These values also changes as filling
materials also change.