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learn:instrumentation:tutorials:ad2-network-analyzer:start [2016/08/31 21:26] – [Step 2: The Network Analyzer] Marthalearn:instrumentation:tutorials:ad2-network-analyzer:start [2021/06/02 23:45] (current) – Arthur Brown
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-====== Analog Discovery 2 - Using the Network Analyzer ====== +====== Using the Network Analyzer (REDIRECT) ====== 
-When building circuits, we often need to determine how the circuit will respond given certain inputs. This is especially true when we use energy storage elements like capacitors and inductors. If you've ever looked at a circuit board, new or old, you'll often see scores of capacitors and inductors, as well as every other type of electronic component you can think of. So how do these parts interact with and change the input signal to give us the output signal? By using the network analyzer on your Analog Discovery 2 and the WaveForms 2015 software, you can get a better idea of how your circuit responds to various types of inputs.  +~~REDIRECT>test-and-measurement/guides/waveforms-network-analyzer~~ 
- +~~NOSEMANTIC~~ 
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-==== Inventory ==== +
-  * 1 [[http://store.digilentinc.com/analog-discovery-2-100msps-usb-oscilloscope-logic-analyzer-and-variable-power-supply/|Analog Discovery 2]] +
-     * You may also use the [[http://store.digilentinc.com/analog-discovery-100msps-usb-oscilloscope-logic-analyzer-limited-time/|Analog Discovery legacy]] or the [[http://store.digilentinc.com/electronics-explorer-all-in-one-usb-oscilloscope-multimeter-workstation/|Electronics Explorer Board]] with WaveForms 2015. There are some slight differences in functionality between the Analog Discovery Legacy, Analog Discovery 2, and the Electronics Explorer Board, but nothing that will prevent you from following along if you have one of the other tools. +
-  * [[http://store.digilentinc.com/waveforms-2015-download-only/|WaveForms 2015 software]] +
-  * A computer with USB port to run the software +
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-====== Step 1: Background Information  ====== +
-Inductors and capacitors are critical components in electronics, with a myriad of applications. But they will all do one of two things: either pass or block signals through them. When we look at a simple 1st order passive low-pass RC filter, we might have something like Fig. 1 below. +
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-{{ :learn:instrumentation:tutorials:ad2-network-analyzer:networkanalyzer.png |Figure 1. Passive low-pass RC filter.}} +
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-V1 represents an arbitrary frequency generator to simulate the various frequencies our circuit might encounter.  +
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-There are many other filter options out there, but we will stick with this example to stay within the scope of this tutorial. +
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-We know that this is a low-pass filter, which means that low frequency signals generated across V1 will pass through this circuit and can be read across C1. This also means that reading the output at the same location, high frequency signals will be attenuated, or dampened, by the capacitor. But why? +
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-The capacitor will charge and discharge as the voltage passing through the resistor rises and falls, but it can only do it at a limited rate or speed. At low frequency, the capacitor can charge/discharge at the same rate as the output voltage coming from the resistor, so we see no change between input and output, like Fig. 2 below.  +
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-{{ :learn:instrumentation:tutorials:ad2-network-analyzer:networkanalyzer1.png?700 |Figure 2. Change between input and output.}} +
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-It should be clear in this image that at a low frequency (10Hz) the input (yellow) and the output (blue) are nearly identical in both amplitude and phase.  +
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-As the frequency of V1 goes very large, the capacitor charges a little bit, but the voltage from V1 is already falling before it can fully charge, so the voltage starts to drop. It begins to discharge, but the voltage from V1 is once again on the rise before it can fully discharge. This cycle continues and the capacitor is continuously trying to play catch-up with the input. Since we are measuring the output as the voltage across the capacitor, what we see is greatly attenuated image of the input, as well as a noticeable phase shift between the two signals, like Fig. 3 below. +
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-{{ :learn:instrumentation:tutorials:ad2-network-analyzer:networkanalyzer2.png?700 |Figure 3. Attenuated image of the input.}} +
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-At a much higher frequency (1kHz) we see that the input (yellow) is nice and strong, but the output (blue) is much weaker and has shifted quite a bit to the right. To determine the phase shift, we multiply the frequency of the signal (10kHz) by the difference between the two peaks of channel 1 and channel 2, then multiply by 360°. By inspection we see that the peaks of the two signals aren't quite 250μs apart. We're going to call it 210μs. So we get 1000Hz * 210μs * 360° = 75.6°. Remember this value.  +
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-Oscilloscopes offer fantastic insight into how circuits behave in reference to time. A [[http://www.instructables.com/id/Transistor-Basics-BJTs/#step6|BJT oscillation circuit]] or a [[http://www.instructables.com/id/555-Timer-Basics/|555 timer IC circuit]] would be great circuits to observe over time. But as we have seen, some circuits behave differently depending on the frequency of the input signal, not how much time has passed. This is where network analyzers come in. You can see how circuits behave as you vary the frequency, regardless of time. Let's use it to determine at which frequency we start to lose signal with our low-pass filter. This is known as the cutoff or corner frequency and is extremely important.  +
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-====== Step 2: The Network Analyzer ====== +
-If you want some help with Analog Discovery 2 calibration or WaveForms 2015 installation/setup, check out this quick start [[http://www.instructables.com/id/Analog-Discovery-2-Quick-Start/|Instructables collection]].  +
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-Once you have everything set up, get it all connected and open WaveForms. Click on the "Network" button near the bottom left.  +
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-{{ :learn:instrumentation:tutorials:ad2-network-analyzer:networkanalyzer3.png?700 |Figure 4. Network button.}} +
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-This will open the Network Analyzer window. +
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-{{ :learn:instrumentation:tutorials:ad2-network-analyzer:networkanalyzer4.png?700 |Figure 5. Network analyzer window.}} +
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-Before we get started, let's look at what we see in the window. You'll see two graphs, the top shows the magnitude of our signal and has a dB scale from 10 to -90 dB on the left. The lower graph shows phase and has a degrees scale from 180° to -180°. (The vertical axis labels are on the far right of the plot windows.) The x-axis along the bery bottom of the window lists frequencies on a logarithmic scale, with major divisions at each decade of frequency. (By default, 1kHz, 10kHz, 100kHz, and 1MHz. Logarithmic scales can be a bit tricky to understand at first, but it converts the logarithmic behavior of the ciruit to a linear representation, which can be easier to understand visually. You can change between linear and log scales by clicking on the "Scale" box at the top.) At the far right you will see adjustments for the waveform generator, y-axis adjustments for each plot, and the channel adjustments. We will look more at those in a bit.  +
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-Build the circuit from the previous step, using a 1μF capacitor and 1kΩ resistor as shown. Once you have the circuit built, connect the wires as shown in Fig. 6 below. "1+" connects to "W1". "2+" connects where the resistor and capacitor meet. "1-", "2-", and the cathode (negative lead) of thew capacitor all connect to one of the black GND wires.  +
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-{{ :learn:instrumentation:tutorials:ad2-network-analyzer:networkanalyzer5.jpg?700 |Figure 6. Connect wires.}} +
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-{{tag>learn instrumentation tutorial analog-discovery-2 analog-discovery ad1 ad2 electronics-explorer eeboard oscilloscope scope waveforms-2015}}+