PASCO ET-8782 Energy Transfer– Thermoelectric - Manual (Page 19)

Model No. ET-8782 Experiment 2: Load Resistance and Efficiency
19 ®
Background
This section explains some of the details of the DataStudio configuration file.
Calculations: DataStudio will measure the temperature of both blocks (T
hot
and T
cold
), the voltage
across the load resistor, and the current through the load resistor. From these measurements it will
make two calculations, temperature difference (
∆T) and output power (P), using the following
equations:
∆T = T
hot
– T
cold
P = current
× voltage
Start and Stop Conditions: DataStudio has been configured with start and stop conditions, which
control when it records data. The start condition is that
∆T must drop below 35 °C. Before the
beginning of each cycle (when
∆T < 35 °
C) you will click the Start button; DataStudio will display
live data, but it will not start recording. Data recording will not start until the
∆T has increased
above 35
°
C and then dropped back below that level. The start condition will enable you to view
the temperature measurements without recording them. The stop condition will cause data
recording to stop when
∆T drops below 5 °
C.
Changing the Name of a Data Run: DataStudio will record a separate data run for each load
resistance. In order to keep track of them, you will rename each data run. By default, the runs are
named Run #1, Run #2, etc. In order to rename a run, find it in the Summary window (on the left
side of the screen), click on it once to select it, then click on it again to edit it (be careful to single-
click twice, and not to double-click). Enter the new name (for instance, “7 ohms”). When
DataStudio asks if you would like to rename all the data from this run, select Yes.
Procedure
1. Click the Start button. DataStudio will show live temperature readings in the Digits display,
but it won’t start recording yet.
2. Observe the temperature of both sides of the peltier; both should be close to room
temperature. During the experiment, you will take the peltier through several cycles of
heating and cooling. You must ensure that both sides of the peltier are close to room
temperature before each cycle starts. Note the room temperature for future reference.
3. Set the voltage on power supply to about 6 volts. Set the switch to Heat Pump mode for about
2 seconds, then return it to the neutral position. If the voltage/current sensor beeps, then the
current is too high (over 1 amp) and you should decrease the voltage (then close the switch
again to test it).
4. Set the switch to the Heat Engine position and allow the blocks to cool. Wait until both sides
are within a few degrees of room temperature. (To cool faster, install the heat sink on the hot
block and turn on the cooling fan. It also helps to put a metal object in contact with both
blocks.)