Photo 1: Operational check for the Oscilloscope
2. Perform manual probe compensation (Oscilloscope manual page 8) (Photo of overcompensation and proper compensation).
Photo 2: Proper compensation for the Oscilloscope
Photo 3: Overcompensation for the Oscilloscope
3. What does probe attenuation (1x vs 10x) do (Oscilloscope manual page 9)?
Probe
attenuation is the adjustment of the scale on which the vertical components of
the wave are displayed. The probe attenuation function exists to ensure that
the probes’ measured values are consistent with the readings on display. 10X is
the standard and 1X would limit the frequency to 7 MHz.
4. How do vertical and horizontal controls work? Why would you need it (Oscilloscope manual pages 34-35)?
Turning the nob for the vertical controls moves the wave up and down in a simple vertical shift, while the horizontal nob moves the curve left and right. This makes it easier to see the values of the curve and thus to write a function for the data.
5. Generate a 1 kHz, 0.5 Vpp around a DC 1 V from the function generator (use the output connector). DO NOT USE oscilloscope probes for the function generator. There is a separate BNC cable for the function generator.
a. Connect this to the oscilloscope and verify the input signal using the horizontal and vertical readings (photo).
Photo 4: Horizontal and Vertical reading for the Oscilloscope
By
pressing the menu buttons along the side of the display, one can view various
different values from the wave including the period and frequency and different
values for voltage including peak to peak and RMS values.
When the positive probe from the oscilloscope is connected to the red probe (positive) and the hard ground of the oscilloscope is connected to the black terminal of the function generator the oscilloscope gives a clear reading in the form of a wave. However, when the probes are reversed (ie: the positive from the function generator is connected to the oscilloscope's hard ground) the reading given by the oscilloscope is zero, or visually speaking, a flat line. This is because the hard ground is automatically zero, so when the positive end of the function generator is connected to zero, no higher value can be measured.
7. After calibrating the second probe, implement the voltage divider circuit below (UPDATE! V2 should be 0.5Vac and 2Vdc). Measure the following voltages using the Oscilloscope and comment on your results:
a. Va and Vb at the same time (Photo)
Photo: Va and Vb shown at the same time on the Oscilloscope
b. Voltage across R4.
Voltage (peak to peak) (V)
|
|
At Va
|
1.12
|
At Vb
|
2.18
|
Over R4
|
1.325
|
*Note that this circuit was done with a 1.5 V AC output and
a 2V DC offset.
Based on the theory, the voltage should be reduced by each
resistor after the positive end of the voltage source. So, the voltage at Vb
should be higher than the voltage at Va because the voltage from the source has
only been reduced by one resistor at Vb and by 2 resistors of the same value by
the time the current reaches Va. As for the value of the voltage drop over R4
it would make sense in theory that this value would be the difference between
Va and Vb, which based on these readings would be about 1.06 volts. The actual
measured reading was obviously a bit higher than this which could be accounted
for by a small change in the supplied voltage or some flow in the circuits
connections.
When measuring values for AC and DC for Va across the 1k ohm resistor, AC had a value of 1.09 Volts and DC had a value of 4.04 Volts. However when measuring the values for Vb across the 1k ohm resistor the same AC and DC Voltages were found. Because both Va and Vb are over a 1k resistor and have the same current, the voltage going though each should be the same. (After looking over other groups blogs, we realized we must have set up the circuit wrong to get values that differed so much)
9. For the circuit below
a. Calculate R so given voltage values are satisfied. Explain your work (video)
Video: R7 Calculation explained.
As the video explains, the value for R7 was calculated to be 6.1 kΩ. This is the value used in the circuit below. Note that it was constructed by putting 4 1k Ω and one 2 kΩ resistor in series.
b. Construct the circuit and measure the values with the DMM and oscilloscope (video). Hint: 1kΩ cannot be probed directly by the scope. But R6 and R7 are in series and it does not matter which one is connected to the function generator.
Video: Measuring values with the DMM and Oscilloscope
10. Operational amplifier basics: Construct the following circuits using the pin diagram of the opamp. The half circle on top of the pin diagram corresponds to the notch on the integrated circuit (IC).
a. Inverting amplifier: Rin = 1kΩ, Rf = 5kΩ (do not forget -10 V and +10 V). Apply 1 Vpp @ 1kHz. Observe input and output at the same time. What happens if you slowly increase the input voltage up to 5 V? Explain your findings. (Video)
Video : Inverted waves with increasing voltage
When the voltage is increased for the function generator, the first wave's (yellow) trough increases continuously even as far as going into the peak of wave two (blue). The second wave's peak increases until it reaches a certain point then begins to flatten out no matter the increase in voltage.
Video : Non inverted waves with increasing voltage
Similar to the inverted waves on question 10a, the first wave increases with the voltage while the second hits a certain peak value and begins to flatten out at the peak.
Some of the font sizes are larger than the questions, try bolding the questions to help readers distinguish the questions. It does not look like you calibrated your 2nd probe in the picture for #7a. For #7b, from my knowledge the voltage does not change across a circuit, the only reason you can't measure R4 is because you would be shorting the circuit before it can reach the rest of the resistors. For #10a we got a different signal output on our oscillascope when we increased our input voltage (could it possibly be cause it was un-tuned? Let me know if you ever find out, I am very curious)
ReplyDeleteI have spent a lot of time trying to figure out why you got a different value for R7 in problem 9 and therefore had to use more resistors to achieve 6.1 kiliohms but your logic seems sound and it seems a bit to large to be a rounding error. We originally calculated 6.1 killiohms as well but decided it was an error. You should watch our video and let us know what you think! Did we make a mistake?
ReplyDeleteFor number 4, we mentioned that the adjustments can aid in comparing graphs. It allows one to place two graphs right on top of each other and compare. Just a thought. For number 6, when we connected it reversed there was a very choppy static wave, not just a flat line. Why do you think this is? We had similar results with many other groups. For number 7, I believe you should have sine waves for your comparative results. Maybe your settings are off on your oscilloscope, I would look into this. I agree with your answer for number 9, however, I decided to use max values. I would assume that this means we are both right. We had very similar results with both of your op amp videos.
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