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This document serves as a User’s Guide for the ALICE Desktop software interface written for use with the ADALM active learning kit hardware. If you are looking for ALICE for the ADALM (M1K) look here.

Although the word ALICE can be spelled out from the title of this users guide, it is actually an allusion to the fantasy works of Lewis Carroll: ’s Alice’s Adventures in Wonderland and its sequel Through the Looking-Glass, and What Alice Found There. In these stories Alice explores a strange and wondrous world down a rabbit hole and on the other side of a mirror ( looking glass ).

Hopefully, through the use of this software along with the ADALM active learning module hardware, Students can explore the strange and wondrous world of Circuits, Electronics and Electrical Engineering.

The ALICE M2K Desktop software provides the following functions:

• Two Channel Oscilloscope for time domain display and analysis of voltage and current waveforms.
• Two Channel Arbitrary Waveform Generator (AWG) controls.
• X-Y display for plotting captured voltage vs voltage and math data as well as voltage waveform histograms.
• Two Channel Spectrum Analyzer for frequency domain display and analysis of voltage waveforms.
• Bode plotter and network analyzer with built-in sweep generator.
• Impedance Analyzer for analyzing complex RLC networks and as a RLC meter and Vector Voltmeter.
• DC Ohmmeter, measures unknown resistance with respect to known external resistor.

The ALICE Desktop program for the ALM is written in Python and if run from the source code requires version or greater of Python be installed on the user’s computer. The program only imports modules generally included with standard Python installation packages.

Windows users who do not wish to install Python and the other required software packages can install and use the standalone executable by:

Run the www.cronistalascolonias.com.ar installer program. ALICE M2K desktop opens and saves info and data to various files in the installation directory. Because of user permission issues with some installations of Windows you may need to install the software in a directory other than the default “Program Files”. C:\ALM Software\M2K would be a good second choice. If you also have ALICE for the ALM installed be sure to install ALICE for the ALM in a different directory because they use similar file names to save info and would likely conflict with each other. The installer adds desktop icons for each tool in the suite. Alternatively, under the properties for the icons, you can change the directory the program(s) start in.

Or run ALICE Desktop from the Python compatible source code with the following packages installed:

Python (or higher, 32 bit version recommended)
numpy numerical package extension
libiio and www.cronistalascolonias.com.ar

Most releases of the Linux operating system have Python included and many also include the numpy numerical package as well. Linux ( including Raspberry Pi ) and OSX users must manually compile libiio library. Direction on how to manually install Numpy can be found here.

To manually install on Windows download, www.cronistalascolonias.com.ar from the libiio page on GitHub. The USB drivers will also need to be installed by downloading the plutosdr-m2k-drivers-win from GitHub. For OS X and Linux users there are installer versions of libiio for popular distributions of the OS in GitHub. The command(s) to manually build things are shown on the GitHub page as well. You will also likely need the development version of python installed ().

Raspberry Pi users with Raspbian need to have the Jessie distribution installed which includes the most up to date versions of gcc ( ) and libusbdev (). As with other Linux OS the command(s) to make things are shown in the GitHub Readme. You will also need the development version of python installed (). Cmake may also need to be installed if it has not been done already ().

For Linux users, numpy might already be part of your Python distribution. Otherwise you can download and install numpy through the software / package manager on your particular version of Linux.

For Windows users, there are Windows binary installers that can be downloaded from SourceForge. The latest version may or may not have a Windows binary so you may need to look back one or two version releases to find a Windows binary. As of this writing the newest version with a binary is numpywinsuperpack-pythonexe Be sure to download the version for Python ! Note that the developers have only created a Windows binary for 32 bit Python Users more familiar with building from source code can download the source archive and use the setup scripts to install ( build ) numpy for their 64 bit version of Python.

It is assumed that the reader is somewhat familiar with the functionality and capabilities of the ADALM hardware. For more on the ADALM hardware please refer to the following documents:

ADALM Overview
ADALM Hardware
ADALM Design Document
ADALM Analog Inputs

Below for reference is the pinout for the ADALM connector.

The Windows executable installer, in addition to the main ALICE Desktop program, includes the following DC measurement tools:

Be sure that the ALM board is plugged into a USB port before starting the program. The program performs an internal self calibration upon startup. Nothing should be attached to the Scope inputs or AWG outputs for the few seconds while the self calibration is running. Once the program is running the main window, as shown in figure 1, should appear. This is the main desktop window and serves as the Oscilloscope Tool Window as well as controls for opening the other display windows and certain common control functions. It is sub divided into 4 sections.

Many of the drop down menus on the main oscilloscope screen and the screens for the other instruments include accelerator keys, indicated by [] around the accelerator keyboard character next to the menu item. Typing one of these characters while the mouse cursor is inside the graphics drawing area will invoke that menu function. For example typing 1 or 2 will toggle on and off the CH1 and CH2 traces.

The Green Conn button in the top row indicates that a ALM board is connected and ready to go. If the button is red and says Recon then a ALM board was not found. Connect board and click on the button to connect to board.

The File drop down menu lists commands for saving and loading configuration settings (.cfg file). Save config does not save waveform data. Only the values of the various controls and settings etc. Which windows are open and where they are placed on the computer screen is also saved. When you Exit ALICE the program saves the configuration in a file named “www.cronistalascolonias.com.ar”. When ALICE is restarted this configuration is reloaded so the program will be set up as it was when last exited. ALICE also has a feature to read an init file that can set the sizes of the graphics display areas and the trace colors etc upon start-up ( see the section at the end of this document on configuring ALICE for more details ).

On most operating systems there is a way to capture a bit map graphic of any of the display windows at any time. Some are built in or done through a support program or application. In Windows:

Press the <alt> and <printscreen> keys to capture the currently selected window in the copy buffer (clip-board). Then start a program such as Word or Paint (any similar program). Use Paste to place the screen shot into your document or drawing etc. Then save that file to disk.

It is possible to save the graphics display area to an encapsulated postscript file (.eps). This is used to save a graphics file to be included in another program like a word processor to write a Lab report. It is also possible to save the captured channel 1 and 2 voltage signal data to a coma separated values file (.csv). For most Time/Div settings the number of sample points is 2 screen widths with a minimum of 2, samples and a maximum of 16, The sample rate and number of samples in the buffers changes based on the Time/Div setting. This saved table of raw sample values can then be loaded into other programs for analysis such as a spreadsheet program or numerical processing program like MATLAB, or Octave. Similarly, it is possible to load in trace data into the channel 1 and 2 voltage signal data buffers from a saved csv file. This only works when stopped. If the green Run button is pressed new data is captured over writing the data that was loaded from the file.

The Options drop down menu, figure 2, lists a command for enabling smoothing where spline curves are used to connect the input sample points rather than the default straight lines. A second option for connecting the sample points is to use a zero order hold function where a horizontal line and a vertical line are used. This looks like a stair step waveform much like the output of the Digital-to-Analog converters used to generate the AWG output signals actually produce.

The Trace Avg button turns on trace averaging. The number of sweeps to average can be set with the Num Avg button. The width of the traces in pixels can be set with the Trace Width button.

The currently displayed traces will be saved via the Snap-Shot option as reference traces. They can be added to the graphics plot area by selecting the desired trace from the Curves drop down menu for time plots. They will be drawn in a darker color corresponding to the matching live waveform trace.

The Graphics display area can be drawn with either a Black (default) or White background. Use these two buttons to select which is used. The last option buttons start the self calibration procedure, and allow the user to save or load the current calibration correction factors to a file. Nothing should be attached to the Scope inputs or AWG outputs for the few seconds while the self calibration is running. See later section for more details.

The C1 and C2 measure drop down menus, figure 3, list which vertical measurements for the Channel 1 and 2 voltage signals are to be displayed along the bottom of the graphics display area.

The displayed vertical measurements can be the following:

• Average, which is the sample by sample sum of the data record divided by the number of samples. For most Time/Div settings the number of samples is 2 screen widths.
• Minimum, which is the minimum value within the data record.
• Maximum, which is the maximum value within the data record.
• Base, used mainly for square waves it is the voltage level of the lower flat portion of the wave which may be different from the Min value due to undershoot.
• Top, used mainly for square waves it is the voltage level of the upper flat portion of the wave which may be different from the Max value due to overshoot.
• Midpoint, which is the maximum value plus the minimum value divided by two.
• Peak-to-Peak, which is the maximum value minus the minimum value.
• RMS, or True RMS which is the square root of the sum of the sample by sample data record squared divided by the number of samples.
• C1-C2 and C2-C1 differences of the Average ( DC ) voltage values of the channels.
• The true RMS value of the sample by sample difference of the channel 1 and channel 2 voltages ( RMS)
• Display User defined measurement.

The displayed horizontal measurements for the voltage traces can be the following:

• High pulse width ( time waveform is above the mid-value )
• Low pulse width ( time waveform is below the mid-value )
• Duty Cycle ( percent of time waveform is High )
• Period ( time between 2 rising edges where waveform crosses mid-value )

Figure 3g shows examples of many of the possible waveform measurements. Six of the vertical measurements are derived directly from the waveform data array. These are Avg, Min, Max, Top, Base and RMS. The rest are calculated from these six. P-P is obviously Max – Min. Mid is (Max + Min / 2). C1-C2 is C1 Avg – C2 Avg.

The User measurement option allows the user to calculate any other measurements based off these constants. When clicked on the user is prompted for a label to be used while displaying the value and a formula for calculating the value. Clicking on Cancel for either the label or formula turns off the display of the User measurement.

For example the overshoot can be calculated by the formula:

(MaxV1 –VATop)/(VATop-VABase)

A second example would be the gain of a circuit where channel 1 is considered the input and channel 2 is the output. The gain would be the ratio of the two P-P values:

(MaxV2-MinV2)/(MaxV1-MinV1)

A third example is to calculate the rms value of just the AC portion of a signal. The built-in True RMS calculation includes any DC offset component. To remove the DC portion and just display the rms value of the AC portion of Channel 1 you can use the following formula:

www.cronistalascolonias.com.ar(SV1**2 - DCV1**2)

The Crest factor can be calculated which is the ratio of peak-to-RMS values. The crest factor for single frequency sine waves is (1/), but can be as high as five or more for random noise. The crest factor for the channel A waveform would be the ratio of the Max and RMS values:

MaxV1/SV1

Another common waveform calculation is the peak-to-average ratio or PAR.

MaxV1/DCV1

Two more examples are to calculate the Peak positive and negative slew rates. The Numpy ediff1d function takes the differences between consecutive elements of an array. We can use this to calculate the dv/dt or the time rate of change between samples. Each sample is 10 uSec apart so we get V/10uS or we can divide by 10 for V/uS or multiply by for V/mS. We can then use the Numpy max or min function to find the positive ( maximum ) slew rate or the negative ( minimum ) Slew Rate using the following formulas:

www.cronistalascolonias.com.ar(www.cronistalascolonias.com.ar1d(VBuffA))* or
www.cronistalascolonias.com.ar(www.cronistalascolonias.com.ar1d(VBuffA))*

We can extend this calculation to estimate the rise and fall times for square wave signals assuming a more or less constant ( peak ) slew rate between the 10% to 90% levels. If we divide ( 80% ) times the peak-to-peak value of the waveform by the peak slew rate we get the rise or fall times.

(MaxV1-MinV1)* / (www.cronistalascolonias.com.ar(www.cronistalascolonias.com.ar1d(VBuffA))*) or
(MaxV1-MinV1)* / (www.cronistalascolonias.com.ar(www.cronistalascolonias.com.ar1d(VBuffA))*)

If the waveform has significant overshoot or undershoot you could alternatively use the VATop and VABase values rather than the Max and Min values.

Waveform calculated Vertical measurement scalars:

DCV1 is the channel 1 Average voltage
MinV1 is the channel 1 Minimum voltage
MaxV1 is the channel 1 Maximum voltage
VATop is the channel 1 Top voltage
VABase is the channel 1 Base voltage
SV1 is the channel 1 RMS voltage
DCV2 is the channel 2 Average voltage
MinV2 is the channel 2 Minimum voltage
MaxV2 is the channel 2 Maximum voltage
VBTop is the channel 2 Top voltage
VBBase is the channel 2 Base voltage
SV2 is the channel 2 RMS voltage

Waveform calculated Horizontal measurement constants:

CHAHW is the channel 1 High Pulse Width
CHALW is the channel 1 Low Pulse Width
CHADCy is the channel 1 Duty Cycle
CHAperiod is the channel 1 Period
CHAfreq is the channel 1 Frequency
CHABphase is the channel 1 to channel 2 relative phase angle
CHBHW is the channel 2 High Pulse Width
CHBLW is the channel 2 Low Pulse Width
CHBDCy is the channel 2 Duty Cycle
CHBperiod is the channel 2 Period
CHBfreq is the channel 2 Frequency

The Math drop down menu, figure 4, lists which sample point by sample point calculated waveform combining the Channel A and B voltage and current signals is to be displayed vs time.

One of the following built-in calculated waveforms can be displayed at a time:

• C1-V + C2-V, the sum of the channel 1 and 2 voltage waveforms
• C1-V – C2-V, the difference of the channel 1 and 2 voltage waveforms
• C2-V – C1-V, the difference of the channel 2 and 1 voltage waveforms
• C2-V / C1-V, the ratio of the channel 2 voltage and channels 1 voltage waveforms which is instantaneous voltage gain assuming C1-V is input and C2-V is output

The first three calculations result in voltages and share the corresponding left side voltage scale on the display grid. The final ratio calculation can be used to calculate voltage gain and is dimensionless.

If Formula is selected then the mathematical formula entered with the Enter Formula button, will be plotted vs time. This allows greater flexibility in waveform plotting at the expense of typing in the function to be plotted. See section on Advanced Math Traces below on how to enter formulas. Any one of the four channel vertical axis controls can be chosen for the Formula axis using the Math Axis button. Generally when plotting using Formula, one or the other of the four channels are not being displayed and its axis controls will be available to be used.

The AWG control Window is opened by default when the program is started. Since all of the displays use the AWGs in some fashion, it is important that this window be available to all. If you dismiss ( minimize to the tool bar ) the AWG control window, clicking on the AWG Window button will bring back the window.

The X-Y Plots Window button opens the X vs Y display window.

The Spectrum Window button opens the Spectrum Analyzer display window.

The Bode Plot Window button opens the Bode Plot display window.

The Impedance Window button opens the Impedance Analyzer display window.

The DC Ohmmeter Window button opens the DC Ohmmmeter display window.

To update the display window for a particular tool ( when running ) the matching Time Plot, X-Y Plot, Freq Plot, Bode Plot and/or Impedance Plot enable check boxes must be selected. More than one display can be selected at a time but some combinations such as X-Y and Spectrum or X-Y and Impedance would not make much sense while Time and X-Y or Time and Spectrum might.

The external positive and negative User power supply values can be set here. The positive supply can be set to any value from to volts and the negative supply can be set from to volts. The supplies can be turned on and off as well. The background of the check boxes changes from red (Off) to green when the supply is turned On.

At the bottom of this section, just above the ADI logo, are entry windows which allow input gain and offset adjustments or corrections for any external resistor divider attenuator networks that might be added to the channel 1 and 2 inputs. Save and Load Adj buttons can be found under the File drop down menu. For more on the use of input attenuators please refer to the following two documents:

M2K Analog Inputs
M2K Breadboard Adapters

The menu section along the top contains various buttons and drop-down menus that control Oscilloscope Triggering, Horizontal time base, Horizontal position, how and what signals are displayed, and run acquisition looping / stop acquisition looping / exit program.

The Trigger button is a drop down menu listing which signal to trigger on, C1-V, C2-V or none. The use of Triggering to display a stable trace is generally necessary when viewing signals.

The Auto Level option automatically sets the trigger level to the selected waveform midpoint on each sweep. The trigger point will thus track any changes in the input waveform. The Single shot option allows a single sweep to be captured each time the Run button is clicked.

The Edge button is a drop down menu listing either the rising or falling edge for triggering. The Trigger Level entry window contains the trigger level in volts for C1-V and C2-V. The 50% button sets the trigger level to the midpoint (50% point) of the selected trigger waveform. i.e. to the (maximum + minimum)/2.

The Hold Off entry window, in mS, is used to shift the horizontal position ( apparent time 0 start point ) within the acquired sample point buffers being displayed. The data used for the vertical and horizontal waveform calculations is also shifted by that amount. The sample buffer is generally two screens long so setting the hold off time to more than one screen width is not recommended.

The Horz Pos entry window is used to change the horizontal position of the time trace. Normally, with the Horz Pos set to 0 the left edge of the grid is “time 0”. Setting Horz Pos to something else shifts the 0 time point on the grid by that amount ( in mSec ). So if you set Horz Poss to a negative number for example you can see time before the trigger.

The Time mS/Div spinbox entry window is used to set the horizontal time base in the standard 1, 2, 5 step increments. Other values maybe entered manually.

The Curves button allows the selection of which signal waveforms will be displayed when plotting vs time. The All button selects both channel&#;s curves to be displayed and the None button clears all curves. The loop Back option allows the used to display the signals at the two AWG outputs without needing to move the scope channel input connections. Internal switches disconnect the + input signal paths and redirect them to the AWG outputs and the - inputs are grounded. It is also possible to select which of the possible stored reference time traces, if saved via the Snap-Shot option, will be displayed. The time and voltage cursors are turned on and off here as well.

It is good practice to turn off the supplies ( or better yet disconnect them ) when making any modifications to the circuit under test.

The green Run button starts continuous looping acquiring input samples. The red Stop button stops or pauses the acquisition looping. The Stop button also serves as a sort of refresh button. If the Stop button is clicked when stopped the graphics display is redrawn using any new settings that might have changed but using the existing data buffers. The Exit button exits (kills) the program.

The menu section along the bottom contains the range ( V/Div ) and position controls for the Channel 1 and 2 voltage waveform displays. The entry labels are color coded to match the waveform trace colors. The V/Div spinboxs set the corresponding vertical ranges in the standard 1, 2, 5 step increments. Other values maybe entered manually. The position entry windows determine the vertical position of their scales with respect to the blue center line on the grid. That is to say the value entered corresponds to the number displayed next to the blue center line.

The graphics display area, show in figure 5, is where the various signal waveforms are plotted on either a black or white background depending on which is selected under the Options drop down. It consists of a main 10 by 10 grid with the center vertical and horizontal grid lines drawn in dark blue. Each major grid is sub divided into 5 sub grids by the short tick marks along the blue center lines. The horizontal grid lines are labeled with color coded text to match the corresponding waveform trace with the voltage scales on the left and Math scales on the right.

The red triangle, drawn on the left side in the example shown because the trigger input is set to C1-V indicates the trigger level.

Above the main grid area is a line of text showing the device ID, Sample rate and buffer size and if the acquisition loop is running or stopped. Below the main grid are three lines of text which display various information about the displayed plots. The first line shows the current time per division setting and the horizontal position of the left most grid line with respect to 0 time i.e. the trigger point.

The second and third lines of text are for displaying information related to Channel 1 and Channel 2 respectively. The selected V/Div is displayed along with any of the vertical measurements selected for that voltage channel.

While stopped (red Stop button clicked) if you left click anywhere within the display grid a numbered marker “x” point will appear at that position. In the upper left corner of the display grid the maker number along with the vertical ( voltage or current ) and horizontal ( time ) values will also appear. For marker points > 1 the vertical and horizontal delta to the previous point will also be displayed. Clicking the red Stop button again will clear the markers. Clicking on the green C1-V/Div, orange C2-V/Div buttons along the bottom of the main Time display window will select which vertical range / position axis will be used and the marker will be drawn in that color.

Under the Curves Drop down menu there are selectors for displaying the T cursor ( time ) and V cursor ( voltage ). When selected if you right click anywhere within the display grid either a vertical or horizontal cursor line, or both, will be drawn at that location. The vertical, horizontal, or both values for that point will be displayed. Scrolling with the mouse wheel will move the vertical line left–right when only the T cursor is selected and the horizontal line up-down when only the V cursor is selected. When both are selected the mouse wheel moves the vertical line left–right. With the Shift key pressed the mouse wheel will move the horizontal line up-down.

In addition to the pre-programed Math traces, ALICE Desktop provides a method of plotting user defined equations or formulas using the voltage waveform buffers for channels 1 and 2. The formulas are written in conventional Python syntax which is basically the same as you would expect to write any math expression. Any of the Python math ( and numpy ) module functions can be used such as www.cronistalascolonias.com.ar() or www.cronistalascolonias.com.ar() etc. Any of the ALICE global variables can be used but below is a list of the most useful available variables and constants:

Waveform Buffers:

VBuffA is the Channel 1 voltage sample array ( in volts )
VBuffB is the Channel 2 voltage sample array ( in volts )
VmemoryA is the Channel 1 voltage memory array used for Trace Averaging
VmemoryB is the Channel 2 voltage memory array used for Trace Averaging
AWGAwaveform is the AWG 1 waveform memory array
AWGBwaveform is the AWG 2 waveform memory array
t is the time index ( 10 uSec per point )
SAMPLErate is the sampling rate, which can be 1KSPS, 10KSPS, KSPS, 1MSPS, 10MSPS or MSPS

Vertical Position variables:

CHAOffset is the value in the channel 1 voltage position entry window
CHBOffset is the value in the channel 2 voltage position entry window

As a simple example, to plot the difference between the channel A and B voltage waveforms the following formula would be used:

(VBuffA[t] - VBuffB[t] - CHAOffset)

As the program iterates over the time index t, the channel 2 voltage value is subtracted from the channel 1 voltage value and then offset on the screen by the channel 1 position variable. This replicates the built-in math trace C1-V – C2-V.

A more advanced example calculates the time derivative of the channel 1 voltage waveform, or slew rate, and scales it to V/mSec:

(VBuffA[t] - VBuffA[t-1] ) *

Assuming a KSPS sample rate.

Again as the program iterates over the time index t, the channel 1 voltage value at t-1 is subtracted from the channel 1 voltage value at t and then multiplied by The scales the time from the 10 uSec per time sample to 1 mSec. The screen shot in figure 6, shows the result for a 4 V p-p triangle wave at 1 KHz. The green triangle wave changes 4 V in uS for a slew rate of + and – 8 V/mSec shown with the magenta Math trace.

A few words of caution, care must be taken when writing the formula to not cause a Python syntax error or other math exception such as divide by zero. If you make a mistake ALICE will stop and put up the math formula entry window so you can find and correct your mistake.

The AWG controls window is shown in figure 7.

There are two identical sets of controls for configuring the Channel 1 and 2 outputs. First there is a drop down menu for selecting the Mode, figure 8. The Hi-Z option disables the generator output (High Impedance mode). The default at start-up is that both channels are in Hi-Z mode.

The Min and Max entry windows program the minimum and maximum values for the output waveform. If the value entered in the Min window is higher ( more positive ) than the value entered in the Max window the apparent phase of the output wave is inverted. While this is somewhat redundant for the Sine, Triangle and Square wave shapes, given the Phase control described later, it is useful for determining if the Sawtooth or Stairstep shapes are rising or falling ramps.

The Freq entry window programs the frequency of the waveform in Hertz. Given the 75MSPS maximum AWG sample rate of the ALM, the maximum possible frequency is, by definition, MHz but the practical upper limit is more like 25 MHz or less.

The Shape drop down menu is used to select the shape of the output waveform. There are 6 built in waveform shapes, DC, Sine, Triangle, Sawtooth, Square, and a Stair Step. The number of steps can be set using the % entry slot, which changes label to Steps when in the Stair Step wave shape. When DC is selected the constant value of the output voltage is set by the value in the Max entry window.

The relative timing between the two AWG channels can be set as either a phase angle or delay in time. The Phase and Delay buttons choose between the two methods. The entry window programs either the phase of the output waveform in degrees from 0 to or the time delay in mSec. The % entry window applies to the Square, Trapazoid, SSQ and Up-Down Ramp shapes and programs the duty cycle or symetry in percent from 0% to %. For the Stairstep shape it set the number of steps.

Wave Shapes in the menu use the AWGAwaveform or AWGBwaveform array buffers to contain the waveform sample data points. A new data set based on the entered values is generated each time a shape button is clicked or a value is changed. The Impulse, Trapezoid, U-D Ramp, UU Noise ( uncorrelated uniform distribution ) and UG Noise (uncorrelated gaussian distribution ) buttons are used to build waveform arrays based on user input parameters.

The basic shape of the Impulse waveform is shown in figure The Max, Min, Freq, Phase and Duty-Cycle values are used to construct the waveform. The Freq setting determines the Period ( 1/Freq ) or spacing between the pulses. The output starts and ends at a value midway between the Min and Max values. The impulse consists of a positive peak followed by a negative peak. The width of the peaks are equal to (Period * DutyCycle)/ 2. The center of the pulse is delayed by the Phase setting. For example if the phase is set to then the pulse is delayed by ½ the Period (Phase/).

The Trapezoid waveform makes a pulse with a rise and fall time set by the number of mSec entered in the delay entry slot. The Min, Max, Freq, and Duty-cycle entries operate as in the Square Shape.

The U-D Ramp ( ramp up ramp down ) shape is much like the triangle shape except that the Duty-cycle entry sets the symmetry of the up and down ramps. For example if the Duty-cycle is set to 25% the wave will ramp up from Min to Max for 25% of the Period ( 1/Freq ) and then ramp down from Max to Min for 75% of the period.

The Fourier Series shape builds a waveform based on the Fourier series of cosines for a square wave. The number of odd harmonics of the fundamental is entered in the % entry slot, which changes label to Harmonics when in the Fourier wave shape. The minimum and maximum values of the fundamental are set using the Min and Max entries and the fundamental frequency is set using the Freq entry. Entering 1 for the number of harmonics will result in just the cosine wave at the fundamental frequency. Entering 3 for the number of harmonics will include the third harmonic, entering 5 for the number of harmonics will include the third and fifth harmonics and so forth. More information on this can be found in the Advanced Users Guide.

There are two Noise like waveforms that can be generated. A new data set is generated each time the button is clicked. That fixed data pattern is then send to the output each time sweep. UU Noise or uncorrelated uniform distribution is made using a random number with a uniform distribution between the Min and Max settings. The average value of the noise should be equal to Max+Min/2. UG Noise or uncorrelated Gaussian distribution is made using a random number with a Gaussian distribution centered on Max+Min/2 with a sigma of (Max-Min)/3.

Waveform data point values can be read in from a simple single column csv text file ( one row per time sample ) by clicking on the Read File button. For voltage waveforms the values can be decimal numbers ranging from -5 to +5 in volts. If the .csv file contains more than one column the user will be prompted to choose which column number to import. The user is also prompted to select a sample rate. The contents of the Min, Max, Freq, Phase and % entry slots are not used for wave shapes input from a file. Use the Custom Math Waveforms feature below to change the amplitude and offset of the waveform. The contents of the AWG 1 or AWG 2 waveform arrays can be saved to a csv file by clicking on the Save File button.

Waveform data point values can also be read in from an audio file in .wav format, 16 bit data. The sample rate is can be selected form the possible AWG sample rates. Mono files can be read into either the AWG 1 or AWG 2 waveform buffers. To read a stereo file use the Read WAV File button for AWG 1. The Left channel will be loaded into AWG 1 and the Right channel will be loaded into AWG 2. The 16 bit integer data is scaled and offset to fit within the -5 to +5 V range of the ALM Up to , sample points will be loaded. The open source audio program Audacity is a good option for generating and editing wave files.

A small library of example waveform files can be downloaded HERE.

In addition to the built-in AWG wave shapes, ALICE Desktop provides a method of generating user defined wave shapes from equations or formulas using the AWG waveform buffers for channels 1 and 2. The formulas are written in conventional Python syntax which is basically the same as you would expect to write any math expression. As with the Math plotting, any of the ALICE global variables can be used. Only difference is that the time increment variable (t) is not used. Care must be taken if the lengths of any arrays being used in the expression are of differing lengths. As a reminder the length of the waveform array(s) will be displayed below the % entry slot if the array for that AWG channel has been generated. The following example Python syntax allows setting the start and stop points to be used in the array:

AWGAwaveform[ start : stop ] where start and stop are integers.

For example to copy the CH 1 captured data from the VBuffA array to the AWGBwaveform array you would simply click on the Math option under the AWG 2 Shape menu and type VBuffA as the formula, as in figure

As a more complex example let’s say we want to add noise to a waveform that was read from a file. The first step is to read the data into the AWGAwaveform array. The waveform chosen for this example is samples long and is a full wave rectified sinewave that is 1 V p-p, from V to V. Then generate a noise waveform in the AWGBwaveform array by setting the AWG 2 Min and Max values to the desired amplitude of the noise ( + and - V in this example ) and the Freq ( ) such that the period of the noise will be as long as the waveform in AWG 1 ( length = points ).

Click on either UU Noise or UG noise. Now click on the Math shape button in AWG 2 and enter the following formula:

AWGAwaveform + AWGBwaveform +

The resulting output wave shapes are shown in figure The first screen shot is what the waveforms look like before they are summed and offset. The CH 1 trace in the second screen shot shows the shape as read in from the file and the CH 2 trace shows the calculated wave shape with the added noise and offset.

To demonstrate how to use the Oscilloscope Tool as a DC voltmeter consider the resistor voltage divider network, shown in figure E1. We wish to measure the voltages at the 4 nodes and the voltages across the 6 resistors. In the figure the nodes are numbered from N0 to N4 with N0 being the ground or common node that all the voltage measurements will be made with respect to. With the Oscilloscope Tool we can measure two node voltages at a time and the voltage difference between those two nodes. Open the Measurements Window and / or from the Meas C1 menu select from the –C1-V- section the Avg and C1-C2 check boxes. Likewise from the Meas C1 menu select from the –C1-V- section the Avg and C2-C1 check boxes.

We start with the network powered from the fixed +5 volt power supply at node N1 and the channel 1 input also connected to N1. The channel 2 input is connected to node N2. Click on the Run button and the N1, N2 node voltages will be displayed along with the difference between them as C1-C2 and C2-C1. We can now proceed around the network measuring pairs of nodes until we can fill out table 1 below. Figure E2 shows the voltmeter inputs connected to nodes N3 and N4. Any combination of two nodes can be measured and the voltage difference between the two nodes will be displayed.

Table 1 Node voltages

From the measured node voltages ( to measure the difference voltages the scope + and - inputs can be placed on the two nodes of interest ) we can get the voltages across the 6 resistors shown in table 2.

Table 2 Resistor voltages

From these voltages and the values of the resistors the currents through the resistors can be calculated.

When the X-Y Plot Window button is clicked in the Main Window the X-Y display Window should appear, as shown in figure It is sub divided into 3 sections.

The menu on the right allows selection of which of the four possible input channel waveform signals or Math formula is to be used for the X and Y axis. Given two possible signals, Channel 1 voltage Channel 2 voltage there are in theory 4 possible combinations for X and Y. Not all 4 have been implemented since, for example, plotting a signal vs itself such as C1-V vs C1-V is a rather meaningless straight line.

Under the -X Axis- heading there are two options to display the histogram of either the channel A voltage or the channel B voltage waveforms. The horizontal axis is in volts and controlled by either the CA or CB V/Div and V Pos controls. The vertical axis is the histogram count or number of hits at a given voltage level. The vertical axis scale is controlled by the MC1 or MC2 controls.

It is also possible to select Math on one or the other or both axis. If Math is selected for just one axis then the selected trace from the Math drop down menu is used. Only a few of the built-in Math traces are supported. If Math is selected for both axis then the entered X formula and Y formula, using the Enter X or Y Formula buttons, will be plotted. This allows greater flexibility in X-Y plotting at the expense of the typing in the function to be plotted. See the earlier section on how to enter Advanced Math Traces for the Oscilloscope display. The same applies here to the X and Y formulas.

Any one of the four vertical axis controls can be chosen for the X and Y axis using the Math X or Y Axis buttons. Generally when X-Y plotting using Math one or the other of the four channels are not being displayed and its axis controls will be available to be used.

The X-Cur and Y-Cur check boxes select vertical and horizontal cursor lines which operate much the same as the T and V cursors in the Time display grid.

There is also a check button to display the saved X-Y reference trace (see note above in Oscilloscope section on Snap-Shot option).

To demonstrate some of the features of the ALICE Oscilloscope and X-Y Plot Tools the following example circuit is offered. In figure E3 we see a simple NPN transistor ( 2N ) in the common emitter configuration with a KΩ resistor used to bias the base and a 1 KΩ resistor as the collector load. The collector load is supplied from the fixed +5 V power supply. We will use the ALICE software to plot I_B vs V_BE. Figure E3 also shows how we will connect the scope inputs to measure the V_CE (voltage at the collector with respect to ground) and I_C (voltage across the 1 KΩ resistor). We will also determine the value of the base drive signal, C1-V corresponding to I_C = 2 mA and then measure the input to output voltage gain around that operating point.

To plot V_BE and I_B we first start out with the channel 1 input (C1-V) connected across the KΩ base resistor. As the formula in figure E3 states, I_B can be calculated by taking the differential voltage C1-V and dividing by the KΩ resistor value. KΩ is chosen to simplify the calculations so that the current is found by just moving the decimal point of the measured voltage ( i.e. 1 V = 10 uA ). The V_BE is measured with scope input for C2 connected to the base and the emitter (ground).

Set up the AWGs as follows: AWG 1, Mode set to Enab, Shape set to Triangle, Min set to , Max set to , Freq set to AWG 2 is not being used so the Mode can be set to Hi-Z.

The time base should be set to mSec/Div so that one full cycle from 0 to volts will fill the grid. Set the Trigger level so the start of the cycle will be displayed. Under the Curves menu select C1-V and C2-V.

Press the green Run button. You should see something like figure E4.

The green C1-V trace is the voltage across the KΩ resistor and represents I_B as 10 uA/V. The orange C1-V trace is the voltage on the base of the transistor or V_BE.

Pause or Stop the program ( red Stop button )

To make an XY plot of I_B vs V_BE open the X-Y Plot Window with the X-Y Plot Enab box checked. In the X-Y Display window press the C2-V button in the -X Axis- section and the C1-V button in the -Y Axis- section. In the X-Y Window set the C1 V Pos entry to and the C1 V/Div to and the C2 V Pos entry to and the C2 V/Div to

Press the green Run button. You should see something like figure E5.

The base current is very small when V_BE is less than V so there is likely to be noise in that part of the trace. Remember that the vertical voltage scale ( V/Div ) is divided by the KΩ resistor so it is 5 uA per division.

To plot the collector current I_C move the Channel 2 + input to the +5V power supply and the channel 2 - input to the collector of the transistor. Now we need to go back to the time display window. Uncheck the X-Y Plot box and make sure the Time Plot box is checked.

Press the green Run button. You should see something like figure E6.

I_C should be nearly zero where C1-V is less than V. You may need to tweak the Offset factor to get I_C to be exactly on the grid line. An easy way to check this is to temporarily move the channel 2 - input to the +5 V power supply. Now the differential input to scope channel C2-V is exactly zero.

Remember that the vertical voltage scale ( V/Div ) is divided by the 1 KΩ resistor so it is mA per division. With the program paused, under the Options menu press the SnapShot button. This saves a copy of the displayed C1-V and C2-V traces. Under the Curves menus select R2-V. This will now display the saved I_C plot.

To plot the V_{CE</sub >move the Channel 2 + input to the collector of the transistor and the channel 2 - input to ground. Press the green Run button. You should see something like figure E7.}

Now move the channel 2 + input back to the base of the transistor. Press the green Run button. You should see something like figure E8.

Now we have plots of I<sub>C ( dark orange ), I_B ( green ) and V_BE ( orange ) on the same grid as the base resistor bias from AWG 1 is swept from 0 to 5 V.

Under the Curves Menu select the V cursor. Right click on the time grid where the dark orange I_C trace crosses the 2 V grid ( or 2 mA ). The voltage value at that point will appear next to the horizontal cursor line. The Use the mouse wheel it adjust the cursor up or down so it lines up exactly where the I_C curve cross the time grid line. It should look like figure E9.

The beta of the transistor can now be calculated by scrolling the cursor down till it lines up exactly where base current (magenta trace) at the same time grid line. The displayed voltage will represent the base current. Beta will be I_C / I_B. For this example I_B is about 12 uA so beta will be around

The AWG 1 value where the green trace crosses the same Time Grid as I_C = 2 mA should correspond to the base bias point where I_C is equal to 2 mA. This is the bias point we would like to center our input signal on for the next measurement of the amplifier gain.

Move the scope channel 1 + input back to the AWG 1 output, - input to ground and the scope channel 2 + input back to the collector of the transistor, - input to ground.

Calculate new Min and Max values for AWG 1 by adding and subtracting V to the 2 mA bias point we just measured. Enter these for AWG 1. Set AWG 1 mode to sine wave. Under the Curves menu turn off the R2-V trace and under the Math menu select none. Set the time base to mS/Div so that two cycles of the input waveform are displayed. Under the Meas C1 and C2 menus in the -C1 V- and -C2 V- sections select Avg and P-P to be displayed.

Press the green Run button. You should see something like figure E

The DC average of the output waveform should be at about 2 V ( 2 mA in the collector load resistor ) below the +5 V power supply or about +3 V. The voltage gain of the amplifier will be the Channel 2 P-P value divided by the Channel 1 P-P value. Which for this example is about

When the Spectrum window button is clicked in the Main Window the Spectrum display Window should appear, as shown in figure It is sub divided into 2 sections.