Monday, February 6, 2017

Blog Report Week 5

1. Functional check: Oscilloscope manual page 5. Perform the functional check (photo).
The displayed output on the oscilloscope, after the
functionality check is completed.
  • Functionality Checks help ensure that the oscilloscope and its probes are working correctly. They should be done the first time it is used, as well as if the equipment has not been used in a while or is believed to be faulty. 

2. Perform manual probe compensation (Oscilloscope manual page 8) (Photo of overcompensation and proper compensation).

Photo 1: An "overcompensated" wave 
    Photo 2: A corrected wave in
    "proper compensation" 
  • To adjust the probe, use a key to turn the screw inside of its hole until it is properly compensated on the oscilloscope's display.  

3. What does probe attenuation (1x vs. 10x) do (Oscilloscope manual page 9)?
  • Some probes differ in their attenuation setting, you can tune these settings using the mechanical switch on the handle. Be sure that the oscilloscope's attenuation matches your probe's. By adjusting the attenuation, you're actually adjusting the impedance for a more accurate reading through you probes. Ensuring that your machines settings match those of your probe, you're allowing your machine to utilize its full bandwidth.

4. How do vertical and horizontal controls work? Why would you need it (Oscilloscope manual pages 34-35)?

  • Vertical position adjusts the cursors on the oscilloscopes screen.
  • Horizontal position of all channel and math waveform, its control varies with the time base setting.
  • You can position the data from both channels, as you can choose to have them displayed separately or overlapping.
  • The Scale controls allow the user to modify the display, so that the data can be enlarged or simplified for proper reading.

5. Generate a 1kHz, 0.5 Vpp around a DC 1V 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).
The wave generated by the function generator values
displayed above.
  • We were able to generate a 0.5V Pk-Pk signal using the function generator. We adjusted the adjusted the voltage output to be about 1V, the "Auto-Set" measurements in the picture above prove this.

b.) Figure out how to measure the signal properties using menu buttons on the scope.
  • You can measure the signals properties by using the "Measure" button and adding the measurement tiles on the right side of the screen, in it you can access which channel and the type of measurement you want to monitor/record on the screen.

6. Connect function generator and oscilloscope probes switched (red to black, black to red). What happens? Why?

  • The scope does not "Auto-Set" the display correctly, it looks like there is noise mixed in with the signal, since it's signal is continuous and does not look sinusoidal. This is happening because you're connecting the oscilloscope probe to the ground, which grounds the signal before the machine can read it.

7. After calibrating the second probe, implement the voltage divider circuit below (UPDATE! V2 should be 0.5 Vac and 2 Vdc). Measure the following voltages using the Oscilloscope and comment on your results:

a.) Va and Vb at the same time (Photo)

The Va and Vb Voltages measured from the above circuit

  • The top (yellow) wave is Vb = CH1, while the bottom (blue) wave is Va = CH2. The values we used on the function generator were 1.01V for the AC (Our generator can't go below 1V) attempting to keep the [0.5 : 2]V as a ratio, we set the DC offset to 4V because of this. Also resistors R4 and R5 were not quite 1kΩ, they were actually about 1.183kΩ.
  • Notice how Va has about double the Pk-Pk Voltage compared to Vb. So when Va has the amplitude of 801V, Vb  will have an amplitude around 400V. Because the Amplitude is half that of the Pk - Pk value.

b.) Voltage across R4.
Photo 1: Attempted way of measuring Voltage across R4.
Photo 2: Using "Math" Function to find Voltage difference
across R4.

  • We attempted to directly measure the voltage across R4, but the didn't feel confident about the results because according to other blogs, you cant do this, so as a result we took the liberty to find an alternative way of measuring the voltage.
  • The "Math" measurement is set to [Math = CH1 - CH2] on the oscilloscope. This allows it to display the difference between the Pk-Pk values. So [R= Vb - Va] = [1.66V- 840mV=820mV] (O-scope says 860mV).

8. For the same circuit above, measure Va and Vb using the handheld DMM both in AC and DC mode. What are your findings? Explain.

Recorded (AC & DC) RMS Voltages - Using Handheld DMM:
  • In AC mode: Va = 2.81V, Vb = 561mV
  • In DC mode: Va = 280mV, Vb = 561mV

  • We found that the recorded DC voltage measurement for Vb doubles that of Va, what is odd is the difference between the AC voltages. From our understanding is voltage should be about the same across an entire circuit. The reason it is not is because if you attach the ground on the other side of a resistor you short the circuit, thus giving a different measurement than expected.

9. For the circuit below:

a.) Calculate R so given voltage values are satisfied. Explain your work (video)

Video explains how we calculated the resistance across R7

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 shows the measurement differences between 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). Explanations of the pin numbers are below:

a.) Inverting amplifier: Rin = 1kΩ, Rf = 5kΩ (do not forget -10V and +10V). Apply 1 Vpp @ 1kHz. Observe input and output at the same time. What happens if you slowly increase the input voltage up to 5V? Explain your findings. (Video) 

Explaining inverting amplifier circuit, and changing its voltage
  • When we re-scaled the horizontal wavelength, we noticed that the crest for CH1 took place at the same time as CH2 trough. When the input voltage is low around 1V, the output signal is a sine wave. However, this changed when we adjusted the input voltage up to about 5V, you can see that the output signal changed to more of a square step-like function wave. Pins 4 and 7 control the voltage output range on the LM741 (-10V to 10V is about 20V.) 

b.) Non-inverting amplifier: R1 = 1kΩ, R2 = 5kΩ (do not forget -10V and +10V). Apply 1 Vpp @ 1kHz. Observe input and output at the same time. What happens if you slowly increase the input voltage up to 5V? Explain your findings. (Video)

Non-inverting amplifier circuit, and what happens when we change its amplitude
  • The signal on the non-inverting amplifier, just like its name says: is not inverted. When we increased the input voltage, the output signal was not affected. This could be because the output voltage reached its maximum while we increased the input voltage. Similar to the inverting amplifier, pins 4 and 7 control the voltage output range on the LM741 (-10V to 10V is about 20V.) 


  1. In #8 I noticed that you had a reading of .253 Vac, was that Va or Vb, or were they the same? Where did you touch the probe to get these readings? I ask because we had trouble on our readings, we had very low voltage (around 25mVac).

    1. I re-edited that portion of the blog at an earlier time, updated the Va and Vb values. That voltage does seem pretty low was that for your AC? I'm assuming it was your DC, but that is odd

  2. Hey guys! It looks good, dont forget to caption all your photos and videos. I am really curious to see what your values are for number 10. We received different values for both amplifiers. Did you have trouble setting it up? We had a little difficulty but after some trial and error we finally figured it out. Just put the finishing touches on and you'll be all set!

    1. Captioned all the videos, our values for #10 were pretty straight forward, I attempted to show in the video just how increasing the amplitudes scale/positioning on the oscilloscope could show how to the input/output signals were related through and op-amp. I can't really assume what question you're referring to for the different values... thanks for the feedback though.

  3. Our oscilloscope pictures looked almost identical for almost all of the pictures, and we received the same value for #9. Also for #7b I don't know why but we only had 2 readings not 3. I would have liked to have seen a picture of your circuit for #10 because our readings were similar to yours but not identical. Good job on the blog thought it looks really good.

    1. The 3 readings is the "Math" function, we saw another group from last year use it, so decided to give it a try, theoretically it works, but measurements are only slightly off from calculated values. Unfortunately we don't have a picture, but our video for #10 is 1080p HD, if you're lucky you might be able to pause it to get a still reading. Thanks for the feedback!

  4. We recieved the same value for number 9 however I thought it was interesting that you converted the peak to peak value to a rms value we did it the other way we converted the rms value to a peak to peak value so that we could compare peak to peak values. I would encourage you to watch our video on it if you dont completely understand what im saying but once again we both got to the same conclusion so to each their own.

    1. It's funny how that equation works, i just find it easier to take the raw value of Vpp and throw it into the equation to find the Vrms value. We talked in class about our different methods before the exam, agreed that your method works just as well.