ECE 225 Experiment #4

Power, Voltage, Current, and Resistance Measurement

Purpose: To measure V, I, and R with a Digital Multimeter (DMM) and the V with the oscilloscope; verify voltage and current division rules; investigate the effect of power dissipated by a resistor
Equipment: Agilent 54622A Oscilloscope, Agilent 34401A Digital Multimeter (DMM), Agilent 33120A 15MHz Function/Arbitrary Waveform Generator, Agilent E3631A Triple Output DC Power Supply, Universal Breadbox

  1. Power

    Accurately measure the resistance of a 27-ohm, 1/4 watt resistor. If the value is more than 5% in error ask your lab instructor for a replacement resistor. Calculate the DC voltage which results in 1/2 watt of power dissipation in the resistor, and set the DC supply to that value. Use the + and - terminals of the 6 volt output. Set the current limit to 200 mA. Attach cables from breadbox directly to the + and - terminals of the DC voltage supply. Use hookup wire to connect the resistor to the cables. Wait a few minutes and feel the resistor. Comment. Disconnect the resistor from the DC supply and measure the resistor's value and see if the value has changed as a result of the abuse. Now repeat the experiment with the DC supply set for a power dissipation of 1 watt (four times the rated amount). Don't burn yourself! Be sure to measure the resistor again before you start the 1 watt trial.

  2. Voltage Division

    For the next two parts you will need accurate values of the resistors in order to verify the voltage division and current division shortcuts. Measure these values accurately if you have not already done so. Set up the circuit in Figure 1. using the DC supply as VS. Set VS to 10 volts. Then by measuring V1, V2, V3, V4, V12, V123, and VS with the DMM , verify the voltage division rule for each of these voltages. Present your results (measured values vs. values calculated on the basis of the voltage division rule, using the accurately measured R values) in the form of a table. Next, replace the DC supply with the function generator, set it for a waveform 4sin(4000pit) volts (be sure the DC offset is zero), and repeat.

    Next, repeat all of the above measuring the voltages with the oscilloscope.

    R1 = 1.0K
    R2 = 3.3K
    R3 = 2.0K
    R4 = 4.7K

    Figure 1.

  3. Current Division

    Verify the current division rule, in a manner similar to your verification of the voltage division rule above, for the circuit in Figure 2. Let VS be 10 volts DC. Measure the currents using the DMM. No need to use the scope. The scope is a voltmeter.

    NOTE: WE WILL NOT DO AC CURRENT MEASUREMENT. THE AC CURRENTS ARE TOO SMALL TO BE MEASURED BY THE DMM IN THIS LAB.

    R1 = 1.0K
    R2 = 3.3K
    R1 = 2.0K
    R1 = 4.7K

    Figure 2.

Last modified: Tue Feb 5 13:41:42 2002