Getting Started Page 1 of 17 NanoGiant Oscilloscope/Function-Generator Program Getting Started This NanoGiant Oscilloscope program gives you a small impression of the capabilities of the NanoGiant multi-purpose interface. It demonstrates the ADC and DAC functions. For an complete description of all functions press here. The NanoGiant communicate with your PC/Notebook by means of an high speed USB 2 connection. Before installing the oscilloscope software install the communication drivers. Download the latest version of TUeDACSsetup, press here, and follow the on screen prompts. Then run Setup.exe located in the installer directory on the CD. You must have administrator rights on the PC to install the program. Follow the on screen prompts. The final installation takes up approximately 20 MB of disc space and includes the Run Time Engine of LabWindows CVI. In the START menu of Windows you can now find the NanoGiant Oscilloscope installed: Further help is given in the program when you enable the Show Tooltip option. Right click the trace graph and select Show Tooltips, and move the cursor over a control or indicator. Or press F1 to view this help file. To uninstall the oscilloscope software, open Control Panel and then launch Add or Remove Programs. Find the entry NG Oscilloscope2ch and choose Remove. The program switch to Demo mode when it can't find a NanoGiant. The functionality in Demo mode is limited but gives you an impression of how the windows look like.
NG Main Window Page 2 of 17 NanoGiant Oscilloscope/Function-Generator Program One of the following Windows opens when you start the NG oscilloscope Program. If no NanoGiant is connected the left window informs you that you can run the program in Off-Line mode, the right window shows the connected NanoGiant('s) and let you, in case more NanoGiants are connected, choose which one to use. Pressing the OK button start the main program. Simply click on one of the items below to get further information. Start the Oscilloscope Start the signal generator function Start the digital I/O monitor function Start the Signal analyze function The Off-Line mode runs without hardware and shows only a brief functionality of the available functions. NanoGiant 2 Channel Oscilloscope functions Press the Acquire button to start the Oscilloscope. When two signals are provided to the BNC connectors ADC 1 and ADC 2 on the back panel the graph may look like Figure 1.
NG Main Window Page 3 of 17 Figure 1 Figure 1 shows the Oscilloscope in action. The red trace is the channel 1 data and the green trace the channel 2 data. The functions of the various controls are described in the following paragraphs. Figure 2 Starting and Stopping Data acquisition. Press the Acquire button to start, and the Stop button to stop, data acquisition. The led (10) and the animation (21) are indicating that new data can be acquired. On "slow" computers it's better to stop the animation, right click on the animation to toggle it on and off. If you stop data acquisition two cursors become available. They snap automatically to the
NG Main Window Page 4 of 17 nearest trace, and x-y-t information is displayed in lower left area of the graph. More info on cursors click here. Saving Data. Press the Save Data button (13) to save the current traces. The data file is default stored in the <personal directory>\ng_data directory. During the saving process, the filename is visible in the graph and a green led is displayed at the right of the save data button. When the led turns red, the program failed in saving the data file due to: Disk is full or no write permission. File name is generated as follows: NG_trace_<current date>_<current time>.csv. File Format: ASCII, and comma delimited. Voltage [V] Channel 1 Voltage [V] Channel 2 time[s] 0.000000 0.002340 3.049980 0.000100 0.004560 3.049990.................. Setting the sensitivity of the ADC channels. Rotate the Volts/Div knob (8) for channel 1 and Volts/Div knob (11) for channel 2. The trace and axis of the corresponding channel reflects the changes. Right clicking the knobs returns it to the least sensitive value. To put a channel in auto range mode click on the led s (7) or (12), notice that the color of the range values change from blue to red indicating that the Volts/Div for that channel is not valid anymore. Click the led again to switch of the auto range mode. Setting the Sweep time. The Sweep Time knob (4) affects the sample frequency of the ADC's. Together wit the number of samples it determined the time base of the oscilloscope. Default 500 samples are taken during one trace. The number of samples can be changed by right clicking the Sweep Time knob. An 10 times extended time scale can be realized by pressing the x10 led (20), the Sweep Time knob is then replaced by an Position knob. You can also use the Mouse Wheel to increase or decrease the Sweep Time. And if you press the Shift key and the Mouse Wheel the number of samples is changed. Setting the Display mode. With the Display slide (3) you can switch between the various display modes: Ch1-t: Voltage channel 1 left Y-axis versus time X-axis. Ch2-t: Voltage channel 2 right Y-axis versus time X-axis. Ch1-t & Ch2-t: Voltage channel 1 left Y-axis, Voltage channel 2 right Y-axis
NG Main Window Page 5 of 17 versus time X-axis. Ch1-Ch2: Voltage channel 1 left Y-axis versus Voltage channel 2 X-axis. Axis names and scales are automatically adjusted to reflect the display mode. Setting the trigger mode. With the Trigger slide (5) you can switch between the various trigger modes: Ext: external trigger mode, data acquisition is started after a 5V to 0V transition on pin 16 (Ch1)-18 (Ch2) of the digital I/O connector. When the Display Mode is Ch1- t & Ch2-t or Ch1-Ch2 pin 16 and 18 must both be connected to the external trigger signal. FreeRun: free run mode, the data acquisition is continuous. Int: internal trigger mode, data acquisition starts after an software trigger, right click the slide to display the delay time. Single: single trigger mode, data acquisition of one trace is started after pressing the single trigger button (6). Apply a filter to an ADC channel. The low-pass input filter consists of an 8th order elliptic filter with a software selectable cutoff frequency, in the range 0.76 Hz to 12 khz, and can be used for anti-aliasing. Choose with the channel selector (2) the channel you want to apply a filter to. Choose cut-off frequency. You can also apply a software AC filer. Notice that when you use the AC filter, the filtered out DC component is displayed in the graph. Apply display channel offset ADC channels. Use the slides (19) and (16) to shift the channel trace. Display hidden controls. Control to display Action Number of samples Right click Sweep Time button (4) Delay Time Right click Trigger button (5) Trace statistics Right click graph in Data Analyze window ADC status leds Right click Start/Stop adc led (10) Full window ADC data Double click the graph (15) Info and Print Functions. Right click the graph (15) to display an Popup Menu: Show ToolTips Show info on controls.
NG Main Window Page 6 of 17 Help Brings up this help screen. About...- Pop up About window. Print - Print window to default printer. Back to Top 2 Channel Analyze function Pressing the Analyze button shows a window with the current raw trace data at the top graph, and the power spectrum of the filtered input signal (Power Spectrum) at the bottom. The raw data can be extra "smoothed". Figure 3 Figure 3 shows the power spectrum. With the Channel selector you can select channel 1, channel 2 or the sum of the channels. The top graph shows the chosen trace in the time domain, the bottom in the frequency domain. Use the mouse to move the vertical green graph cursor to an area that you wish to know the peak frequency and its power. These values are displayed in the Output Signal Info section. You can apply different windowing functions (filters) in the Data Window section. Units and scale can be changed in the Output Signal Display section. For more info follow this link. Back to Top NanoGiant 2 Channel Function Generator Start Function Generator.
NG Main Window Page 7 of 17 Figure 4 Figure 4 shows the Function Generator Window, the various controls are described in the following paragraphs. Starting the Function Generator. Switch On-Off button to the On position and the generated signal comes available on the corresponding DAC BNC on the front panel. Synchronizing the DAC's. When you press the sync 1&2 button both dac's are triggered at the same time. Synchronization is lost when you apply an other setting to one of the dac's. Wave Form selector. With the Wave Form selector you can choose one of the 5 predefined wave forms: Sine, Triangle, Square, Sawtooth and Noise. For this wave forms you can adjust the Sample Frequency, Amplitude, Offset and in case Square the DutyCycle of the wave. Additionally there is the load from File option. Press the open file button to load the file in to the DAC memory. The file must be in ASCII and contain 1 column of values between -10.0 and 10.0 [Volt]. A maximum of 2048 values can be loaded. For an example follow this link. Wave Frequency. The Frequency of the output wave form is determined by the Sample Frequency and the Number of samples. Default the number of samples is 500, with a maximum of 1024. When you right click the graph you can edit the number of samples. Back to Top NanoGiant Digital I/O Monitor Function Digital I/O control window.
NG Main Window Page 8 of 17 Figure 5 Figure 5 shows the DIGITAL I/O control window. There are 16 programmable I/O ports. In case the oscilloscope is using the external tigger mode, DIO12 and DIO13 are sacrificed. Bit assignment bit function remark pin 0 DIO0 Input/Output 1 1 DIO1 Input/Output 2 2 DIO2 Input/Output 3 3 DIO3 Input/Output 4 4 DIO4 Input/Output 5 5 DIO5 Input/Output 6 6 DIO6 Input/Output 7 7 DIO7 Input/Output 8 8 DIO8 Input/Output 10 9 DIO9 Input/Output 11 10 DIO10 Input/Output 14 11 DIO11 Input/Output 15 12 DIO12 Input/Output - Trigger input ADC1 16 13 DIO13 Input/Output - Trigger input ADC2 18 14 DIO14 Input/Output - Trigger input DAC1 19 15 DIO15 Input/Output - Trigger input DAC2 20 Back to Top Contact and Information About info window.
NG Main Window Page 9 of 17 Right click the graph and choose About... from the popup menu to get version info. For detailed TUeDACS NanoGiant Hardware Specifications and Software description press here. For more general information press the TUeDACS home page. Or Email Us. Back to Top Back to Top
Controls Page 10 of 17 Explanation various Controls. 1 15 Graph 2 Channel switch filters 16 Offset slider Channel 2 3 Display Mode switch 17 4 Sweep Time selector/ Position 18 Y-axis sensitivity 5 Trigger Mode switch 19 Offset slider Channel 1 6 Single trigger button 20 Extending time scale x10 7 Auto scale Channel 1 switch 21 indicate that data can be acquired 8 Sensitivity selector Channel 1 22 Number of sample/ trace 9 23 Delay time indicator 10 indicate that data can be acquired 24 Offset value AC filter Channel 2 11 Sensitivity selector Channel 2 25 Offset value AC filter Channel 1 12 Auto scale Channel 2 switch 26 13 Save data button 27 14 X-axis sensitivity
Controls Page 11 of 17
Load from file Page 12 of 17 Load file from disk example. 1 Press 2 Choose File from the Wave Form selector and press the open file button 3 Select the dac1ydata.txt file
Load from file Page 13 of 17 4 Right click the graph to view the Number of Samples. 5 Select a Sample Frequency of 1 khz. 6 Switch the DAC On. 7 Repeat this for DAC 2 but select the dac2xdata.txt file. 8 Connect externally ADC-1 with DAC-1 and ADC-2 with DAC-2, press the sync 1&2 button
Load from file Page 14 of 17 9 Right click the Sweep Time knob and change the Number of Samples to 183. 10 Select a Sweep Time of 50 ms/div 11 Right click the Storage button to toggle between lines and dots.
Load from file Page 15 of 17 12 Switch the Display mode selector to Ch1-Ch2. 13 The text TEST ADC DAC OK should appear.
Sampling info Page 16 of 17 Analog Frequency, Sample Rate, and Nyquist Theorem. The Nyquist Theorem states that the highest frequency you can accurately represent is half the sampling rate. For instance, to measure the frequency of a 100 Hz signal, you need a sampling rate of at least 200 S/s. In practice, you should use sampling rates of 5 to 10 times the expected frequencies to improve accuracy of measurements. In addition to sample rate, you need to determine the number of samples to acquire. You must sample a minimum of three cycles of the analog signal. For example, you need to collect at least 15 samples, or points, if you use a sampling rate of 500 S/s to measure the frequency of a 100 Hz signal. Because you sample about five times faster than the signal frequency, you sample about five points per cycle of the signal. You need data from three cycles, so 5 points x 3 cycles = 15 points. In practice, however, you should acquire 10 or more cycles to improve accuracy of measurements, so you should acquire 50 or more samples. The number of points you collect determines the number of frequency bins that the samples fall into. The size of each bin is the sampling rate divided by the number of points you collect. For example, if you sample at 500 S/s and collect 100 points, you have bins at 5 Hz intervals. The Nyquist frequency is the bandwidth of the sampled signal and is equal to half the sampling frequency. Frequency components below the Nyquist frequency appear normally. Frequency components above the Nyquist frequency appear aliased between 0 and the Nyquist frequency. The aliased component is the absolute value of the difference between the actual component and the closest integer multiple of the sampling rate. For example, if you have a signal with a component at 800 Hz and you sample at 500 S/s, that component appears aliased at 200 Hz because 800 (2 x 500) = 200(Hz). One way to eliminate aliased components is to use an analog hardware filter before you digitize and analyze the frequency information. If you want to perform all the filtering in software, you must first sample at a rate fast enough to correctly represent the highest frequency component the signal contains. For example, with the highest component at 800 Hz, the minimum sampling rate is 1,600 Hz, but you should sample 5 to 10 times faster than 800 Hz. If the frequency you want to measure is around 100 Hz, you can use a lowpass Butterworth filter with a cutoff frequency (fc) of 250 Hz to filter out frequencies above 250 Hz and pass frequencies below 250 Hz. Windowing Use windowing, or smoothing windows, to minimize spectral leakage associated with truncated waveforms. Spectral Leakage Spectral leakage is a phenomenon whereby the measured spectral energy appears to leak from one frequency into other frequencies. It occurs when a sampled waveform does not contain an integral number of cycles over the time period during which it was sampled. The technique used to reduce spectral leakage is to multiply the time-domain waveform by a window function.
Sampling info Page 17 of 17 Discrete Fourier Transform (DFT) and Fast Fourier Transform (FFT) are mathematical techniques that resolve a given signal into the sum of sines and cosines. It is the basis for spectrum analysis. Using the DFT/FFT when you sample a noninteger number of cycles, such as 7.5 cycles, returns a spectrum in which it appears as if the energy at one frequency leaks into all the other frequencies because the FFT assumes that the data is a single period of a periodically repeating waveform. The artificial discontinuities appear as very high frequencies that were not present in the original signal. Because these frequencies are higher than the Nyquist frequency, they appear aliased between 0 and fs/2. The type of window to use depends on the type of signal you acquire and on the application. Choosing the correct window requires some knowledge of the signal that you are analyzing. The following table lists common types of windows, the appropriate signal types, and example applications. Window Signal Type and Description Applications Rectangular (no window) Transient signals that are shorter than the length of the window; truncates a window to within a finite time interval Order tracking, system analysis (frequency response measurements) with pseudorandom excitation, separation of two tones with frequencies very close to each other but with almost equal amplitudes Triangle Window that is the shape of a triangle General-purpose applications Hanning Transient signals that are longer than the length of the window General-purpose applications, system analysis (frequency response measurements) with random excitation Hamming Transient signals that are longer than Often used in speech signal processing the length of the window; a modified version of the Hanning window that is discontinuous at the edges Blackman Transient signals; similar to Hanning and Hamming windows but adds one additional cosine term to reduce ripple General-purpose applications Flat Top Has the best amplitude accuracy of all the windows but limits frequency selectivity Accurate, single-tone amplitude measurements with no nearby frequency components Note In many cases, you might not have sufficient knowledge of the signal, so you need to experiment with different windows to find the best one.