Contents
Oscilloscope 2.51 Help Contents

Thank you for using Oscilloscope for Windows version 2.51, a tool that adds new power to your PC's sound hardware. This help file covers the following topics:

Overview

Precautions

System requirements

Starting Oscilloscope

Front panel controls

Menu controls

Usage tips

New features in ver. 2.51

Copyright

Oscilloscope for Windows is free for personal use and is supplied to you on an "as is" basis.

Tech support requests, suggestions, and bug reports can be e-mailed to the author at zeld@polly.phys.msu.su.

Any feedback concerning Your use of the Oscilloscope and the tasks you could accomplish with it will be very much appreciated.


General information about Oscilloscope

Oscilloscope for Windows95 version 2.51 (Oscilloscope 2.51) is an application showing how home PC peripherials, such as a sound card, can be used in an unconventional way, emulating industrial ADC hardware. The Oscilloscope provides a complete functionality of a "standalone" scope in a familiar Windows ennvironment.

The Oscilloscope allows you, for example:

- to study in real time any signal envelope,

- to measure frequencies,

- to study realtime signal spectra,

- to plot Lissajous patterns.

- to measure a cross-correlation coefficient of two signals

  (In general, to do most things you can do with an oscilloscope and a spectrum analyzer).

Not surprisingly, the Oscilloscope has several drawbacks too:

- non-calibrated amplitude level (hard to use as digital multimeter),

- relatively low bandwidth (20 Hz - 20 kHz),

- possibility of damage of a PC when connecting to an unknown signal source.  (See Precautions ).

Specifications:

Dual trace digital storage oscilloscope with realtime spectrum analyzer and correlometer.

Buffer length: 52 ms

Bandwidth: 20 Hz - 20 kHz max

Input level: about 2 VAC, limited by sound card capabilities

Display refresh: ca. 6 fps

Data export: disk file or Windows clipboard, text format


Starting Oscilloscope

 To start Oscilloscope, simply click ON LINE button and feed some wave to your sound card, for example speak in the microphone. If no wave is seen, check your audio mixer settings: signal source must be either Microphone or Mixer, and gain level must be set not too low. You can also check the switch on the microphone itself, and drag Y1 and Y2 sliders to their average positions.

To hold the wave, click HOLD button.


Safety measures when using Oscilloscope

 Being a software, Oscilloscope itself cannot damage your hardware, but it is very easy to burn out at least your sound card when trying to investigate some signal with unknown amplitude and DC offset.

 So, you must always be extremely careful when establishing an electrical connection between your computer and external equipment. It may be a good practice to use first a conventional multimeter or oscilloscope to find out whether signal levels are acceptable for your sound card.

 It is safe to connect to any audio/video equipment using standard line-in jacks and cables. You may consider using an old tape recorder, amplifier or turntable as a buffer device between your sound card and non-standard signal source. This can save your computer in case of a poorly grounded, unstable singal source, as well as allow you to control signal level manually before it reaches the sound card.

To avoid personal injury, always follow the usual safety rules when working with electric circuits.

OSCILLOSCOPE IS SUPPLIED TO YOU AS IS, AND IN NO CASE THE AUTHOR OF OSCILLOSCOPE IS RESPONSIBLE FOR PERSONAL INJURY, HARDWARE AND/OR DATA DAMAGE, PROPERTY DAMAGE OR PROFIT LOSS ARISING FROM USE OR INABILITY TO USE THE OSCILLOSCOPE.

THE AUTHOR DOES NOT GUARANTEE THE FITNESS OF OSCILLOSCOPE FOR ANY PARTICULAR PURPOSE. OSCILLOSCOPE IS NOT INTENDED FOR INDUSTRIAL OR COMMERCIAL USE.

IN GENERAL, USE OSCILLOSCOPE AT YOUR OWN RISK.

ALWAYS CONSULT YOUR SOUND CARD MANUAL FOR DETAILS ON CONNECTING TO EXTERNAL DEVICES.


Plotting Lissajous patterns

Oscilloscope allows you to plot both genuine Lissajous patterns, when y-coordinate of the ray is proportional to the level in one channel,  and x-coordinate is taken from the other, and pseudo-Lissajous figures,  when x is the time-delayed y.

  To plot Lissajous patterns, feed proper signals to the sound card,  and activate XY plot mode ( O button on the toolbar).  Y1 channel is then mapped to vertical deflection, and Y2 to horizontal one.  In this mode, Y1 and Y2 sliders control  vertical and horizontal coordinate gain, T controls the duration of  signal plotted, and Delay sliders allow you to change time delay between  Y1 and Y2 channels. Pos Y1 and Pos Y2 sliders move the plot around the screen  in up-down and left-right directions.

  Pseudo-Lissajous patterns do not require two different signals input to  the sound card, and you can use a simple mono microphone, for example.   Delay sliders are the most important controls then, as they change time delay between x and y signals.

Technically, pseudo-Lissajous patterns are is based on the fact that monophonic signal sources feed an identical signal both in left and right channels (Y1 and Y2). There is no difference in Oscilloscope's work when plotting genuine or pseudo Lissajous patterns.


Oscilloscope front panel controls

Oscilloscope for Windows is controlled in the same way as most conventional oscilloscopes.

Click on the controls to see their purpose.

See also:

Oscilloscope menu controls


Display Mode function
Display Mode switch

Display Mode switch controls what traces will be plotted on the screen:

Waveform mode

Mode	Trace(s) plotted
YT Single Trace	Y1 vs. time
YT Dual Trace	Y1 vs time, Y2 vs. time
XY Plot	Y1 vs. Y2  (Y2 used as X deflection)

FFT mode

Mode	Trace(s) plotted
YT Single Trace	Amplitude vs. frequency
YT Dual Trace	Amplitude vs. frequency, phase vs. frequency
XY Plot	Amplitude vs. frequency

Oscilloscope records the signal from Y2 channel independently of Y2 switch setting: you can observe some wave in YT Single Trace mode, press HOLD, and then examine both channels by using the Display mode switch.


Y2=Y1 switch function
Y2=Y1 switch

This switch locks Y1 and Y2 gain sliders together, so software gain is identical in both channels and can be changed simultaneously by dragging either of Y1 and Y2 sliders. When turning Y2=Y1 on, Y1 and Y2 values are averaged if Y1 and Y2 gains are not equal. If Display Mode switch is set to XY Plot, Y and X gains are set equal.


ms/div switch function
ms/div switch

ms/div switch selects timebase band. If set to 5 ms/div, T slider performs continuous timebase tuning in the range of  5 ms to 50 ms (full sweep). The other band is 0.5 ms/div ( 0.5ms to 5 ms full sweep).


Line button function
On Line button

Clicking the On Line button switches Oscilloscope to ON LINE mode. Sound card ADC is activated, and the realtime waveform is displayed.

See also:HOLD


Store button function
Store button (S)

Clicking the Store button turns storage mode on. In this mode, Oscilloscope works like a storage oscilloscope, when every trace plotted remains on the screen. Storage mode can be used either in ON LINE or HOLD modes. To clear the screen, click the Store button once more.

 In storage mode you can not, however, recall the waveform recorded previously and record it in the file, because only the display picture is stored and not the raw data. This allows to use storage mode for any desired period of time without worrying of overflow errors.


Analog-to-Digital Converter


Hold button function
Hold button

Clicking the Hold button switches Oscilloscope to HOLD mode. In this mode, the last recorded waveform is displayed, and every front panel control of Oscilloscope remains enabled. This allows you to examine the waveform more carefully than in flickering and sometimes not responsive ON LINE mode.

See also:LINE


Check button function
Check (1:1) button

Clicking the Check button temporarily sets software gain of both channels to 1, and offsets to 0, i.e. one ADC level unit is one pixel height, and zero level is at middle horizontal graticule line. This is useful to check the level fed to your sound card: if the waveform exceeds graticule limits, it may be distorted because the ADC produces levels from -128 to 127, and these extreme values are used whenever the signal level should be greater. So, if sine wave 'bumps' are flat, consider decreasing hardware gain using your audio mixer software (or some physical level knob).

 In ON LINE mode, Check mode is enabled while Check button is pressed; in HOLD mode, clicking Check button toggles Check mode on and off as indicated in the status stirng on Oscilloscope display.


Meter button function
Meter button

 Clicking the Meter button toggles Meter mode on and off. In Meter mode, you can measure time and level of a waveform simply by clicking left and right mouse buttons on the Oscilloscope display.

Left button click sets cursor 1 and right click sets cursor 2. When both cursors are set, the difference between the cursors’ positions is shown in the right three parts of the status bar.

For convenience, the reciprocal value of time/frequency difference is shown in the 1/dt (1/dF) status window. This allows, for example, to quickly measure the frequency of a wave by clicking left and right buttons on the successive maximums and looking at 1/dt value.

Note: ADC levels are integer; the decimal parts you see are interpolated values.


Position Y1 slider
Pos Y1

 “Pos Y1” slider controls Y1 channel DC offset, i.e. shifts the entire Y1 trace up and down. If the display mode is XY plot, this slider shifts the whole plot up and down.

Note: “Pos Y1” slider has no effect while in Check (1:1) mode. Check mode sets DC offsets to zero.


Position Y2 slider
Pos Y2

 “Pos Y2” slider controls Y2 channel DC offset, i.e. shifts the entire Y2 trace up and down. If the display mode is XY plot, this slider shifts the whole plot left and right.

Note: “Pos Y2” slider has no effect while in Check (1:1) mode. Check mode sets DC offsets to zero.


Y1 slider function
Y1 slider

Y1 slider controls software gain of Y1 (left stereo) channel, i.e.Y1 trace amplitude or Lissajous pattern height.Use your audio mixer software to adjust hardware gain. The current software gain level is indicated in Gain status windows on the Oscilloscope control panel.

In FFT mode, the gain in Y1 (amplitude) channel is proportional to the product of the levels of Y1 and Y2 slider. This creates a convenient faster-than-linear response.

Note: when check mode is on (1:1 button is pressed), the software gain is set to 1, irrespective to Y1 slider setting. “Pos Y1” control also has no effect while in check mode.


Y2 slider function
Y2 slider

Y2 slider controls software gain of Y2 (right stereo) channel, i.e.Y2 trace amplitude or Lissajous pattern width.Use your audio mixer software to adjust hardware gain. The current software gain level is indicated in Gain status windows on the Oscilloscope control panel.

In FFT mode, the gain in Y1 (amplitude) channel is proportional to the product of the levels of Y1 and Y2 slider. This creates a convenient faster-than-linear response. The gain in Y2 (phase) channel is proportional to the level of Y2 slider.

Note: when check mode is on (1:1 button is pressed), the software gain is set to 1, irrespective to Y2 slider setting. “Pos Y2” control  also has no effect while in check mode.


T slider function
T slider

T slider controls timebase duration (time scale), i.e. stretches or shrinks the waveform displayed. This is a log-scale slider. Timebase bands are switched using  “5ms/div” and “0.5 ms/div” buttons on the toolbar. In FFT mode, the T slider controls the frequency scale. The current time (or frequency range) of a full-screen sweep is displayed in the Sweep status window on the Oscilloscope control panel.


Delay sliders function
Delay sliders

The two delay sliders (coarse and fine) control  triggering delay in YT Single Trace Mode or time delay between Y1 and Y2 channels displayed in YT Dual Trace or  XY Plot mode. The coarse delay slider controls delay in the range of ±45ms, and the fine delay slider has the range of ±5ms. The total time delay is the sum of coarse and fine delay sliders values. The values of both sliders and the total delay are shown in Delay status windows on the Oscilloscope control panel.

In YT Single Trace mode, delay sliders can be set to obtain a pretrigger view.

In FFT mode time delay sliders have no effect.


Trg  Lev slider function
Trigger Level slider

Trg Lev slider controls triggering level. If Trigger switch is not OFF, time sweep begins at the moment when the absolute value of Y1 signal level exceeds the level set by Trg Lev slider,  the signal is positive (negative) depending on the Trigger switch, and the signal raises (for positive trigger level) or falls (for negative level). The current triggering level is shown as a green dash at the left edge of Oscilloscope display.


Trigger switch function
Trigger switch

Trigger switch are the three trigger buttons on the toolbar :

OFF        : do not use triggering, display unsynchronized signal.

Positive   : Trigger time sweep by positive signal level.

Negative  : Trigger time sweep by negative signal level.

See also:

Trg Lev slider


Correlometer

 The Correlometer displays correlation coefficient between Y1 and Y2 channels.

 Correlation coefficient R is given by

R = <  Y1 * Y2  > / (rms_Y1 * rms_Y2).

Before the calculation of R, DC level is subtracted from both signals; averaging is always performed over the whole ~52 ms buffer.

Left from the correlation coefficient (R) bar, signal levels in Y1 (left) and Y2 (right) channels are displayed. Signal level is defined as sqrt(2) times its rms level, which gives the peak amplitude for the sine wave. Thus, if sine wave is displayed, Correlometer is on, and Check mode is on, the amplitude of the wave must be the same as the height of level bar for the appropriate channel.

 Colors for the R bar (either positive and negative) and level bars can be adjusted using Setup|Colors menu.


Reset Controls button
Reset Controls

The Reset Controls button sets all the sliders on the control panel to their default positions.


Oscilloscope Menu Controls

Oscilloscope menu controls are used for data manipulation, customizing Oscilloscope, and obtaining help.

Main menu items are:

File    Edit    Setup     Help


Edit menu

The Edit menu allows you to copy the current waveform to Windows Clipboard. The data are copied as text file, and then can be pasted into a variety of applications, including Microsoft Excel and Microcal Origin.

The various options for the data output are common for both clipboard and disk file output and are controlled by Setup/Data file... dialog panel. However, unlike disk file output, copying data to the clipboard can be  performed in ON LINE mode, without pressing the HOLD button.

Either the waveform or spectrum data can be copied; note that the spectrum data being copied is controlled by Setup/Data file... dialog panel, and in some cases can not match the plots displayed.


File menu

The File menu contains commands for saving the current waveform  into a disk file and quitting Oscilloscope. Certain data file format options can be set using the Setup|Data file... dialog panel.


Setup menu

The Setup menu commands control data output formats (Data file), ADC options (Timing), and Oscilloscope display colors (Colors). All the settings can be made permanent using Save setup command. The active configuration file is winscope.ini in the Windows directory.


Usage tips
Oscilloscope usage tips

Connecting two microphones to your computer

If you have a true stereo sound card, capable of recording two signals at a time (and not duplicating the same waveform to both channels), you may find helpful to use a Book-on-tape audio adapter (Radio Shack P/N 274-396). This adapter has two jacks (left and right) connected to the appropriate contacts of a stereo plug. This is very convenient when you connect two microphones to the stereo card. However connecting two devices to sound card's Line-in jack is potentially dangerous due to the possible improper grounding. (The ground wires are connected together in the adapter).

Getting the fastest Oscilloscope refresh

Use 11 kHz sampling, 25 ms refresh, check Disable Warning and set YT Single Trace mode.


Copyright
COPYRIGHT NOTICE

Oscilloscope for Windows95, version 2.51.

Copyright (C) Konstantin Zeldovich, 1996-1997.

This software is free for personal use and can be redistributed provided it is not altered in any way and no fee is requested.

Terms for including this software into any software packages are available from the author.

Suggestions, questions, and bug reports should be addressed to Konstantin Zeldovich at  zeld@polly.phys.msu.su  .

OSCILLOSCOPE IS SUPPLIED TO YOU AS IS, AND IN NO CASE THE AUTHOR OF OSCILLOSCOPE IS RESPONSIBLE FOR PERSONAL INJURY, HARDWARE AND/OR DATA DAMAGE, PROPERTY DAMAGE OR PROFIT LOSS ARISING FROM USE OR INABILITY TO USE THE OSCILLOSCOPE.

THE AUTHOR DOES NOT GUARANTEE THE FITNESS OF OSCILLOSCOPE FOR ANY PARTICULAR PURPOSE. OSCILLOSCOPE IS NOT INTENDED FOR INDUSTRIAL OR COMMERCIAL USE.


Timing dialog panel

The Timing dialog panel controls ADC and Oscilloscope timer options.

You can select the ADC sampling frequency, Oscilloscope display refresh period,and toggle the "TIMEOUT" warning message.

The sampling frequency is the rate at which the input waveform is measured and digitized. The higher is the sampling frequency, the closer is the digital representation of the signal to its original form. However, higher sampling frequency requires much more data to be processed before displaying, and can slow the display refresh rate (or result in "TIMEOUT" warning). The available sampling frequencies are from 11 to 44 kHz and are determined by the sound card circuitry. Usually, 22 kHz is a reasonable compromise between fidelity and  display smoothness.

The Refresh input box allows you to select the Oscilloscope internal timer period. If Disable Warning checkbox in not checked, and no TIMEOUT warning blinks in the lower right corner of Oscilloscope display, Oscilloscope is displaying TWO different frames every x milliseconds, where x is the value you specify in the Refresh input box. Limits are 25 < x < 65535, but any value of x > 1000 is impractical because of very slow blinking display.

If the Disable Warning checkbox is checked, the TIMEOUT warning does not appear on Oscilloscope display even if there are certain Oscilloscope internal timing discrepancies normally leading to this message. This is for your convenience only and has no other effect on Oscilloscope work. Note that TIMEOUT warning is not a sign of an abnormal mode of operation and is only an informational message.

The settings in the Timing dialog panel can be made permanent by issuing Setup/Save setup menu command. Default values are: 22 kHz, 330 ms and no Disable Warning.

Faster refresh tip:

 Use 11 kHz sampling, 25 ms refresh, check Disable Warning and set YT Single Trace mode.


Colors submenu

The Colors submenu allows to customize Oscilloscope by selecting colors for its different display elements. Colors are chosen by standard Windows ChooseColor  dialog panel. Color settings can be made permanent using the Setup/Save setup menu command.


New features
New features in version 2.51

The new features in Oscilloscope v.2.50 with respect to v.2.30 are as follows:

- All program code rewritten and ported to Win32 platform (Windows95).

- Faster display refresh rate

- FFT mode (Spectrum Analyzer) works on-line, not only in Hold mode.

- Spectrum data can be exported to file or Clipboard

- Special Phase Adjustment function helps working with phase curves

- Better user interface and more convenient Meter function

- Line plot and Scatter plot tracing modes

- Industry-standard 8x10 graticule

- A bug in v.2.50 that made XY Plot mode unusable, has been fixed in v.2.51.


Spectrometer
Spectrum Analyzer (FFT)

The spectrometer is activated by clicking the FFT button or appropriate menu command. It displays the amplitude spectrum of  signal in Y1 channel as Y1 channel and optionally the phase curve as Y2 channel. Use YT Single Trace mode to display only amplitude spectrum or YT Dual Trace to display both amplitude and phase curves.

The phase is defined by phi = atan2( Im(F),Re(F) ), -pi<phi<pi. The spectrometer is fully compatible with Store and Meter commands. Phase is measured in radians, and amplitude in arbitrary units.

To control the appearance of the spectra, use ms/div switch and T slider to change frequency scale, and Y1, Y2, Pos Y1 and Pos Y2 sliders to adjust gain and vertical position of the plots. The software gain of power density spectrum is proportional to the product of the levels of Y1 and Y2 sliders, resulting in both convenient faster-than-linear response (if Y1=Y2 is set) and fine adjustment by a single slider. The amplitude of the phase curve is controlled by Y2 slider alone. Pos Y1 and Pos Y2 sliders govern the vertical position of amplitude and phase spectra respectively.


Armed triggering

Armed triggering allows you to automatically stop the sweep when Y1 level exceeds the preset value. This is especially convenient when working with non-periodic pulses. (Example: clap your hands near the microphone. Armed triggering allows to stop displaying just at the moment you clap; otherwise you would have to ask somebody else to click Hold exactly at that moment.)

Armed triggering mode is activated by clicking Wait button. A red dash will appear at the left of the Oscilloscope screen, indicating the current triggering threshold. This level can be adjusted by Trg Lev slider. Click Line. Now, Oscilloscope will stop when Y1 level is higher than the red dash marker.

To resume sweeping, click Line; clicking the Wait button will turn off the armed triggering.


Oscilloscope screen

Oscilloscope's main screen displays the waveforms fed to the sound card, or their spectra if FFT mode is activated. The colors of both traces and the graticule can be changed from Setup/Colors menu.

The graticule is the standard 8x10 graticule with 90% markings for rise/fall time measurement.


Status area

The status bar displays the current mode of operation (READY, ON LINE, HOLD, DISABLED), WAVE or FFT, and the current level(s) and time/frequency at the cursor position when the cursor is on the Oscilloscope display. If Meter mode is on, the time and level difference between last left and right mouse clicks on the display are shown in the right part of the status bar.

Warning messages are indicated in the bottom right corner of the Oscilloscope display. These warning messages are for information only and do not impede Oscilloscope functioning.


Phase Adjustment  button
Phase Adjustment

The Phase Adjustment button is used to set up the phase angle origin and can be used in FFT Dual Trace mode only. If Phase Adjustment is on, clicking on the phase curve will rotate the whole phase curve in such a way that zero phase angle will correspond to the frequency you’ve clicked at. This can be useful for phase shift measurements. The phase is in the range from -pi to pi, phi=atan2(Im,Re).

Phase Adjustment rotates the complex amplitude by a given angle before arctan is taken. This helps to understand the phase curve behavior across the -pi/pi singularity.


Data file dialog panel

The Data file dialog panel controls the way the data is written to a disk file using File|Save data... command or copied to the clipboard using Edit/Copy data command.

The data is written in two or three columns, and their meaning depends on the  Display Mode switch.

Waveform Options

mode	column 1	column 2	column 3
YT Single Trace	time	Y1	N/A
YT Dual Trace	time	Y1	Y2
XY Plot	Y2	Y1	N/A

So, the first column always contains the X deflection data and the second and third columns are the data for vertical deflection.

The time scale can be either in ADC samples or milliseconds depending on Time Scale switch, and the Length switch controls the data amount written, which can be either the whole last buffer recorded by Oscilloscope (All data) or only a part of it currently displayed (Display). Signal level is always recorded as raw data from the ADC, i.e. integers from -128 to 127, without any processing.

Spectrum options

The Data File dialog panel also specifies options for saving FFT data. Note that in FFT mode data export options are fully controlled from Data File dialog, without regard to the plots currently displayed.

The meaning of the columns is controlled by Data radio buttons:

Data	column 1	column 2	column 3
Amplitude	frequency	amplitude	N/A
Amp-Phase	frequency	amplitude	phase
Re-Im	frequency	Re(A(f))	Im(A(f))

Amplitude is in arbitrary units, phase is in radians.


System Requirements

Machine:	80486 or higher PC
Sound card:	8- or 16-bit stereo sound card (*)
Disk space:	less than 200 Kbytes
Software:	Windows 95 with sound drivers installed and configured

(*) 16-bit sound cards are currently used in 8-bit mode; 16-bit mode will be supported in further releases of Oscilloscope.