This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
university:tools:m1k:alice:oscilloscope-x-y-user-guide [27 Jan 2021 22:37] – use wp> interwiki links Robin Getz | university:tools:m1k:alice:oscilloscope-x-y-user-guide [17 Jan 2023 20:03] (current) – add cautionary note Doug Mercer | ||
---|---|---|---|
Line 12: | Line 12: | ||
<WRAP centeralign> | <WRAP centeralign> | ||
+ | |||
+ | ====The Top Menu Section==== | ||
+ | |||
+ | The menu section along the top, shown in figure 1T, 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. | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | ===Triggering functions=== | ||
+ | |||
+ | The ADALM1000 signal generation and measurement hardware is tightly integrated and can operate in two modes. As an integrated Source/ | ||
+ | |||
+ | The Trigger button is a drop down menu listing which signal to trigger on, CA-V, CA-I, CB-V, CB-I or none. The use of Triggering to display a stable trace is generally necessary when viewing externally generated signals. When viewings internally generated signals from one or the other of the AWG channels a stable trace happens automatically when the AWG Sync function is enabled i.e. the beginning of the AWG output waveform is restarted at the same point at the start of each time sweep. | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | 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 Low Pass Filter option applies a variable length digital low pass filter function to the selected waveform before searching for the trigger condition. This can be used to filter high frequency noise that might be on the signal of interest and better stabilize the triggering. The length of the filter, in samples, can be set/ | ||
+ | |||
+ | When Manual Triggering is selected one sweep is acquired and displayed each time the green Run button is clicked. | ||
+ | |||
+ | When Single Shot Triggering is selected triggering is " | ||
+ | |||
+ | 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 CA-V and CB-V or mA for CA-I and CB-I. | ||
+ | |||
+ | The 50% button sets the trigger level to the midpoint (50% point) of the selected trigger waveform. i.e. to the (maximum + minimum)/2. | ||
+ | |||
+ | ===Horizontal Time Controls=== | ||
+ | |||
+ | < | ||
+ | |||
+ | There are two sweeping modes in the time domain display. The conventional time per Div based view and a rolling mode. The Roll Mode in a digital storage oscilloscope uses a display different from that of the usual time-based view. While viewing a very low-frequency periodic signal in the usual time per Div based view the screen up dates, is redrawn, with the next new trace only after a screen’s worth of data samples are captured. This can take a few seconds for 100 mS/Div or greater time bases. Rather, in Roll Mode the trace is redrawn continuously and moves from right to left along the time-axis as new samples are taken, resembling what you would see in an analog strip chart. The time axis, rather than starting at the triggering point as in conventional mode, remains static and the waveform moves or rolls. Accordingly, | ||
+ | |||
+ | 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. This is mainly used when synced to the AWG. Due to the discontinuous nature of the AWG outputs this allows the user to skip over any initial transients that might appear if the system being measured has " | ||
+ | |||
+ | 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. | ||
+ | |||
+ | ===Trace Controls=== | ||
+ | |||
+ | The Curves drop down menu button allows the selection of which signal waveform traces will be displayed vs time. The All button selects all four curves to be displayed and the None button clears all four curves. Plot the Math-X and Math-Y formulas by clicking on those options. ALICE can automatically adjust the trace vertical position to center the CA-V and /or CB-V traces on the midpoint of the waveform each sweep by clicking on either or both of the options below the –Auto Vert Center- heading. This is analogous to a software " | ||
+ | |||
+ | When using external Resistor Divider attenuators the frequency response of the Channel may be reduced. The software High Pass frequency compensation can be selected for either channel by clicking on the buttons below the –Input HP Comp- heading. See the section on Analog Inputs below | ||
+ | |||
+ | It is also possible to select which of the possible stored reference time traces, if saved via the Snap-Shot option, will be displayed. | ||
+ | |||
+ | At the bottom are options to enable the vertical Time and horizontal Voltage (Current) cursors. | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | The green PWR-On button toggles on and off the fixed analog +2.5 V and +5 V power supplies. The button turns red when the supplies are off. The power supplies do not turn completely off but go to around +2 V and can supply only about 20 mA when shorted to ground. This is much less than the 200 mA or so they could supply if accidentally shorted when on. 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. | ||
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 CA-V and CB-V traces. | 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 CA-V and CB-V traces. | ||
+ | |||
+ | ===ALICE Scope/AWG only option=== | ||
By setting to 1 the EnableScopeOnly = 1; option in the alice_init.ini file, the Oscilloscope and AWG controls can be combined in one window as shown in figure 1S. The controls all work as they do in the default two window configuration (See [[university: | By setting to 1 the EnableScopeOnly = 1; option in the alice_init.ini file, the Oscilloscope and AWG controls can be combined in one window as shown in figure 1S. The controls all work as they do in the default two window configuration (See [[university: | ||
Line 37: | Line 99: | ||
Press the <alt> and < | Press the <alt> and < | ||
- | 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 A and B voltage and current 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 2,000 samples and a maximum of 90,000. 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, | + | 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 (with Save To CSV button) | ||
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 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. | ||
Line 45: | Line 109: | ||
<WRAP centeralign> | <WRAP centeralign> | ||
- | 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 Trace Avg button turns on trace averaging. The number of sweeps to average can be set from the Change Settings controls |
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 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. | ||
Line 192: | Line 256: | ||
To keep production costs of the board low, certain trade offs were made. One was to forego programmable input gain ranges that use resistor dividers and perhaps adjustable frequency compensation capacitors. This limited the usable input voltage range to 0 to +5V. | To keep production costs of the board low, certain trade offs were made. One was to forego programmable input gain ranges that use resistor dividers and perhaps adjustable frequency compensation capacitors. This limited the usable input voltage range to 0 to +5V. | ||
- | 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 A and B inputs ( possibly used when in the high impedance or Split I/O modes ). Save and Load Adj buttons can be found under the File drop down menu. | + | 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 A and B inputs ( possibly used when in the high impedance or Split I/O modes ). Save and Load Adj buttons can be found under the File drop down menu. |
- | The input capacitance, | + | ===Input Divider Calculator=== |
- | A capacitor would generally be needed across the input resistor R< | + | To make calculating an input resistor divider' |
+ | |||
+ | {{ : | ||
+ | |||
+ | <WRAP centeralign> | ||
+ | |||
+ | Values for resistor R1 and resistor R2 are entered as well as any offset voltage that is applied to the bottom of the divider. The Exact values, as measured with a bench DMM, can be entered for R1 and R2 to calculate more accurate gain and offset results. The Rint internal 1 MegΩ resistance of the channels is taken into account in the calculation as this will have a significant effect for higher values of R1 and R2. Click the Calculate button to calculate the values. The Channel A or B entries can then be set to the calculated values using the Set CH A and Set CH B buttons respectively. These values can then of course be tweaked as needed for even better accuracy. | ||
+ | |||
+ | === Software Frequency Compensation=== | ||
+ | |||
+ | The input capacitance, | ||
+ | |||
+ | < | ||
+ | |||
+ | To give you a rough idea let's use 400 pF for C< | ||
{{ : | {{ : | ||
Line 205: | Line 283: | ||
The software frequency compensation for each channel consists of a cascade of two adjustable | The software frequency compensation for each channel consists of a cascade of two adjustable | ||
+ | |||
+ | <note tip> | ||
+ | **Exponential compensation**\\ | ||
+ | An Exponential compensation technique adds one or more exponentially decaying terms to a step in the signal. With 2 available stages, ALICE can correct for multiple spurious inductances and capacitances in the input divider circuit. Exponential compensation works best for overshoots and undershoots smaller than about 10% of the step height. In this case, a sum of exponential terms is an accurate generic model for such defects. | ||
+ | </ | ||
In figure In2 we show the new controls for the input compensation. To turn on and off the compensation for Channels A and B check boxes are added under the Curves drop down menu. Turning on compensation applies to both the Scope and Spectrum tools (time and frequency measurements). The filter time constant and gain settings can be set using new entry slots in the Settings Controls screen. The DC gain and offset adjust controls are unchanged. | In figure In2 we show the new controls for the input compensation. To turn on and off the compensation for Channels A and B check boxes are added under the Curves drop down menu. Turning on compensation applies to both the Scope and Spectrum tools (time and frequency measurements). The filter time constant and gain settings can be set using new entry slots in the Settings Controls screen. The DC gain and offset adjust controls are unchanged. | ||
Line 232: | Line 315: | ||
As we can see for this example the DC gain setting is slightly more than 2 which is to be expected based on the internal 1 MΩ resistor and external 1 MΩ R< | As we can see for this example the DC gain setting is slightly more than 2 which is to be expected based on the internal 1 MΩ resistor and external 1 MΩ R< | ||
- | The input gain factor of 2 (2.17 to be exact) increases the allowable measurement range from 0 to +5 V to about 0 to +10 V. Enough to work with circuits powered from a 9 V battery. If you have a 9 V battery try measuring it by connecting the - battery terminal to GND and the + battery terminal to the end of the 1 Meg resistor. You should read about +9 V for the DC average. | + | The input gain factor of 2 (2.17 to be exact) increases the allowable measurement range from 0 to +5 V to about 0 to +10 V. Enough to work with circuits powered from a 9 V battery. If you have a 9 V battery try measuring it by connecting the - battery terminal to GND and the + battery terminal to the end of the 1 Meg resistor. You should read about +9 V for the DC average. |
===Adjusting the compensation filter=== | ===Adjusting the compensation filter=== | ||
Line 250: | Line 333: | ||
[[university: | [[university: | ||
[[university: | [[university: | ||
- | |||
- | ====The Top Menu Section==== | ||
- | |||
- | 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. | ||
- | |||
- | ===Triggering functions=== | ||
- | |||
- | The ADALM1000 signal generation and measurement hardware is tightly integrated and can operate in two modes. As an integrated Source/ | ||
- | |||
- | The Trigger button is a drop down menu listing which signal to trigger on, CA-V, CA-I, CB-V, CB-I or none. The use of Triggering to display a stable trace is generally necessary when viewing externally generated signals. When viewings internally generated signals from one or the other of the AWG channels a stable trace happens automatically when the AWG Sync function is enabled i.e. the beginning of the AWG output waveform is restarted at the same point at the start of each time sweep. | ||
- | |||
- | {{ : | ||
- | |||
- | <WRAP centeralign> | ||
- | |||
- | 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 Low Pass Filter option applies a variable length digital low pass filter function to the selected waveform before searching for the trigger condition. This can be used to filter high frequency noise that might be on the signal of interest and better stabilize the triggering. The length of the filter, in samples, can be set/ | ||
- | |||
- | When Manual Triggering is selected one sweep is acquired and displayed each time the green Run button is clicked. | ||
- | |||
- | When Single Shot Triggering is selected triggering is " | ||
- | |||
- | 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 CA-V and CB-V or mA for CA-I and CB-I. | ||
- | |||
- | The 50% button sets the trigger level to the midpoint (50% point) of the selected trigger waveform. i.e. to the (maximum + minimum)/2. | ||
- | |||
- | ===Horizontal Time Controls=== | ||
- | |||
- | 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. This is mainly used when synced to the AWG. Due to the discontinuous nature of the AWG outputs this allows the user to skip over any initial transients that might appear if the system being measured has " | ||
- | |||
- | 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. | ||
- | |||
- | ===Trace Controls=== | ||
- | |||
- | The Curves button allows the selection of which signal waveforms will be displayed when plotting vs time. The All button selects all four curves to be displayed and the None button clears all four curves. 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 green PWR-On button toggles on and off the fixed analog +2.5 V and +5 V power supplies. The button turns red when the supplies are off. The power supplies do not turn completely off but go to around +2 V and can supply only about 20 mA when shorted to ground. This is much less than the 200 mA or so they could supply if accidentally shorted when on. 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 Bottom Menu Section==== | ====The Bottom Menu Section==== | ||
Line 525: | Line 566: | ||
=====Applying Digital Filtering: | =====Applying Digital Filtering: | ||
- | With this interface, ALICE Desktop can apply digital filtering to the captured Channel A and B voltage waveform data before being displayed in the Time and/or Frequency domains. ALICE uses the numpy convolve function to perform the filtering function. It is possible to have the program generate a simple Box Car (moving average) filter by setting the length and then clicking on the Box Car check box. | + | With this interface, ALICE Desktop can apply digital filtering to the captured Channel A and B voltage waveform data before being displayed in the Time and/or Frequency domains. Digital filtering can also be applied to the contents of the generated AWG waveform buffers as well. ALICE uses the numpy convolve function to perform the filtering function. It is possible to have the program generate a simple Box Car (moving average) filter by setting the length and then clicking on the Box Car check box. |
The supplied list of coefficients is convolved with the captured data buffer. The list of filer coefficients for either Channel A or B is first loaded from a single column .csv file by using the “Load CH A Filter Coef” and “Load CH B Filter Coef” buttons. The length ( number of coefficients ) and file name will then be displayed. The digital filter(s) will be applied to the voltage waveform data buffers if the “Filter CH A” and/or “Filter CH B” checkboxes are checked. | The supplied list of coefficients is convolved with the captured data buffer. The list of filer coefficients for either Channel A or B is first loaded from a single column .csv file by using the “Load CH A Filter Coef” and “Load CH B Filter Coef” buttons. The length ( number of coefficients ) and file name will then be displayed. The digital filter(s) will be applied to the voltage waveform data buffers if the “Filter CH A” and/or “Filter CH B” checkboxes are checked. | ||
Line 537: | Line 578: | ||
Alternatively, | Alternatively, | ||
- | The DFiltACoef and DFiltBCoef array variable are used to store the filter coefficients. The Filter formula coefficient scaling feature can be used to scale a set of filter values read from a file. First read in the values from the file and then simply pass the array through the formula function by entering DFiltACoef or DFiltBCoef for the formula. | + | The DFiltACoef and DFiltBCoef |
There are many filter design tools that can be found by searching the web. Here is one that works well but we are not necessarily endorsing it over any others that might be out there: | There are many filter design tools that can be found by searching the web. Here is one that works well but we are not necessarily endorsing it over any others that might be out there: | ||
- | http:// | + | [[http:// |
The array of coefficients ( filter taps ) that it generates as part of the C source code can be copy and pasted into a .csv file for use in ALICE. | The array of coefficients ( filter taps ) that it generates as part of the C source code can be copy and pasted into a .csv file for use in ALICE. |