PASCO TD-8578 THERMAL EXPANSION APPARATUS - Manual (Page 7)

Thermal Expansion Apparatus 012-07114D
4
➃ Place the foam insulator over the thermistor lug.
➄ Plug the leads of your ohmmeter into the banana plug connectors labeled THERMISTOR in
the center of the expansion base. The banana plug connectors are located at one end of
this unit in a stop bracket.
➅ Measure and record R
rm
, the resistance of the thermistor at room temperature. Record this
value in the table.
➆ Use tubing to attach your steam generator to the end of the copper tube. Attach it to the end
closest to the dial gauge.
➇ Place a container under the other end of the tube to catch the draining water.
➈ Turn the outer casing of the dial gauge to align the zero point on the scale with the long
indicator needle. As the tube expands, the indicator needle will move in a counterclockwise
direction.
➉ Turn on the steam generator. As steam begins to flow, watch the dial gauge and the ohmme-
ter. When the thermistor resistance stabilizes, record the resistance (R
hot
) in Table 1. Also
record the expansion of the tube length (
∆L) as indicated by the displacement of the indicator
on the dial gauge. (Each increment on the dial gauge is equivalent to 0.01 mm of tube expan-
sion.)
➤Repeat the experiment for the brass and aluminum tubes.
Data and Calculations
➀ Use the Thermistor Conversion Table on page 5 of this manual or on the tag attached to the
apparatus. Convert your thermistor resistance measurements, R
rm
and R
hot
, into temperature
measurements, T
rm
and T
hot
. Record your results in the table.
➤Note: To achieve 0.2°C accuracy for temperature, you must interpolate between the
temperature values listed in the Thermistor Conversion Table.
TABLE 1 Data and Calculations
DATA CALCULATIONS
copper
brass
aluminum
L(mm) V R
rm
( ) DL(mm) V R
hot
( ) T T D T
hot
( C)
8
( C)
8
( C)
8
rm