DPScope II User Manual
Contents
1. no averaging is selected otherwise it will acquire the given number of records to average over and then stop This means that if you want to do a true single shot capture you need to set the averaging to No Avga In datalogger roll mode single shot and averaging is not available in this case the Run button simply starts the continuous acquisition 2 1 2 Stop Stops the acquisition process 2 1 3 Clear Clears the waveform 2 1 4 Continuous Single Shot Selects whether the DPScope Il shall continuously acquire new waveforms or only acquire once and then stop Continuous acquisition is useful for repetitive waveforms when you want to see if or how the signal changes over time Single shot capture is useful e g for events that happen only once e g a sudden pulse or when you want a steady picture to take measurements on 2 1 5 Averaging Selects how many waveforms to average over 1 2 5 10 20 50 or 100 Averaging reduces random noise on the waveform resulting in a much cleaner picture that allows you to see small details that may otherwise be hidden under the noise For averaging to make sense you need to have a basically stable repetitive waveform so you will need to turn the trigger on i e auto mode won work because the sample timing would be asynchronous to the signal period Note that the averaging process used is not a simple arithmetic average over the given number of samples instead it uses exponential we2. 2 7 File Menu 2 7 1 Load Setup Recalls a previously saved setup all settings like acquisition mode vertical scales time scale trigger setup etc from a file 2 7 2 Save Setup As Saves the current setup i e all settings like acquisition mode vertical scales time scale trigger setup etc to a file 2 7 3 Export Data Exports the currently displayed waveforms to a text file The file contains both scope waveforms CH1 and CH2 as well as both reference waveforms REF1 and REF2 File format is standard CSV comma separated values format which you can open and process in Microsoft Excel or any standard text editor e g Notepad 22 In datalogger roll mode it is usually more useful to select fLog to filedinstead because this will write all the data to the file while Export Datadonly writes the latest screen interval 2 7 4 Exit Closes the DPScope Il application Always close down the application before disconnecting the scope 2 8 Measure Menu 2 8 1 Measurements While it is possible to make measurements on the waveforms using the cursors the DPScope II also offers a faster and much more convenient method Fully automated measurements Selecting Utilities gt Measurements brings up the Measurement panel Here you can select on which channel s CH1 and or CH2 the software shall take the measurements and also which measurements to take The values get updated after every acquisition If you have already acqu
3. Bose RISING Falla BO loans 19 25 3 NOIE TRE CCU rr 19 20 A Sen Re OT ee een ROR Te Pet Onn ee enn et E ae eter 20 2 6 1 GRT CGA2 Channel ONSels cc ir 20 20 2 AS asset certs artless tls lect as tle aes eed as tls aed 21 2 AA A AE EE 22 2 7 1 Lodd Selassie 22 2il 2 Sn A 22 2 3 EXPO ED iaa econ 22 2A berlina 23 29 A A 23 2 8 1 Measures laico sundae atado 23 20 2 SPEcrumANANSIS rd 25 200 DMMDIS Pla V ran 26 as Generator Menta 27 ZNO IA o 28 2101 Probe COMPEASAO N resning E irc 28 AA 30 2 11 Utilities Me Usan a n 31 A alii 31 2 02 A I N 32 Rf A o a 32 1 Introduction The DPScope ll is a low cost microcontroller based digital oscilloscope intended for hobby and educational use It is based on a Microchip dsPIC 16 bit microcontroller Most of the oscilloscope hardware is actually integrated in this single chip 1 analog to digital converters sample logic trigger logic and threshold generation memory serial data interface Only the analog frontend input amplifier attenuator vertical offset generation and the USB interface consist of external components If you are interested in the detailed hardware design check out the DPScope Il webpage www dpscope com where you find the full circuit schematic as well as a description of the hardware functionality and some of the design considerations that went into the development of this instrument If you are new to oscilloscopes we recommend the following intr
4. only be used as a rough guidance or to observe changes in voltage or amplitude rather than absolute values As for timing measurements the accuracy is mostly driven by the clock source which has a spec of around 0 5 2 9 Generator Menu E Signal Generator aja Frequency 1234567 Hz Duty 50 TO kHz 100 kHz 10 0kHz 00 kHz 30 kHz 300 kHz 4UkHz 400 kHz SU kHz 500 kHz BU kHz 600 kHz fUkHz 700 kHz o0 kHz 500 kHz SU kHz 500 kHz The DPScope Il offers a simple frequency generator It output is available at the CAL pin on the back side of the instrument This signal is mainly intended for probe compensation see section below but is also usable for other applications Note that if you connect this signal to a circuit you also need to connect the GND pin with the ground 0V of your circuit Also make sure to avoid applying overvoltage or electrostatic discharges into the CAL output i while it does have protection circuitry inside its protection is not as sturdy as the one for the main scope inputs You bring up the control display through the fGenerator menu This opens up a window where you can change the frequency as well as the duty cycle of the signal dury cycle is the 2 percentage of each period where the output is high The signal levels are fixed approximately OV low and 3 3V high when no load is on the output The output impedance is roughly 1 kOhm so if you want to drive a significant load
5. when you are in X Y 11 display mode if the signals change fast compared to the sample rate connecting subsequent sample points with lines can result in a messy difficult to interpret picture on the screen 2 2 5 Persist Normally the screen is cleared whenever the scope has a new acquisition is to display Checking this option will make the scope keep all waveforms on the screen until you either press rStopoand then rstart Nagain or until you press fClear This allows you to see over which range the waveform is changing important cases are measurement of peak to peak noise or timing jitter This is also a great tool to capture rare glitches sudden waveform aberrations that you may miss otherwise because without persist mode they may disappear from the screen again so quickly that you can see them When persist mode is turned on Nowever even a single such event with remain easily visible Finally a very common application of this mode is to produce so called data eyes for digital waveforms For this purpose choose triggering on fBoth i e rising as well as falling edges for the clock waveform and turning fLinesooff and Mots on 2 2 6 Levels Turns level markers and the trigger position marker in pretrigger mode on and off While the levels CH1 and CH2 offsets and the trigger threshold are also indicated with colored triangle markers on the left edge of the waveform display sometimes it is helpful to have rulers across the
6. a quarter of the vertical display range Note Due to the way the scope is built you cannot change the waveform offset when the input is AC coupled coupling selection in the Vertical frame In this case the waveform center is fixed to the display center To set up the trigger move it to the center of the trigger channel signal band i e the green triangle on the left should be somewhere between maximum and minimum level of the signal CH1 or CH2 i you want to trigger on and turn the trigger on Switching on the rLevelsodisplay can be helpful there as well To quickly move a slider back to center just press the button labeled X reenterd above the respective slider Now you can fine tune your setup e g use a different sampling mode change the trigger polarity etc When you expect to measure the same signal again later you may want to save the complete setup to a file File gt Save Setup that can be loaded back later That way you do not have to repeat the full setup procedure over and over 1 7 Undersampling Aliasing One very common trap that many beginners but not only they fall into with digital sampling oscilloscopes is so called aliasing This effect can happen whenever the sample rate is too slow compared to the signal frequency To pick a simple example assume you have a 1 kHz sine wave that you sample with a 1 ksample sec sample rate In this case each acquisition will hit the same point in the signal period
7. but it can be any port between COM1 and COM99 Hint On some computers the driver seems to have a problems with port numbers larger than 16 If you do see the virtual COM port appear when you plug in the scope see above but the software reports being unable to connect you can manually modify the assigned port number in the device manager to 16 or below make sure not to use a number that is actually used by another device The minimum required screen resolution for the DPScope Il software is 1024x768 pixels 1 3 The Main Screen After startup the screen should look as shown below File Measure Generator Calibration Utilities Help Acquisition Display w Li moc Bo REF pe Lines bold lv CH2 MN I ERA I Dots Clear Persist Cursors T continuous I Levels C single shot No Avg y Xx mode Frequency Spectrum FFT Vertical Voltage Scale Probe Attn Coupling LI 1 CHI 541 div vii ADC T Pa Wati HHEH AE FERIA 444 RRR A A tt RRA A A ERA A A ERE RIA AA AE RRA AE FER FAA A dE Fel CHI CH2 Trig T i Bi xi Ri Horizontal Scope Mode Datalogger Roll Mode a 0 1 ms div v 100 kSamples sec M Pre Trigger Mode Sweep Delay 0 0 divs 0 all Trigger Source e Auto CHI C CH2 Polarity e Rising Falling Both Holdoff o 0 us z V Noise Reject fine 4 gt 0 0 divs 0 s Cursors d Y Y Y The left side of the display is taken
8. fCH10o0r fCH2 the scope will feed the respective channel signal into the trigger circuitry 18 2 5 2 Rising Falling Both The trigger polarity further specifies the required trigger condition Rising means the signal must cross the threshold from below and rise above the threshold i e a positive slope to cause a trigger frFalling means the signal must cross the threshold from above i e a negative slope rBothomeans the scope will trigger on a rising as well as a falling edge Of course this will not produce a steady picture for a repetitive waveform The most common application for this feature is to produce data eyes for digital signals the trigger in this case is the clock signal the displayed signal is the data signal This mode is currently only available in Normal Mode pa DPScope pad DPScope Ele Utilties Help File Utilities Help Trigger on rising edge Trigger on falling edge Trigger Source Auto CHI C CH2 Trigger Source Auto CHI CH2 E r Notse Polarity Rising Falling v Reject Polany Rising W dos Cursors dV Y V Y dt ms 1 dt kH Cursors dY Y Y Y dt ms 2 5 3 Noise Reject If there is noise on the signal and there is always some amount this can cause false triggering E g if triggering on a rising edge the signal may actually be falling at a given instant but a short little positive noise spike right when the signal
9. step to one horizontal unit or if the flineOcheckbox is checked to one sample 1 10 of a horizontal unit The slider visualizes the portion of the record currently displayed on the screen To the right of the slider the time position of the left edge of the displayed range is shown both in seconds and in horizontal divisions zero meaning the start of the acquired record 2 4 2 Scope Mode Datalogger Roll Mode In scope mode the DPScope Il will always acquire a full data set 800 samples per channel and store it in its internal memory before transmitting it to the computer for display This enables very fast sample rates up to 50 MSamples sec in Equivalent Time Sampling Mode because there is no limitation from the transmission speed between scope and computer The downside is that the record length is limited to these 800 points and for very slow sample rates the time between subsequent transfers becomes larger because it takes a while to capture 800 points at a slow rate Datalogger roll mode on the other hand is limited to relatively slow sample rates 1000 samples sec maximum which corresponds to 10 msec div but the length of the acquisition is unlimited you can have the DPScope Il the captured data directly into a text file and thus have virtually unlimited storage 2 4 3 Sample Rate Determines the sample rate i e how many times per second the signals on CH1 and CH2 are measured The available range is dependent on the
10. sweep delay would not make much sense after all you choose this mode to look at the signal before or around the trigger instant so it is replaced by a trigger position selection this lets you choose how much data shall be acquired after the trigger or in other words where the trigger position shall be within the full record You can set the trigger position anywhere from 0 to 100 0 to 80 divisions in the record To display the trigger time check then fLevels checkbox in the Display frame 2 5 Trigger Trigger source de Auto C CHI MEDE Polarity of Rising Falling Bath W Noize Reject 2 5 1 Auto CH1 CH2 The Auto CH1 CH2 radio buttons let you select what the DPScope II shall trigger on A trigger is basically a condition that determines when the oscilloscope starts the data acquisition For a repetitive signal you use this to obtain a steady picture of the signals For a one time signal it allows you to have the scope wait until the event of interest occurs before it starts to capture the signals If set to Muto the DPScope II will be free running constantly collecting data and not wait for any special event before capturing data This is useful when you want to look at an unknown signal because you will always see something on the screen the scope will not wait and not display anything just because some trigger condition is not fulfilled Thus this option is available even in equivalent time mode If set to
11. whole screen The trigger position in pretrigger mode tells you which portion of the waveform caused the trigger 2 2 Cursors CH1 CH2 Turns the measurement cursors on and off respectively and selects which channel CH1 or CH2 they refer to The cursors are the solid horizontal and vertical lines in the waveform display which appear whenever you check the fCursors checkbox You can move them with the slider bars on top bottom and left right of the waveform display or alternatively by clicking on them and then with mouse button pressed dragging them to the desired location The current level and time positions as well as the difference in their positions are shown in the status line on the bottom of the scope window mn a LEJ m Cursors dY 8 602 Y 5 580 Y 3 022 Y dt 308 4 us 1 dt 3 243 kHz Because the voltage scales can be different between CH1 and CH2 you need to select which of these two waveforms the cursors shall refer to The time scale is the same for both so this selection has no bearing on timing measurements i e on the vertical cursors 12 With the cursors you can perform many different measurements on the displayed waveforms for example Levels amplitude high and low level average level overshoot and undershoot Timing period frequency delay phase rise and fall time Note that the DPScope Il also offers a set of fully automated measurements You can access them through Measur
12. you will need to buffer this signal You can however easily drive a high impedance CMOS input of a logic gate or a JFET operational amplifier To change the frequency or the dury cycle click on the Up Down arrows aboce and below the particular digit In addition there are a number of buttons on the bottom of the Signal Generator window that allow you to quickly set a number of common frequencies and duty cycles The frequency is adjustable between 250 Hz and 2 MHz the actual resolution gets coarser with increasing frequency so while the display allows changes in single Hz steps this does not necessarily mean the output frequency will actually change in such small increments 2 10 Calibration Menu 2 10 1 Probe Compensation Selecting this menu item puts the DPScope Il into probe calibration mode The software will automatically set a number of parameters to suitable values horizontal sale turning AC coupling on setting the trigger level the screen center Tthe frequency generator see section above is set to produce a 2 kHz square wave with 50 duty cycle To perform probe compensation attach the probeG signal pin to the CAL output and the probe ground lead to the GND output on the back of the scope The display will show roughly two periods of the calibration signal 3 3V amplitude square wave Depending on the probe you use 1 1 or 1 10 you may need to adjust the vertical scale and offset to get a decently sized signal on the scre
13. 1 1 MOL 2 3 1 Voltage Scale The vertical gain boxes set the input amplifier gain so you can look at very small Millivolts as well as quite large several Volts signals The scaling is displayed in V div Volts per division or mV div Millivolts per division so e g at 1V div each vertical unit interval between two horizontal dashed grid lines corresponds to 1 Volt The settings for CH1 and CH2 are independent from each other The available settings depend on the probe attenuation chosen see below Selecting 1 10 probe attenuation will result in all ranges increasing by a factor of 10 Note that this is only a calculation difference to be correct you must of course actually have the probe set to the particular attenuation The scope has no way of knowing what you have the probe set to 2 3 2 Probe Attenuation The probe attenuation setting 1 1 and 1 10 respectively does not have any bearing on the actual input amplifier setup but rather tells the scope software how it must scale the measured data on the screen A 1 10 probe reduces the signal by a factor of 10 which allows you to measure much larger signals than would be possible with a 1 1 probe To be correct you must of course actually have the probe set to the particular attenuation The scope has no way of knowing what you have the probe set to Due to the way the DPScope ll is designed the probe used 1 1 or 1 10 respectively influences the internal signal off
14. 1 au ae dm cn i oo Pi Pu i mm Sg A L T I E io pa mm i min 1441 500 1421 ale 1610 le A Ti Pa ra l Ta Lu oo LT Pi LO oo JEE 3139333 4 508 L TM m a 551551458 an i In this panel you can tell the software to perform a full gain and offset compensation This is done to ensure optimum level accuracy e g so that zero input voltage really shows up as close to zero on the screen It also acts as a relatively comprehensive functional check of the scope so it is a useful diagnostic tool if you suspect something is broken The set of compensation values is stored in the scope EEPROM and is automatically loaded from there at each program start meaning the software always uses the appropriate values for the currently attached DPScope Il without user intervention You can however reload the values manually reset the values to default this only changes the numbers the PC software uses during the current session not the numbers stored in the scope unless you manually tell the software to write them to the scope etc Level compensation is part of the setup and checkout process before each DPScope ll is shipped so the scope is usable right out of the box without you needing to perform this procedure It can however be a good idea to execute compensation when using a new set of 1 10 probes because it will optimize offset and gain settings for each particular pr
15. DC component so one can look at the AC component with high resolution a large DC component would otherwise force a rather coarse vertical gain setting to allow the signal to be displayed This can be done by adding a suitable capacitor MDC blocking capacitor in series with the signal which is called PAC couplinga The DPScope II has this feature built in and you can activate it on a per channel basis by selecting FACOin the appropriate combobox Note Due to the way the DPScope Il is built you cannot change the waveform offset when the input is AC coupled In this case the waveform center is fixed to the display center IMPORTANT Even though the signal will appear centered around zero volts AC coupling does NOT increase the maximum voltage level 20V you can safely apply to the scope inputs 2 4 Horizontal Horizontal le Scope Mode Datalogger Roll Mode 0 1 me dr 100 kSamples zec Pre Trigger Mode Sweep Delay 0 0 divs 0 EI l 19 7 divs 985 0 us W fine rnamrn Aif Ii f tri f iri ik mrn 1 FAL L LI 16 2 4 1 Record Display Position While the scope acquires records of 800 sample points per channel only a range of 200 points is displayed on the screen To scroll through the full record use the slider below the waveform display shown in the second picture above The slider is set up so that a big step corresponds exactly to a full screen width i e 200 point 4 record and a small
16. DPScope Il User Manual Version 1 0 Jan 8 2015 A ner RIETI Ot hal RIE e E AT DPScope I Lit ind ti Contents 1 A a 1 Li Geremia 1 L2 SollWare StdiUb sarei 1 do TMeS Mal SC eN 3 id WPS A COUISIMON NN Nos 4 AO ACUSAN ES pulci 4 1 5 1 PSII VAN IOC Ose hi ak a a bi o 4 15 2 PRCWIOGE MOS reo 5 1 5 3 Equivalent Time Sampling Mode 5 1204 Datalogger HOM WOO cate elena 6 1 6 Probe Vertical Gain Setup and Trigger Setup i 7 Lee Ungersamping AMA da ana 8 Descripiion ofUSser Controls dello ela 9 Dil A A O O A 9 2 1 1 o ene A E E an E 9 Dede AOD A A ai 9 Ble o e a o e 9 2 14 CONUNUOUS SINGIE LE 10 LN O A ana 10 2 10 A iaia eni 10 22 DISDIAY case EREE EEEE EREE E 11 2 CIRIE IO 11 222 REFER 11 223 gia o o ee Oem me NOOR a eS Tee mm SR A 11 eze CA E COOPER Peo ee e O ESO EE PERO o O O 11 A A e o OO iaia 12 o AS is a ei 12 22 GUISOS Ur tudo 12 a O NOC rae iE a a i ie aah aah he a ata Cita Ba ne ete Mie 13 2 2 9 Frequency Spectrum FFT FFT Setup 14 o A ade Ea eee ea et ee Ea 15 2 3 1 Vollage Scalea aaa 15 232 i ille 15 2393 eo ble 16 A IN 16 2 4 1 Scope Mode Datalogger Roll Mode ooocccoccococnccccncocnccncnconcnnnnnconcnnnanonnnoos 17 2 42 Sample Bali AAA a 17 24 3 Pretrigger Mode 17 2 4 4 Sweep Delay Trigger PositioN e 18 o A i ia 18 2 5 1 AMO Ra iii 18
17. When you want to acquire a new unknown signal it is best to maximize your chances of seeing something before fine tuning your settings Choose the widest voltage range available 1 V div and set the channel offset to the center of the screen That way your visible range spans from 10V to 10V assuming 1 1 probe attenuation which will capture most signals you encounter For larger signal use a 1 10 probe to widen the range even further don t forget to select the proper probe attenuation in the Vertical frame otherwise the displayed signal offset will be incorrect Whenever you use a new 1 10 probe first perform a probe calibration described in section rCalibration 1 1 probes should not need any calibration because the DPScope IIG input has been calibrated for them as part of the scope assembly It is usually best to set the trigger to FAutoOmode otherwise youd have to hunt for a valid trigger level on the invisible waveform before the scope displays anything The waveform timing will not be stable that vay but will move randomly in time i e waveform humping aroundo horizontally but you will be able to see which voltage range the signal spans Using the rPersistenceddisplay mode can sometimes be helpful if looking at rare spikes where the signal amplitude is difficult to judge otherwise Once you know the range you can adjust vertical gain and offset to center the signal vertically and make it fill a good portion at least
18. acquisition mode Normal Mode FFT Mode 1 sec div to 5 usec div 10 Sa sec to 2 MSa sec Equivalent Time Sampling Mode 2 usec div to 0 2 usec div 2 MSa sec to 20 MSa sec Pretrigger Mode 1 sec div to 20 usec div 10 Sa sec to 500 kSa sec Datalogger Mode 10 msec div to 1 hr div 2 4 4 Pretrigger Mode selects between normal mode or equivalent time sampling mode and pretrigger mode In Pretrigger mode you can view what happened before the trigger event up to 80 divisions the tradeoff is somewhat higher jitter and a maximum sample rate of 500 kS sec For more details see the introduction 1 2 4 5 Sweep Delay Trigger Position In normal or equivalent time acquisition mode this slider sets the amount of post trigger delay i e the time to wait after the trigger event before the sampling begins This allows you to look at the waveform some time after the trigger with high resolution without that feature you would have to reduce the sample rate to look at times long after the trigger because the oscilloscope has only a limited sample memory 800 points per channel For repetitive signals this is effectively equivalent to a very large sample memory if you change the slider setting the waveform will simply seem to move left or right You can set the sweep delay to any value between 0 and 200 divisions be careful at slow timebase settings since during the sweep delay the DPScope Il will be unresponsive In Pretrigger Mode such a
19. copy the currently displayed waveform CH1 or CH2 respectively into the respective reference waveform you use the appropriate gt button Reference waveforms are very helpful e g to judge small signal changes by comparing the stored waveform to the displayed waveform Another important application is when you want to compare more than two signals one example would be an SPI bus consisting of clock data and chip select In this case you can first set up the DPScope Il so CH1 looks at the chip select and CH2 looks at the clock signal and it triggers on the falling edge of the chip select signal Capture both signals with single shot mode and save CH2 to REF2 Now connect CH2 to the data line instead and repeat the capture You now have all three signals clock data chip select on the screen at the same time 2 2 3 Lines Checking this option will cause the scope to connect the captured data points with lines This makes the actual waveform much easier to see especially when there are fast changes which would make subsequent points fall on places far away on the screen Use the rBoldooption to make the lines wider e g to be able to better see them at a distance 2 2 4 Dots Checking this option will cause the scope to indicate the actual sample points with small circles This can be very useful if you want to check if your sample rate is truly high enough for an accurate waveform display Second use this mode and turn fi_ines off
20. e gt Measurements 2 2 8 XIY Mode This checkbox changes between normal signal versus time or Y T waveform display and X Y display mode In X Y mode instead of plotting the CH1 and CH2 waveforms against time now CH1 determines the horizontal X position and CH2 the vertical Y position of each point A common application for this is to measure phase shifts e g in order to analyze reactive elements inductors capacitors It is usually easiest to first set up the waveforms in normal Y T mode and only then change to X Y mode In addition usually you will obtain the best picture if you choose fauto trigger turn off rLinesodisplay and turn on fDots and fPersist 4 DPScope II Ele Measure Generator Calibration Utilities Help Acquisition Display Run AN Ca Sto F r i Vv Dots Clear Persiy continuous rey V XA mode Y E f No Avg Vertical Voltage Scale single shot r Levels cne posa gt CH1 CH2 Trig Bi xi Horizontal C Cc 10 us div l 1 MSample sec Pre Trigger Mode Sweep Delay 0 0 divs 0 s ll Trigger Source Auto CHI C CH2 Polarity Rising Falling C Both M Noise Reject Ki gt 0 0 divs 0 s Cursors dV V V V 1 dt kHz 13 2 2 9 Frequency Spectrum FFT FFT Setup Vertical Scale Filter f Hone f logarithmic Hamming Hanning f Blackman Display f Vol
21. e In order of the timing measurements to work at least one full signal period needs to be displayed on the screen e The time measurements employ linear interpolation to improve resolution and accuracy of the results This way the resolution of the measurements is much finer than one sample period e Averaging can significantly improve the accuracy especially for the level measurements e Measurements slow down the acquisition process somewhat Turn them off close the measurement panel for maximum screen update rate 24 Short description of each measurement Low lowest value minimum on the screen High highest value on the screen Mid Midpoint between low and high mid low high 2 DC mean average voltage level calculated over all points on the screen Amplitude difference between high and low amplitude high low AC RMS RMS value calculated with the mid level taken as the reference Rise time time to rise from 10 to 90 of the swing low 0 high 100 e Fall time time to fall from 90 to 10 of the swing low 0 high 100 e Period time between subsequent rising edges crossings of the 50 point mid level or falling edges if there aren two rising edges on the screen e Frequency 1 period e Duty cycle time spent above 50 during one period relative to the length of the period duty_cycle pos width period e Pos width time spent above 50 during one period e Neg width time spent b
22. e calculated spectrum in many cases the peaks are not limited to a single point but spread out over at least two frequency fbins this is called rspectral leakaged with signal fieaking into adjacent bins Thus you can select which width the software shall calculate the total area over and use for the center of mass calculation of the peak The default of 7 means it uses 3 points each to the left and to the right of the peak amp maximum This method ensures a very precise determination of the actual frequencies A setting of 1 is possible but may lead to erroneous results so a minimum of 3 is recommended On the other hand choosing to large a width will include a considerable amount of non harmonic noise in each calculated peak again affecting the accuracy of the results Based on the identified fundamental and harmonic amplitudes the software then also calculates the total harmonic distortion THD sum of all harmonic content i e sum of all harmonic peak areas divided by the fundamental area noise total area outside the fundamental and harmonics divided by the sum of fundamental and harmonic peak areas and the sum of both THD N This is done based on the amplitude voltage spectrum i this is the definition commonly used in the audio area as well as based on the power voltage squared spectrum I as is commonly done for non audio applications Of course all these calculations will only yield realistic results if the acquired waveform i
23. elow 50 during one period The threshold combobox lets you select which set of levels the measurements shall use for rise time and fall time measurements either 10 start of rising egde end of falling edge and 90 start of falling egde end of rising edge of the full swing or 20 and 80 respectively 2 8 2 Spectrum Analysis E Spectrum Measurements A e CH1 CH2 Peak Width pts E Display format E Harmonic Spectrum Distortion 100 00 2 THD audio 46 85 4 55 THD H audio dl dd ea 37318 7 Hoise audio FA THD 71 95 a THD N 22 50 Noise 14 56 4 010 11 59 0 11 4 Fundamental 10 021 kHz nd Harmonic 19 95 kHz 3rd Harmonic 30 06 kHz 4th Harmonic 39 99 kHz oth Harmonic 50 10 kHz 6th Harmonic 60 04 kHz fth Harmonic 70 14 kHz oth Harmonic 80 23 kHz Sth Harmonic 90 17 kHz 10th Harmonic 100 00 kHz 25 This panel is only active when the display is set to frequency spectrum FFT Here the software automatically finds the fundamental frequency the assumption being that what is displayed is a periodic signal as well as the first 10 harmonics It shows both the frequencies calculated as center of mass of the power spectrum and the relative amplitudes corresponding to the area of each peak the fundamental being the 100 reference Due to the finite resolution of the frequency display and the fact that the signal frequency usually will not perfectly match a particular frequency point of th
24. en Refer to the calibration panel below as to how the waveform shall look like after calibration On the probe there is typically a small screw either at the probe head itself or at a small block at the connector end that you use to adjust the probe compensation Since this is a trimmer capacitor you should use a non metal plastic or wood screwdriver to adjust it a piece of metal can detune the setting when it is close which would make it hard to adjust accurately Normally 1 1 probes will not need any compensation the scope has internal compensation trimmers that were already set after scope assembly but if the probes in 1 1 mode do not produce a clean square wave on the screen as shown in the window below the trimmers may have become detuned during transport and you may want to open the scope and re do the calibration there are only two trimmers in the instrument one for each channel so there is no way to pick a wrong one Normally though probe compensation is only necessary before using a new 1 10 probe and the adjustment is on the trimmer of the probe not the one in the scope Each such probe must be adjusted to match the DPScope IIG or any other scopeG input i e it is usually not sufficient if you performed probe compensation on a different oscilloscope 28 pas Probe Compensation Connect probefs to compensation output atthe back of the oscilloscope probe tip to CAL ground wire to GND Adjust the compensat
25. en right away The voltage range is set to maximum ground level centered on the screen continuous mode and trigger in Auto mode meaning the acquisition will run without waiting for a trigger event and so on Attach the probes to some signal source e g the toggling output of a microcontroller Press the fRunobutton You should see a waveform on the screen Since the trigger mode is MAuto most likely the waveform will not be stable but rather jump around Now play around a bit with some of the controls Don be afraid You can break the scope no matter what settings you change The worst that can happen is that you no longer acquire a waveform and or see it on the screen If you get completely stuck simply close down the DPScope Il program and start it again Move the offset sliders and see how the waveforms follow Now move the trigger level slider so the trigger level indicated by a green triangle on the left border of the waveform display is somewhere in the middle of the CH1 waveform the red waveform Now select fCH1 in the trigger control menu That waveform should now be stable assuming you waveform is periodic Try switching between rising and falling edge trigger Now change the sample rate in the Horizontal control display and see how the waveform changes it like zooming in and out on the waveform timing Move the Sweep Delay slider and the waveform moving left and right In the Display control box turn the waveforms
26. g Ri sl El 2 6 1 CH1 CH2 Channel Offsets Sets the channel offset for input channel 1 and 2 respectively This lets you control where ground zero Volts is displayed on the vertical axis First this expands the available voltage range for a given vertical resolution e g at 1 V div you could for example cover the range from OV to 20V or alternatively from 20V to OV A second use for the offset is to move the two waveforms CH1 and CH2 apart on the screen so they are easier to discern even though in reality they cover similar voltage ranges e g OV to 5V 20 The zero position for each channel is indicated on the left side of the waveform display with a colored marker red for CH1 blue for CH2 If fievels is turned on in the display control frame two dashed horizontal lines of same colors are drawn across the display as well at that vertical position see picture below To quickly move a slider back to center just press the button labeled X reenterd above the respective slider Note Due to the way the DPScope Il is built you cannot change the waveform offset when the input is AC coupled In this case the waveform center is fixed to the display center and the respective offset slider becomes inactive greyed out 2 6 2 Trg Trigger Level This slider controls the trigger threshold If the DPScope Il is set up to trigger on one of the channels CH1 or CH2 a trigger event occurs whenever the signal crosses this thres
27. has crossed the trigger threshold from above will look like a rising edge to the comparator and cause a trigger even though it is not a true positive edge As a result the oscilloscope will trigger on a falling edge instead of a rising edge The fNoise Rejectofeature avoids this by requiring that the signal must remain above the threshold in the case of a rising edge trigger below for falling edge for at least half a division i e 5 samples If it fails to do so e g because the edge really was just a short noise spike as discussed above the trigger event will get suppressed and the DPScope II will keep waiting for a trigger 19 This feature is especially valuable for slowly varying signals Note however that if your signal period becomes shorter than about one division activating the noise reject feature may prevent the DPScope Il from triggering at all In this case either turn the feature off or increase the sample rate so the period becomes a larger fraction of the screen width HINT Similarly it is recommended to turn off Noise Reject in Equivalent Time Sampling Mode Using this mode means that you want to look at a quickly changing waveform anyway and since the true sample rate is limited to 1 or 2 MSamples sec with a corresponding noise reject interval of 5 usec or 2 5 usec respectively chances are high the noise reject feature more often than not will prevent signal acquisition in this mode 2 6 Levels Levels CHI CH2 Tri
28. her mode the scope simply reports when it has acquired a full waveform Thus as long as the input signal is repetitive you will hardly notice any visible difference between Normal Mode and Equivalent Time Sampling Mode There are however a few tradeoffs connected with equivalent time sampling First there is the necessity that the signals be repetitive with respect to the trigger Second you always need to use a trigger to get usable waveforms otherwise subsequent partial captures will be unrelated timing wise and the composite waveform on the screen will look like random noise rather than the waveform you expect Also it obvious that you can make single shot acquisitions in this mode the software allows single shot mode but here it means that one full waveform consisting of several partial captures gets acquired and then the acquisition stops Still given the fact that most signals one encounters are repetitive or can be made repetitive for testing purposes e g sending a data packet over and over again means that in practice these restrictions are far less serious than you might think 1 5 4 Datalogger Roll Mode For very slowly varying signals it takes a long time before a full record has been acquired E g at 1 sec div timebase each acquisition 80 horizontal divisions takes 80 seconds plus the time it takes before the first trigger event after the end of the previous acquisition happens so you may wait over a minute before
29. hold with the desired polarity rising or falling edge respectively or both rising and falling The trigger level threshold for the chosen trigger channel is indicated on the left side of the waveform display with a green marker If fLevelsois turned on in the display control frame a green dashed horizontal line is drawn across the display as well at that vertical position Usually the best approach with an unknown signal is to first display it with trigger in MAuto mode That way although the waveform on the screen will not be stable I you can at least Judge the voltage range that the signal spans and set the trigger level marker somewhere within that range before setting the trigger source to the appropriate channel see picture below To quickly move the trigger slider back to center just press the button labeled X ftenterd above the slider 21 File Measure Generator Calibration Utilities Help Acquisition Display Y Lines CHI _ gt REI x e s NV bold Fea B 6 RE I Dots Clear a Cursors gt continuous M Levels C single shot er riot No Avg IM XA mode 7 Vertical Voltage Scale ProbeAttn Coupling Ev Bi XI xi Horizontal C C a US dalida v 500 kSamples sec fr Pre Trigger Mode A _ Trigger Patio 14 5 divs 290 0 us E Trigger Source Auto CHI C CH2 Polarity Rising Falling Noise Reject E O p 0 0 divs 0s Cursors dV V Y Y
30. ighing i e earlier acquisitions have less weight than the more recent ones This is the digital equivalent to an analog R C low pass filter but unlike a filter in your signal path it will not degrade your signal bandwidth or rise time it will just filter out fast changes from one capture to the next but not fast changes along the waveform If the signal has changed and you have selected a large average but don want to wait until the displayed waveform slowly settled to the new shape simply press fClear to restart the averaging process starting with the most recently acquired waveform Averaging is only available in scope mode not in datalogger mode 2 1 6 Log to File This function is only available in datalogger mode It allows you to write all the captured samples directly into a file This way you can record signals of arbitrary time spans and with an arbitrary number of sample points no longer restricted to the DPScope IIG 800 points per channel record length 10 2 2 Display Display iw Lines Iw CHI o REFI bold Y cH es I REF2 I Dots Persist fa AS Levels vY mode Frequency Spectrum FFT 2 2 1 CH1 CH2 Turns the display of scope channel 1 and 2 on or off respectively Note that this does not affect the signal capture itself meaning you can still trigger on a channel even when it isn displayed 2 2 2 REF1 REF2 Turns the display of reference waveform 1 and 2 on or off respectively To
31. ion trimmer of the probe for the cal trimmer inside the scope so thatthe displayed waveform Is a sharp square wave without any overshoot and without any slow dribble up see pictures below Close this window to go back to normal scope mode wrong overcompensated correct wrong undercompensated 29 2 10 2 Level Compensation das Level Compensation 2 q A i ib FO 6 E Restore Load Yalues Save Values Unlock Comp Sanity Check TE i Defaults from Scope to Scope Yalues Yalues A caverta 1 0098 CH2 gain correction i 0099 Serial Number 12345 Averaging 20 Gain tolerance 7 5 N per aap Compensation Date 2015 01 06 11 48 DAL tolerance 5 ADC tolerance 2 E DC 1x DC 10x CH Dac abc DAC ADC 1610 A E o E CI T m C1 I E C7 T 7 C7 max 1440 512 1441 508 1440 513 508 Scale 1441 511 1441 510 1441 507 1 um I Pi J i dm LT J Pa sal Ti a Lu dm ll Pi ll al 2 n est m 1 um l Pi um l Mu k l mm l qm au Qi Lan Gu Qi Lan i um mk Pi l l l 1 Ti di qn im iT 7m im um um Fu um um um im ud co nl ll ll Pi dm il DJ im a uo a 1 503 g Pa T im u Pa im pe A Pi um um L J Mai Pi m m Li Li T dui dm L 2i Scale 143 512 A 1 Ti J Pa ki 5 7 g mir T a l E im m Zi T oo T 1
32. ired the signal and only afterwards bring up the Measurements panel simply press Update Values to perform the calculation based on the currently displayed waveforms Do not change vertical or horizontal settings like gain or offset between the acquisition and the calculation The following measurements are available Level low high midlevel DC mean amplitude and AC RMS Timing rise time fall time period frequency duty cycle positive width negative width You can turn the waveform annotations on and off for each channel with the respective PAnnotate checkbox If turned on and the channel is displayed they will show the low mid and high level that the software uses This can be a valuable tool to troubleshoot your results 23 ssa Level Y CHI M CH2 WwW Low 22 07 mu 5 008 4 F nn Ww High safe 4 900 Y i i ir rr Probe Attn Coupling w Mid 4979 N fll mv en re E se eE gt I jf DC Hean BOY 19 03 m WwW Amplitude 9 996 y 9 996 y 7 AC RMS 3 T Cursors W V t m I Rise Time 29 37 us 23 17 us 73 60 us 199 5 us 5 013 kHz 50 1 100 00 us 99 50 us I Fall Time 2947 us x Period 100 00 us Frequency 10 000 kHz Duty Cycle 50 0 al axl Pos Width 50 00 us I Neg Width 50 00 us x de gt ar ZI Le gt zi 100z w Select All Unselect All i i Update Values Important notes
33. just one period later each time so the displayed waveform on the screen will be a flat horizontal line rather than a sine wave clearly wrong If the signal frequency is a steady 1 1 kHz and the sample rate is 1 kHz each sample will be 1 10 of a period offset along the waveform and the resulting displayed waveform will be a very convincingly looking 100 Hz sine wave this can be very misleading Incidentally this is in fact a variation of the equivalent time sampling process called ftoherent undersampling and is widely used whenever one can get sufficient sample rate to sample incoming high speed signals in real time The solution is of course to sample the waveform with a sufficiently high sample rate So if in doubt change the sample rate and see if the waveform behaves mormallyo e g when doubling the sample rate the displayed frequency of the signal should not change And as a general guideline when working with an unknown signal always start looking at it with maximum sample rate and only then change it to something slower 2 Description of User Controls 2 1 Acquisition Acquisition Run a No Ava Log ta file 2 1 1 Run Starts the acquisition process data is captured if trigger event occurs and displayed on the screen If feontinuous is selected the acquisition will repeat until Stop is pressed In case of rsingle shotoacquisition the scope acquires and displays only one record and then stops if No Avg
34. n is very fast again Sweep Delay is not available in this mode since this feature would not make much sense after all if you want to look at things happening a while after the trigger it is better to use Normal Mode anyway The additional versatility of this mode comes with two tradeoffs compared to normal mode First the sample rate is limited to a maximum of 500 kSamples sec because in addition to sampling and storing the signal the scope now must continuously look out for trigger events at the same time This is still good enough for the audio range and a bit beyond up to about 50 kHz Second since the acquisition is completely asynchronous to the signal to be measured there is a 1 sample uncertainty as to how the actual trigger lines up to the sample timing This results in increased trigger jitter i e the waveform on the screen will wiggle back and forth by one sample interval 1 10 of a division 1 5 3 Equivalent Time Sampling Mode This mode works similar to Normal Mode in the sense that the acquisition is initiated by the trigger event so again you can only look at things that happen some time after the trigger But other than Normal Mode in Equivalent Time Sampling Mode the scope makes no attempt to sample the signals in a single sweep Instead it uses its maximum real time sample rate 1 MSample sec or 2 MSample sec to capture one or two samples every microsecond then 5 waits for the next trigger and captures a seco
35. nd record and so on For each record it waits for a slightly longer time after the trigger before it starts sampling this delay can be controlled in increments much finer down to 20 nanoseconds i e 1 50 of a microsecond than the smallest real time sample interval 0 5 us That way assuming the waveform is repetitive with respect to the trigger 1 the sample points of subsequent record will interleave each other with respect to the actual signal timing Plotting them together suitable shifted by the respective added delay versus the trigger produces a picture of the signal with finer resolution than possible with real time sampling Once the delay has spanned one full real time sampling interval one microsecond or half a microsecond respectively the DPScope Il restarts the acquisition delay from zero delay The main advantage is that you can resolve the signal in much finer increments up to 50 MSamples sec or equivalent time sample intervals of just 20 nanoseconds than possible with real time sampling This process of interleaving several acquisitions is implemented in the scopeG firmware i e running directly on the microcontroller resulting in very fast and efficient execution so the resulting frame rate number of full waveforms acquired and displayed is virtually as high as in Normal Mode the PC software does not even need to fknow that acquisition for fast equivalent sample rates is different from slower sample rate in eit
36. obe To perform this compensation you will need a set of two switchable 1 1 1 10 probes Normally the process is fully automated apart from you attaching the probes and connecting them as prompted during the compensation execution but except for serial number and compensation date you can choose to manually override some or all of the compensation values For this press Unlock Comp Values Note While you cannot physically damage the scope no matter which values you enter you directly affect the accuracy and validity of the scope measurements so do this with care After finishing your changes press this button now labeled Lock Comp Values again to guard against further modifications As mentioned above the values will be lost when you shut down the software unless you explicitly write them to the scope press fbave Values to Scope to do that anity Check ValuesOcompares them to the expected ideal values and highlights in red any that are outside the defined tolerances 30 To start the compensation process press the r tartobutton of the level compensation panel and follow the instructions on the screen At the end provided all values look reasonable the software performs a sanity check against the ideally expected values using the tolerances given in the appropriate boxes the scope will write the new values to the scope If there are problems with the results the software highlights red background the values that are outside the
37. oductory application notes created by Tektronix one of the major oscilloscope manufacturers for the professional high end market which will supply all the knowledge necessary to understand this user manual and get the most from your DPScope Il The XYZs of Oscilloscopes The ABCs of Probes You can download both documents either from the Tektronix website hitp www tektronix com or from the DPScope Il website http www dpscope com gt Downloads If after reading through the documentation you still have questions regarding the DPScope II or want to provide feedback or suggestions for improvement do not hesitate to contact us at support dpscope com 1 1 General Remarks The DPScope II is a digital storage oscilloscope refer to the XYZs of Oscilloscope mentioned in the introduction if you are unsure what that is 1 2 Software Startup The software needs the VCP virtual COM port driver from FTDI in order to connect to the scope Normally this driver is already included with Windows 7 and up or will install automatically through Windows update If that is not the case you can also download it directly from the manufacturer http www ftdichip com Drivers VCP htm After you installed the USB driver and the DPScope Il software plug in your DPScope Il and wait a short time so the computer has a chance to recognize the scope The DPScope Il power LED on the front panel should blink quickly a few times and then stay solidly on
38. on and off by clicking on the appropriate checkbox you can still trigger on a waveform even when it is not displayed Change the display style to points and or infinite persistence Congratulations you have just measured your first signal with the DPScope II 1 5 Acquisition Modes The DPScope Il acquisition engine has four different modes again refer to the XYZ of Oscilloscopes document for further details 1 5 1 Normal Mode Acquisition is started by a trigger event or automatically right after the previous acquisition if the trigger mode is fAutod and samples the signal in real time This is very similar to how a classic analog oscilloscope operates Real time acquisition means the acquisition is very fast up to approx 30 records per second on a sufficiently fast computer and you can capture single shot events Note that the acquisition rate will decrease for slow sample rates slower than 50 kSamples sec or 0 2 ms div because it takes some time to simply capture each full record if only a few samples are taken per second Since this mode uses an interrupt generated by the internal hardware comparator the timing is very tight i e reaction to the trigger event is almost instantaneous resulting in very low jitter against the trigger in practice that means there is very little horizontal timing fwiggledof the displayed waveform If the waveform has only little noise this can sometimes look like the acquisition has sto
39. pped because you only see a steady picture You can check that it is indeed running by e g increasing the number of averages combobox in the Acquisition frame and ensuring the number bellows counts up Normal mode has two limitations First the maximum sample rate is 2 MSamples sec 2 million samples per second because the controller has to digitize and store the data as fast as it comes in up to four Megabytes of data per second since there are two channels Second since the trigger initiates the capture process you can only look at things that happen after the trigger unless you can supply a suitable pre trigger signal to the second channel to trigger on If the waveform is periodic you may be able to use the Sweep Delay feature to trigger on one edge but look at the following one to get around this limitation 1 5 2 Pretrigger Mode In this mode the acquisition runs continuously until the trigger event e g the waveform crossing the trigger threshold from below i e a rising edge After the event it Keeps sampling for a user defined time between zero and one full record length and then stops transferring the captured data to the computer This means you can now also look at things that happen before the trigger which often is the interesting part e g the things that precede a wrong data bit Since the acquisition is again happening in real time in this mode you can look at single shot non repetitive signals and data acquisitio
40. s indeed periodic 2 8 3 DMM Display 43x DMM Display Measurement Update rate 2 per sec 10 000 kHz While the automated measurement panel is convenient sometimes you may want to observe only a specific value This could be e g to trim the frequency or the amplitude of an oscillator Chances are you do this at some distance from the screen so it is important that the display is 26 large enough to be observable without being right in front of the computer This is the purpose for the DMM Display window DMM stands for Digital Multimeter because this mode has very similar functionality to such an instrument There you can select a single measurement out of all the measurements available in the main measurement panel on one channel which will then show up in very large digits The update rate lets you select how often the value will get updated if the acquisition rate is slow then of course the update rate will be slower than selected but it will never be faster This makes the numbers easier to read since they don jump around wildly One side note keep in mind the DPScope like any other oscilloscope is an instrument mainly geared towards display of signal changes over time not as a voltmeter Thus the voltage accuracy or resolution cannot compete with a dedicated DMM it is limited by the accuracy of the input divider resistor the internal voltage reference and several other factors so it should
41. set Thus it is important to always select the true probe attenuation i e it is NOT correct to select e g 1 but use a 1 10 probe the displayed signal will have an incorrect offset e g when shorting the probe to ground the display will show a signal levele offset from zero volts 15 IMPORTANT WARNING While the scope can display signals between 200V and 200V with a 1 10 probe which reduces these signals to a range between 20V and 20V you must exercise extreme caution when working with such large signals as a rule of thumb anything that exceeds 20V is potentially dangerous If you accidentally touch the source you can seriously hurt yourself or even die To avoid damage to yourself the DPScope II and or your computer always verify that the probe is truly set to 1 10 mode before contacting the circuit with the probe Note that as also stated in the disclaimer on our website the DPScope ll is not intended for high voltage applications and as a result we decline any responsibility for damage or injury resulting from such work with high voltages you do this at your own risk 2 3 3 Probe Coupling In some cases the interesting portion of the signal is only that part that changes One example is the measurement of noise maybe just a few mV riding on a circuit amp power supply voltage several Volts or some audio signal where components below 20 Hz are not audible anyway In these cases one wants to suppress the steady
42. tage f Power Vector 4verage Checking the fFFTOoption will change the display to frequency domain The oscilloscope performs a real time FFT Fast Fourier Transform on each captured record and displays the resulting frequency spectrum This is a highly useful mode to analyze periodic signals or to find small periodic components e g periodic noise from the power line hidden in the main signal it is much easier to see an isolated 50 or 60 Hz component spectral line in a frequency plot than it is to see it among all the random noise riding on the signal Another common application is to look at harmonic signal content e g stemming from distortion in an amplifier Note that in FFT mode the scope alternates the signal capture between channels i e only captures one channel at a time It does that so it can acquire a longer data record 1024 points which results in finer frequency resolution You can still freely choose which channel to trigger on i e also trigger on a channel when it is not displayed Similar to X Y mode it is usually easiest to first set up the waveforms in normal time domain mode and only then change to FFT mode Also in most cases FFT mode works fine in fauto trigger mode as long as the waveform is periodic and with sample rates low enough so several signal periods are displayed on the screen However make sure that your sample rate is at least 3 4 times your signal period otherwise aliasing will occ
43. the screen refreshes just once In this case it is usually better to display each sample right when it comes in This is what the Datalogger Mode Roll Mode is for The scope acquires the signals continuously and plots the samples on the screen right away The waveform scrolls to the left and the new points get added to the right similar to how a classic datalogger would draw curves on a moving band of paper from a roll that where the Roll Mode has its name from There is no trigger available in this mode since we do not want to wait for a trigger event anyway But you can log the captured data into a text file on your hard drive so unlike the other three modes you can capture data sets of arbitrary length only limited by the free space on your hard drive Clearly this mode only makes sense for relatively slowly varying signals so the sample rate is limited to 1000 samples per second timebase 10 msec div or slower Still this is fast enough to resolve things happening at line frequency 50 Hz or 60 Hz meaning 20 or 17 samples per period Again sample timing is done by the microcontroller ensuring very steady and precise timing not affected by Windows activity only limitation i once the PCs sample buffer of around 8000 samples runs full samples will be lost but even at fastest sample rate this gives a buffer of several seconds The scope software will alert you if that happens 1 6 Probe Vertical Gain Setup and Trigger Setup
44. this is the sign that the scope has successfully powered up Then launch the PC software Start gt DPScope Il gt DPScope Il After a few seconds the DPScope Il program should appear on the screen If the program cannot connect to the DPScope Il you will get a popup see below that you need to confirm in order to continue The software will still start after that but you will not be able to run the acquisition In this case close the software unplug the oscilloscope plug it in again you may want to try a different USB port if that does not help and launch the software again Could not find any instrument attached to the computer Please make sure the unit is turned on and connected to the computer The DPScope Il should always be attached to a USB port directly at the computer or through a powered USB hub Unpowered USB hubs tend to have excessive supply voltage drop which can potentially create problems and or lower the scopeG performance The scope connects through a so called virtual COM porto VCP meaning that while the physical connection is USB the interface driver makes the connection look like a legacy RS 232 COM port You can see such ports under ACOM and LPT ports in the Windows device manager To find out which virtual COM port the DPScope Il uses go to Utilities gt Comm Setup in the DPScope Il program the software will automatically detect which port the DPScope Il is connected to in the example below it is COM2
45. tolerance and you will get prompted as to whether you want to overwrite the currently stored values nevertheless 2 11 Utilities Menu 2 11 1 Comm Setup Displays the virtual COM port the DPScope Il is connected to Since detection is automatic the rManualosetup feature is currently always grayed out C0M14 31 2 12 Help Menu 2 12 1 About Here you can find version and build date of your software the version of the scopeG firmware and finally the serial number of your scope please always include this information when submitting bug reports or support requests The panel also shows the support contact info Fy About DPScope I DPScope ll Oscilloscope Version 1 2 2 Build 2014 12 27 Scope Firmware Version 1 4 Scope Seriali 12345 C 2014 by Wolfgang Maichen Email supportaidpscope com Web http dpacope com 32
46. up by the waveform display and a scroll bar to move through the acquired waveform the record is longer that what is displayed On the right side you can see that the controls are grouped in several functional blocks we will explain each of them in more detail later Acquisition Main control of acquisition process Display Determines how the acquired data is to be displayed Vertical Controls the input amplification attenuation for each of the two input channels Levels Sets the voltage offset for each channel and the trigger threshold level Horizontal Controls the sampling speed delay and sampling method Trigger Defines the trigger source On the bottom there is a status line that displays the cursor information right now the cursors are turned off which you use to make measurements on the displayed waveforms e g to determine the signal amplitude or frequency On the top of the screen you find the menu containing three several File to save the displayed waveforms in numerical format and to save and restore the DPScope Il software settings Measure automated measurements on the waveform and the frequency spectrum Calibration gain and offset compensation and probe compensation Utilities connection info and Help displays general info about the software and about the scopeG firmware 1 4 First Acquisition After startup the software is set up in a way to maximize you chance to see something useful on the scre
47. ur resulting in erroneous frequency domain pictures higher frequency components will get fmirroredointo the display range at the so called Nyquist frequency which is half your sample rate You can use the cursors to make measurements of frequency and relative power Note that the sample rate box changes to frequency units Hz and kHz In addition to cursor measurements the DPScope Il software offers fully automated spectrum measurements which you can access through Measure gt Spectrum Analysis It can automatically identify the frequency and strength of the fundamental frequency and its harmonics and calculate total distortion and noise These features are described in more detail in the respective section below selecting the frequency spectrum display also brings up a small panel where you can modify the settings used for the FFT conversion Linear V vs logarithmic dB scaling voltage vs power the filter type to use and finally the averaging method The filters reduce artifacts caused by the finite length of the data set The available types from top to bottom none 14 Hamming Hanning and Blackman result in increasingly accurate amplitudes for the price of increased spectral line width At the moment FFT mode is only available in real time and equivalent time sampling mode not in pretrigger mode or datalogger mode 2 3 Vertical Yertical Voltage Scale Probe Attn Coupling cor Hi wde lia Joc CH2 12 div
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