Monday, February 6, 2017

Blog Week 5

Week 5 Blog

1. Functional check: Oscilloscope manual page 5. Perform the functional check (photo).

 A picture of a successful functional test

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

 Picture of Overcompensation

 Picture of proper compensation

3. What does probe attenuation (1x vs 10x) do (Oscilloscope manual page 9)?
~~Probe attenuation adjusts the voltage of the incoming signal by increasing impedance. This is done so that more accurate measurements can be taken. The 1x and 10x designation determines to which factor the voltage decreases/impedance increases. 1x doesn't change anything, it is a 1:1 ratio. This setting is used for voltages that are small enough on their own already that they do not need to be attenuated for a more accurate reading. However, 10x decreases the incoming voltage (amplitude of the signal) by a factor of 10. This makes it much easier to take readings on the oscilloscope of signals that are higher voltages. If you have a high voltage/amplitude it is harder to see details of the signal because the scale of the Y axis would be too large. There are even higher (100x) scopes for even larger voltages.

4. How do vertical and horizontal controls work? Why would you need it (Oscilloscope manual pages 34-35)?
~~The vertical and horizontal knobs adjust the respective position of the function. By rotating the horizontal knob you can change the function along the X axis. By rotating the vertical knob you can change the function along the Y axis. This is a useful function if your function has a very large wavelength or amplitude and you are trying to see the entire wave. This is also helpful for times when the function is not directly centered in the oscilloscope.

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).
 Picture of the 1kHz wave with ~0.5 Vpp

 Picture of 1kHz and 0.5 Vpp. .25v is needed to generate 0.5 Vpp

>>b. Figure out how to measure the signal properties using menu buttons on the scope
~~After you have the function generated you have to hit the measure button at the top of the oscilloscope. Five empty CH1 boxes will appear. You can enter in values for the oscilloscope to measure by selecting the CH1 box, and switching through the menus to select the value you wish to measure.
*Note: Our function generator could only reach an offset DC value of .37 V, it would then say 'setting conflict'. When we asked Dr. Kaya he assumed our function generator was at it's max.

 Picture showing the different options of measuring

6. Connect function generator and oscilloscope probes switched (red to black, black to red). What happens? Why?
~~When you switch the cables from red to black, to black to red. The function becomes very noisy and is useless.

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)
 The Circuit of resistors in series with .5Vac and 2Vdc

For Va and Vb at the same time we got

>>b. Voltage across R4.
~~ 0.115 v

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.

 Va AC 0.119V Vb AC 0.117 V Va DC 17.6 mV Vb DC 17.3 mV

This table represents the results for Va and Vb for both AC and DC. As you can see the results we got for DC were much smaller than what we got for AC. We also know that Vb=2Va. And the difference between AC and DC is that AC is an alternating current which means that other than DC, which is direct current and only moves in one direction, the alternating current moves in two different directions. The AC Voltage we are getting is what the amplitude is, and DC we are reading the Voltage divided by the 3 resistors in parallel.

9. For the circuit below

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

Video showing how we calculated the missing R7 value

>>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.
~Alec

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 -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 showing how an inverting amplifier affects the AC sine function

>>b. Non-inverting amplifier: R1 = 1kΩ, R2 = 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 showing how an non-inverting amplifier affects the AC sine function