PHY 2049L
Lab 6 Info

AC LR Circuit Setup

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Updated: 1/1/2009

Part One (not in the lab manual)

Circuit Diagram for new experiment:
This diagram shows how the circuit should be wired up so we can measure the phase shift with the oscilloscope.

circuit diagram for part 1 of the experiment

R indicates the resistor being used (about 330 ohm).

The coaxial cable connections are already made, as shown in the pictures on the main page for this lab and below. (Be sure to push in the button to select the sine function.)

closeup of wiring of the scope, generator, and freq counter

The CH1 connection is made with the coax at the bottom left of the oscilloscope. The splitter at the top left, connected to the frequency counter with a "tee", is used to from the series LR circuit shown in the top half of the diagram. [Be careful to use the color codes and appropriate wire colors when doing this.] The CH2 connection is made with the splitter attached to the oscilloscope at bottom center. This is used to measure the voltage across the resistor R (330 ohm). [Again, notice the color codes and how they are used. The rms meter does not care how it is connected, but the phase cannot be measured correctly if you do not pay attention to the red/black sides of the circuit.]

Oscilloscope Settings

This closeup of the photo used above shows the details of the settings on the oscilloscope. When you arrive, it will probably look like this picture, which shows a scope after it was used for the previous lab experiment. The blue arrows highlight features we need to pay attention to this week.

The function generator should have the sine button pushed in. The three buttons along the buttom should all have been "out" for the previous lab, but check that they are still correct.

closeup of wiring of the scope, generator, and freq counter

The switch above the CH1 controls will have been on the CH1 setting for last week's lab. This week, we will change it to "BOTH" (to display CH1 and CH2 together) or "CH2" (if we need to adjust the CH2 display without being bothered by the other signal. The switch above the CH2 controls should be at "ALT", so that the scope will alternate between drawing a trace from CH1 and one from CH2. We will keep the trigger set on CH1, so the CH1 trace will start out as a sine function if your scope is still set up correctly from last week.

Part Two

Conversion from Part One to Part Two is fairly simple. We basically just replace the CH2 connection to the oscilloscope with the multimeter. There is no problem leaving the oscilloscope connected at CH1, so all you really need to do is to disconnect the leads from CH1 and connect them to the multimeter. Set the meter to read AC rms Volts, and then adjust the amplitude of the generator to its maximum value.

Follow the instructions in the lab manual from this point on.

Cables Available

The set of cables shown in the picture below contains the ones you will have available for this lab. The set above the meter stick includes a red-black pair of 100 cm leads and a red-black pair of 65 cm leads. One of these pairs is usually used to make connections to the multimeter while the other is used to connect to the power supply.

Full set of 9 cables used in circuit labs

The set below the meter stick includes a red-black pair of 40 cm leads, an extra 40 cm lead that is black with red connectors, and a red-black pair of 20 cm leads. The shortest cables are used for connections between nearby points on a resistor box.

Compare New and Old Setups

Setup used for this new version of the lab:

meter, boxes containing R and L, scope with generator and freq counter

Photo of the equipment as you will find it at the start of the new lab.

wave generator, freq counter, and boxes containing R and L

Photo of the equipment when we did not use the oscilloscope.


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