CBL
Lab 9

Measuring Voltage with a CBL

Goals: To examine low DC and AC voltages and explore the characteristics of transformer voltages

TI-83 Calculator TI CBL (with ac adapter if possible) various batteries (under 10 volts!)

TI link cable AC/AC transformer (under 7 volts!) CBL voltage probe

ACVOLT program AC/DC transformer (under 10 volts!)

Load the program ACVOLT onto your calculator from another calculator or a computer.

Attach your calculator to the CBL using a link cable. Connect the voltage probe in the channel 1 port of the CBL. Select and run the ACVOLT program on your calculator. Follow the program directions, making sure to connect the probe ends appropriately to the battery (or transformer ) terminals.

Once the time data has been collected, the program stores all collected and calculated data in the following lists on the calculator:

L1 time         L2 voltage

The program automatically displays a graph of voltage versus time. You can then use the arrow keys to examine the voltage values on the graph. When you are done with the graph, hit [ENTER].

I. Battery voltages--Use the program to look at the voltage of individual AA, C, D, AAA, 9V, or various watch batteries. (NO BATTERIES OVER 10 VOLTS!) Investigate what happens when you take the data with the probes leads reversed.

Can batteries of different physical size have the same voltage?

What happens to the voltage reading if you reverse the probe leads across a battery?

II. Batteries in series-- Look at the values marked on the batteries. Predict and then measure the voltage across 2 or 3 batteries aligned end-to-end so that their terminals line up with positve touching negative. (this is easiest with cylindrical batteries) DO NOT EXCEED 10 VOLTS TOTAL!

If you have 6 new D batteries and a radio which requires 9 volts to operate, can you get the radio to work? How? Explain.

III. AC/AC transformers-- Household wall outlets yield a 110-120volt alternating voltage. AC/AC transformers (also known as converters) take this wall voltage and decrease it to a lower voltage but leave it alternating at the same rate. Plug an AC/AC transformer (UNDER 7 VOLTS!) into a wall outlet. Measure the voltage across the transformer leads. Examine the shape of the voltage vs time graph. Examine the voltage values on the graph. Sketch the graph.

What is the time for the voltage to go through a complete cycle? Indicate how you use the graph to determine this.

How many cycles does the voltage go through in one second? Is this the value you expected?

IV. AC/DC transformers-- AC/DC transformers (also known as converters) take this wall voltage and decrease it to a lower non-alternating (more or less) voltage. Plug an AC/DC transformer (UNDER 10 VOLTS!) into a wall outlet. Measure the voltage across the transformer leads. Examine the shape of the voltage vs time graph. Examine the voltage values on the graph. Sketch the graph.

Is the voltage absolutely constant? If not, how does the variation compare with that of the AC/AC transformer voltage?

Could such a transformer run a radio that normally uses D batteries? Explain.

Connect a diode across the output leads of the AC/AC transformer. Measure the voltage. Examine the shape of the voltage vs. time graph. Examine the voltage values on the graph. Sketch the graph.

Determine the amount of time for the voltage to go through a complete cycle.

Why would the diode be called a half wave rectifier in this situation?

Connect a full-wave rectifier across the output leads of the AC/AC transformer. Measure the voltage. Examine the shape of the voltage vs time graph. Examine the voltage values on the graph. Sketch the graph.

Determine the amount of time for the voltage to go through a complete cycle.

Why is this called a full wave rectifier?

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