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Review by Mauro Grassi ATTEN ADS7062CA Digital Storage Oscilloscope The ADS7062CA Digital Storage Oscilloscope from ATTEN incorporates many features found only in dearer oscilloscopes. It represents very good value for money and its bandwidth is high enough for most applications, including video. T he ADS7062CA is a dual channel colour 60MHz DSO with real-time sampling up to 1GS/s. It is rare to find a comparable DSO at this price range that also boasts a colour screen. The display is a 5.7-inch quarterVGA colour LCD with adjustable contrast. Considering all the functions available, the front panel has a simple and easy-to-follow layout. The vertical attenuator and trace position knobs are colour-coded (yellow and cyan) to match the corresponding traces on the screen. All the knobs are digital by the way; there are no potentiometer controls, which means they should be durable and reliable. The vertical attenuator knobs work in two modes. The standard mode gives the usual 1:2:5 sequence from 20mV/div to 50V/div. Pressing the knob then provides a vernier function, to give much finer control, allowing you to shows the measured waveform using the full screen, for example. Three BNC inputs are accessible from the front, rated at 300V RMS, one for each channel and one for an external trigger. The scope does not have probe sensing but you would not expect that feature on a low-cost scope. Seven of the buttons are backlit, together with an indicator for the multi-purpose User Select knob which adjusts Fig 1: the yellow trace shows a PWM signal at around 3.48kHz. The cyan signal is the output at the drain of a Mosfet connected to a motor being switched by the PWM signal. Five measurements are shown at right. The large spikes in the back-EMF of the motor are visible and are measured to be as high as 65.6V. Fig 2: the same set-up as in Fig 1 but showing the vital statistics of channel 1 on the screen. The peak-peak voltage, frequency, period and average voltage are shown. The trigger level can be read at the bottom of the display, showing the trigger is a rising level above 6.4V on channel 1. 16  Silicon Chip siliconchip.com.au a range of functions. Auto Set & measurements Although most digital scopes incorporate some kind of AUTO set feature, the ADS7062CA is unusual because it Fig 3: the same set-up as in Fig 1, but showing more detail of the switching waveforms. Ringing in the output of the Mosfet is visible and the rise time is measured to be 110ns. Compare this with the fall time of 10ns measured on the gate of the MOSFET to the right. siliconchip.com.au gives the user four additional options after the AUTO set has been completed. These options are especially useful when viewing periodic waveforms. For example, one can choose to show only one complete cycle of a periodic waveform, or only the rising or falling parts. Fig 4: a PWM signal at approximately 3.48kHz. On screen cursors are used to measure the positive pulse width. The pulse width is shown to be 96ms in the window at top right. The values of the two horizontal cursors also appear in this window, relative to the trigger point at the centre of the screen. February 2008  17 The ADS7062CA can make all the common measurements, with up to five independent measurements displayed at any one time to the right of the main window. When using the AUTO set feature, the measurements are shown on the screen, at bottom. The measurements apply to one of the two channels and show peak-peak voltage, period, frequency and average voltage levels. The channel that is selected is the current triggering channel. Alternatively, all measurements can be displayed at once, in a semi-transparent window in the centre of the screen. An independent 6-digit frequency counter appears at the bottom right of the screen. Maths function The ADS7062CA has maths functions on a par with higher end oscilloscopes, including FFT. The two traces can be added, subtracted, multiplied and divided and the result shown as a separate red trace on the screen. Apart from arithmetic functions, the FFT (Fast Fourier Transform) can be used to analyse the frequency components of a waveform. At the fastest timebase setting, the scale goes up to 12.5GHz! However, the magnitude accuracy at frequencies near or above the bandwidth of 60MHz will be poor. The FFT implemented on the ADS7062CA is quite good and the only difference with FFTs on other oscilloscopes we have seen is that you cannot view the FFT and the waveform simultaneously on the screen. However, the ADS7062CA implements a FFT zoom feature that is often lacking in other oscilloscopes. It is particularly handy for examining the frequency components in closer detail, providing up to x10 magnification. A further way to make measurements is via the on-screen cursors. Two cursors are available in either vertical or horizontal mode and are adjusted by turning USER SELECT knob. The cursor values (eg, time, voltage) and the difference between them are shown in the top right-hand corner of the display. Interestingly, you can use the cursors on the MATH function or a previously stored waveform. Acquisition modes The ADS7062CA implements three acquisition modes. In normal sampling mode, the scope acquires samples (of 8-bit vertical resolution) at constant periods as set by the timebase setting. Peak detect mode is good for viewing waveforms that are rapidly changing relative to the chosen timebase period. It detects peaks of the waveform and is therefore well suited to viewing waveforms where there are very narrow peaks that can easily be missed in normal sampling mode. The trade-off is lower noise immunity. For improved noise immunity you can resort to the average sampling mode, in which up to 256 sweeps (selectable) of the waveform are averaged out. This mode is particularly good for seeing overall trends while ignoring unwanted noise. Triggering Featured triggering modes include edge, pulse and video triggering. The SET TO 50% button can be used to quickly set the trigger level halfway between the vertical range of the waveform. This is an easy way to stabilise a waveform on the display. From there, you can adjust the trigger level with a knob. Triggering can be AC or DC-coupled and filtered for better Radio, Television & Hobbies: the COMPLETE archive on DVD YES! NA R MO E THA URY ENT QUARTER C NICS O OF ELECTR ! Y R O T IS H This remarkable collection of PDFs covers every issue of R & H, as it was known from the beginning (April 1939 – price sixpence!) right through to the final edition of R, TV & H in March 1965, before it disappeared forever with the change of name to EA. For the first time ever, complete and in one handy DVD, every article and every issue is covered. If you’re an old timer (or even young timer!) into vintage radio, it doesn’t get much more vintage than this. If you’re a student of history, this archive gives an extraordinary insight into the amazing breakthroughs made in radio and electronics technology following the war years. And speaking of the war years, R & H had some of the best propaganda imaginable! Even if you’re just an electronics dabbler, there’s something here to interest you. • Every issue individually archived, by month and year • Complete with index for each year • A must-have for everyone interested in electronics Please note: this archive is in PDF format on DVD for PC. Your computer will need a DVD-ROM or DVD-recorder (not a CD!) and Acrobat Reader V6 (free download) to enable you to view this archive. This DVD is NOT playable through a standard A/V-type DVD player. Exclusive to SILICON CHIP ONLY 62 $ + $ 00 7 P&P HERE’S HOW TO ORDER YOUR COPY: BY PHONE:* (02) 9939 3295 9-4 Mon-Fri BY FAX:# (02) 9939 2648 24 Hours 7 Days <at> BY EMAIL:# silchip<at>siliconchip.com.au 24 Hours 7 Days BY MAIL:# PO Box 139, Collaroy NSW 2097 * Please have your credit card handy! # Don’t forget to include your name, address, phone no and credit card details. 18  Silicon Chip BY INTERNET:^ siliconchip.com.au 24 Hours 7 Days ^ You will be prompted for required information siliconchip.com.au noise immunity. Either high or low frequencies can be attenuated. The trigger source can be either channel, external source or from the 50Hz mains. Video triggering works with both PAL and NTSC and can synchronise on even or odd fields, or both. Windowing Mode The ADS7062CA incorporates a simple windowing mode, which can be considered a zoom feature. The limits of the window are set with a horizontal knob, while pressing a button makes the window fit the display. User Interface The user interface is typical of most digital oscilloscopes, being organised as a hierarchy of menus with each having sub-menus which are accessed by five “soft” buttons on the edge of the screen. An audible beep informs you when you have set a knob beyond its range, although the beeping can be disabled and a visible cue used instead. Save and recall Up to ten waveforms can be saved and recalled for later analysis. Saved traces are recalled to the screen in red and can be transferred to a PC. In addition, up to ten user settings can be saved to non-volatile memory and recalled later. The current settings are automatically saved three seconds after they are changed which ensures that the oscilloscope starts in the same mode next time you power it up. If you have many unwanted settings, you can always press the DEFAULT SETUP button and begin with the most common options. Connections The ADS7062CA has a USB device port and a standard GPIB port, both on the rear panel, to enable you to connect the scope to a PC. There is no USB host port, meaning that acquiring screenshots is only possible by connecting to a PC. This could be a problem if you are working in the field or away from a computer. The only way to save waveforms in that case would be to store them on the scope’s internal memory and transfer them later. Screen grabs can be saved with the supplied EasyScope software. Keep in mind that the resolution of the exported bit maps will only be quarter-VGA (320x240 pixels) which is the native resolution of the oscilloscope. You can also export data in CSV (comma separated values) format for importing into a spreadsheet. Conclusion This oscilloscope represents very good value for money. It is reasonably fast and responsive and has many features found only in more expensive oscilloscopes. The colour screen makes this DSO particularly attractive for its price. The biggest compromises are the limited resolution of the screen, limited memory depth (4K) and 8-bit vertical resolution. On the positive side, the scope is supplied with two probes, a USB cable, user manual and PC software. Where from, how much? Recommend retail price is $1195 excluding GST. It can be purchased from Trio Smartcal. For more information, contact: Trio Smartcal or visit www.triosmartcal.com.au SC siliconchip.com.au February 2008  19