Lab 1 - Well-Equipped

By: Gracie Miller and Rachel Rohrer

Summary

The goal of this lab was to find values using various instruments and techniques to ensure that we understand how to use the equipment in the future. The resistance of four resistors was found, as was the capacitance of four capacitors (two ceramic and two electrolytic). The voltage being produced by a power source was tested, and the amplitude and frequency of a 2kHz sin wave produced by a function generator were measured. Each value was found using multiple instruments.

Materials

• Resistors
  • 4.7 MΩ
  • 270 kΩ
  • 82 Ω
  • 1.2 kΩ
• Capacitors
  • 100 µF
  • 10 µF
  • 1 µF
  • 0.01 µF
• JAMECO Breadboard JE27

Assembly Procedures

1. Measuring the resistance and capacitance did not require any assembly. See below for the Test Procedures of measuring the resistance and capacitance of electrical components.
2. Assembly for measuring the voltage of the DC power unit: Plug in the DC power supply and turn it on. Set output voltages of V1 and V2 to the appropriate voltage setting before measuring each.
3. For measuring the amplitude and frequency of the 2kHz sine wave: Connect the Function Generator to the proto board and to the oscilloscope. Set the Function Generator to produce a 2kHz sine wave. See below for test procedures regarding various methods to measure amplitude and frequency.

Test Equipment

• Fluke 87 True RMS Multimeter
• MY 69 Multimeter
• Global Specialties 1301A Power Supply
• Global Specialties 200kHz Function Generator 2001A
• Tektronix TDS 2012 TWo Channel Digital Storage Oscilloscope
• Precision 815

Test Procedures

Resistor Values:

For each resistor, we first read its advertised resistance using its color code. A table in Excel was used to calculate the maximum and minimum values of the resistor based on its tolerance. The DMMs were set to Ohms and their probes were placed directly (one DMM at a time) on the resistors’ wires to measure their actual resistance.

Capacitor Values:

The above method was repeated to measure the capacitance. However, the instruments used were the Fluke DMM and the Precision 815. The FLuke DMM was set to measure capacitance (Farads) not resistances (Ohms).

Voltage Values:

After turning the DC Power Supply on, it was set on V1 and the voltage was to set to +1.5V. The probes of the Fluke DMM were placed in corresponding V1 outlets and the voltage was measured. This was repeated on V1 for +7.0V and +12.5V. The power supply was then switched to V2 and values of +1.5V, +7.0V, and +12.5V were again measured. The process was repeated once more on V1 and V2 for the DC Power Supply on the 5V setting.

Amplitude and Frequency Values:

“Counting Squares”: The number of boxes from the midpoint to the peak of the sin wave on the oscilloscope were counted. This number was then multiplied by the voltage being supplied, in this case being 200mV. This was the amplitude of the wave. To determine the frequency, the number of boxes from peak to peak was counted and this number was multiplied by the period of the wave, in this case being 100s. The inverse of that value was the frequency as frequency is the inverse of period.

Cursors: The cursor function of the oscilloscope was selected, and the oscilloscope was set to the voltage reading setting. The cursors were then moved so that one was placed at the midpoint of the wave and the other was placed at the peak of the wave. The ΔV was then recorded as the amplitude of the wave. To determine the frequency, the oscilloscope was set to the period or frequency setting. The cursors were then moved so that they were placed in a peak-to-peak position, and the frequency was recorded.

Oscilloscope Features: The oscilloscope was set to read values received from channel 1. The oscilloscope displayed peak-to-trough values of amplitude, so the displayed ΔV was divided by 2 to determine from the midpoint to peak amplitude value. The frequency of the wave was directly displayed as a feature on the oscilloscope, and this value was recorded.

Generic/Fluke: The DMM probes were set to V and placed in the corresponding outlets on the proto board. In order to determine the midpoint-to-peak value of amplitude, the displayed value on the DMM was multiplied by the square root of two in order to convert from RMS. The DMMs were then set to the frequency setting and the values were recorded.

Test Results

Resistor Values:

Capacitor Values:

Voltage Values:

Amplitude and Frequency Values:

Discussion

On initial testing of the capacitors, we made an error by using the generic multimeter rather than the Precision 815. The values we found were far smaller than the values found through other means. Fortunately, we corrected our mistake at the end of the lab time and found values with the correct instrument. These values were consistent with what we had found previously. All of our measured resistance values were within the expected ranges as were the measured capacitance values. The readings from the DMMs were very near what the power source was set at. However, the DMM readings of the amplitude from the function generator did not as closely agree with the other methods of measurement. The DMMs were consistent with the other measurements when measuring the frequency.