 To show how the platinum resistance thermometer
works and how to connect it correctly.
To show the linearity of the platinum resistance
thermometer (PRT(.
To prove that the platinum resistance thermometer
is good for use as a reference temperature sensor
for all the other experiments.
⦁
The resistance thermometers use a known
change of electrical resistance in a metal for a
known temperature. The resistance
thermometers in this equipment use a thin
platinum wire or film, so they are also called
Platinum Resistance Thermometers (PRTs).
They have a positive temperature coefficient
(PTC) because their resistance increases with
temperature. A sealed metal tube with
insulation contains the thermometer for
protection against the conductive or corrosive
properties of any liquids that you put the
thermometer into.
⦁
The equipment includes two resistance
thermometers (sometimes called resistance
temperature detectors or RTDs). Both are type
PT100 - 100 Ohm at 0°C. One is the
reference temperature sensor and has a
special plug to connect to the reference
sensor socket. It uses the four wire constant
current connection for accuracy. The other is
an identical thermometer, but has four
accessible wires for use with the low voltage
connections to help show how the
thermometer works.
⦁
Connect the reference sensor to its socket
and connect the PRT to the millivolt meter
and the constant current source as shown
Note that the PRT is connected as a four wire
device.
•
Put the reference sensor and the PRT into
the icebox (through the holes in its lid). Wait
a few minutes for the readings to stabilize
and record them (the reference temperature
should be between 0°C and 1°C).
• Now put both devices into the heater tank
(through the holes in its lid). Switch on the
heater and note the reference temperature.
At intervals of 10°C (shown by the reference
temperature), record the input 1 readings of the
millivoltmeter.
• Stop the experiment and switch off
the heater when the reference
temperature reaches 100°C.
⦁
⦁
Given that the constant current is 1 mA, use
Ohm’s law to calculate the resistance of the
PRT for each row in your table.
Plot a chart of resistance (vertical axis)
against temperature (horizontal axis). Start
the vertical axis at 100 Ohm.
⦁
Add to your results table and chart, the
standard resistances given in Table 1 that
match the reference temperatures.
Find temperature coefficient α
using equation :
RF=R0(1+α(TF-T0)
We can find T at specific resistance
using equation
T= (RT-R0)/(R100-R0)×100