Physics307L F08:People/Trujillo/LAB NOTEBOOK/070827

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Oscilloscope Lab

Test Conditions

I am using old function generator to produce a 2KHz Sine/Square wave. The output of the function generator is connected to a BNC "T" which splits the signal into in 2 defendant signal. The output signals are then connected to channel 1 & 2 of at lunch box tek scope. Both Channels are initially DC coupled


1. Measurements

The first measurements I performed were voltage peak to peak, frequency, rise and fall time on both channel 1 and channel 2. To maximize the accuracy of the measurements I adjusted the SEC/DIV knob allowing me to "Zoom" in to focus on 2 full transitions.

Channel 1 Measurement Results 

  Peak to Peak        6.96V
  Frequency           2.005KHz
  Rise Time           345.3ns
  Fall Time           350.2ns

Channel 2 Measurement Results 

  Peak to Peak        7.04V
  Frequency           2.005KHz
  Rise Time           346.3ns
  Fall Time           345.2ns

2. Triggering

Triggering is a mechanism that allows data capturing on an O-Scope. There are tons of different ways the Tek scope can trigger. The most common way to trigger the scope is threw a software trigger (Auto Trigger) which will allow data capture no matter what type of signal is at the input and require no triggering condition. When the scope is set to "Normal" trigger, the scope waits to capture data until all trigger conditions are satisfied such as triggering level (the voltage level where the signal to measured is valid), trigger edge (The starting edge where the data will begin capture) which is the same as polarity. I experimented with changing the trigger sources from channel 1 to channel 2. Did some forced capture and fiddled with the trigger levels

3. AC\DC Coupling

To show how AC and DC coupling affected my output measurement, I applied a square wave (which has a DC component) and simply switch DC coupling to AC. Since I had a square wave that was going over 2KHz, I could not see the affects to switching to a low pass filter. By decreasing the frequency, I was able to see how the the AC coupling cuts out the DC component of the square wave. The rise time of the signal whos DC components were cut off was about 3 OOM slower then when DC coupled

4. FFT

Stands for Fast Fourier Transform and is used to analyze the frequency domain details of the measured signal. The Tek scope has this "Transform" under the math functionality. When displayed, the FFT looks kinda like a histogram (it kinda is). There are a number of separate special measurements that can be taken when this math function is enabled (I dont really know the details SINAD ENOB THD etc.).


Summary

I think this lab session was very informative and organized well.. I was particularly greatful for the help I received from the TA helping me calculate tao in the exponential decay associated AC coupled square wave. I still didn't quite understand the relevance but luckily the math was strait forward. Having a good amount of experiance with O-Scopes I don't have too much to say or ask.. Oh, I was not able to find the -/+ percent error on the measurements I took. I dont think I quite understood the process. I think I was supposed to take multiple measurements then take the average to find the % error.

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