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PRODUCT SHOWCASE A handheld LCD oscilloscope There have been a number of handheld multimeter/oscillo­scope instruments produced in the last few years but most of them have been priced well above what the average technician or hobby­ ist could afford. This new unit made by Velleman is much more affordable. All told, this new instrument has a surprising number of features packed into its compact 600 gram (excluding batteries) package. The case dimensions of 230 x 130 x 43mm allow it to be comfortably held in the average hand. When fitted with six AA rechargeable batteries it will operate for up to five hours or it can be powered from an external 9V DC 300mA plugpack. Its full specifications are listed in Table 1. The unit boasts a full auto setup function which means that any signal can be connected and immediately a stable waveform is displayed. Not only this but the period and frequency of the input can be read from the righthand side of the LCD panel. As well, the meter function button can select one additional read­out, either of the waveform’s peak-to-peak voltage, RMS voltage, signal level in dB or DC voltage. While the waveform display area itself is rather tiny (50 x 40mm) it gives a good portrayal of most waveforms. All functions are controlled by membrane switches on the front panel and these are more or less self-explanatory for anyone who has used an oscilloscope previously. A red pushbutton labelled Markers switches four different backgrounds on the display. The first is a plain background, the second provides a dot grid with 5mm spacing which, on the dis­play, is 9 dots across by 8 dots high. The third provides cen­trally lo- cated X and Y axes and the last has two pairs of cursors which can be moved to make peakto-peak voltage and period meas­urements. The Y position buttons move one of the P/P cursors while the trigger level buttons move the other. By positioning them at the maximum and minimum of any waveform the peak- to-peak value can be read. Similarly, by using the Time/div and Trigger mode buttons, the period between any two points on the waveform can be measured. Getting back to the oscilloscope functions, the BNC input has an impedance of 1MΩ and 25pF which is similar to many oscil­loscopes. A small slide switch below the BNC connector lets you select AC or DC coupling for the input signal and the input sensitivity is controlled by the adjacent Volt/div pushbuttons. To increase the sensitivity of the input amplifier you push the button with the big sinewave on it, while pushing the button with the small sinewave reduces the sensitivity. Below the input buttons is the normal on/off pushbutton. If this is used to turn the unit on it will turn itself off about eight minutes after the last keypress. If this is not convenient, the unit can be turned on permanently by using the Markers key. If the scope is to be operated manually (as distinct from the auto setup mode) then the Time/div buttons operate like a normal scope, with the Trigger mode buttons allowing normal, auto or single sweep operation. Another button toggles the trigger from positive edge to negative edge, with the two buttons above it letting you move the trigger point amplitude up and down. The only controls we still have to mention are the Y posi­tion, Dot/Join and Hold buttons. The Y position controls only operate in manual mode because, as we explained previously, in Auto mode they move the cursor. The Dot/join button does just that. It allows the display to show the digitised values as dots, or in the join mode it connects all the points, displaying July 1997  75 Table 1. Technical Data Maximum sample rate ������������������������ 5MHz for repetitive signals; 0.5 MHz for single shot signals Input amplifier bandwidth ������������������� 750kHz (-3dB at 0.4V/div setting) Input impedance ��������������������������������� 1MW // 20pF Maximum input voltage ���������������������� 100V peak (AC+DC) 600V with 10x probe Input coupling ������������������������������������� DC, AC or ground Vertical resolution ������������������������������� 8 bit (6 bit on LCD) Linearity ���������������������������������������������� ±1 bit A/D converter accuracy ���������������������� ±2 bit LCD graphics ������������������������������������� 64 x 128 pixels, 64 x 96 for signals dB measurement (0dB = 0.775V) �������� from -73 to +40 ±0.5% True RMS range (AC only) ������������������ 0.1mV to 80V, 2.5% accuracy Peak-to-peak and DC range ����������������� 0.1mV to 180V, 2% accuracy Timebase range ����������������������������������� 20s, 10s, 5s, 2s, 1s – 10ms, 4ms, 2ms/div Input sensitivity ����������������������������������� 5mV, 10mV, 20mV, 50mV, 100mV – 2V, 4V, 8V, 20V Sinewave generator ����������������������������� 400Hz 1V RMS max (adjustable) Square-wave output ���������������������������� 400Hz 3.5V p-p Plugpack voltage ��������������������������������� 9V DC 300mA Rechargeable batteries (opt.) �������������� 6 AA, 750 or 900mAh Charge time ����������������������������������������� 14 hours Battery operation �������������������������������� 5 hours (900mAh) Operating temperature ������������������������ 0-50°C Dimensions ����������������������������������������� 230 x 130 x 43mm Weight ������������������������������������������������ 600 grams (excludes batteries) This series of screen shots show a number of operating features of the Velleman HHS5 handheld scope. The top screen shows a waveform bracketed by vertical and horizontal cursors for peak to peak & frequency measurements. The second screen shows a sinewave with a true RMS readout. The trigger level is indicated by a break in the lefthand vertical axis line. A dot grid is also displayed. The third screen shows a square wave with peak-to-peak readout and centrally located horizontal & vertical axes. The fourth screen shows a sinewave in “dot join” mode while the fifth screen shows the same waveform in “dot” mode. 76  Silicon Chip the conven­tional continuous trace we are more familiar with. The Hold control freezes the display, allowing you to exam­ine any particular aspect of the waveform. As well, it lets you send a digitised data stream of the displayed signal to the RS232 port on a computer. The information is sent as a table of 96 samples, each having a value between 0 and 255 as well as the Y sensitivity and the zero reference value. This information could be used by a spreadsheet or Basic program to process the details of the display in any required manner. One unusual but welcome feature of this instrument is the inclusion of a circuit diagram and PC board parts overlay in the back of the manual. Our only complaint was that the righthand edge of the LCD display was covered by the front panel mask and we could not read the last digit of the readout. We could also see the left­hand silver edge of the LCD surround but not the righthand one. When we opened the case we found that the perspex mask was held in by two pieces of sticky tape. Removing this mask, rotating it 180° and replacing it cured the problem completely. Perhaps the only real drawback of this scope is the limited bandwidth of 750kHz. Having said that, it is true that the major­ ity of measurements that need to be made in most situations are normally well below this frequency. On the positive side, the advantages of true RMS measure­ments and auto setup along with all the other features make this unit an attractive purchase for the technician or hobby­ist. The recommended retail price of the unit is $449 and it is available from all Jaycar Electronics stores. (R.J.W.) AUDIO MODULES Fast slewing operational amplifier Analog Devices has introduced the industry’s fastest slew­ing monolithic operational amplifier. The current feedback AD8009 features a 5500V/µs slew rate, more than twice that of its near­est equivalent, with 10% faster rise and fall times at 725ps for a 4V step. As a simple gain stage or buffer amplifier in high frequen­cy instrumentation or in high speed test gear (as a pulse ampli­fier where a combination of high slew rate and low distortion is needed to inject signals of high integrity), the AD­ 8009 outperforms all other devices. Small signal (-3dB) bandwidth is 1GHz at unity gain and 700MHz with a gain of +2. Dynamic performance is excellent: spurious free dynamic range is 74dBc at 5MHz, 53dBc at 70MHz, and 44dBc at 150MHz. For mul- broadcast quality ti-tone signals, such as RF/IF signals, the 3rd order intercept is specified at 26dBm at 70MHz and 18dBm at 150MHz. Settling time to within 0.1% of full scale signals is 10ns. For further information, contact Hartec, 205A Middleborough Rd, Box Hill, Vic 3128. Phone 1 800 335 623. 25W external power supply Today’s electronic equipment can encounter a myriad of approvals and assessment before it can be put on the market. Usually the two main hurdles are safety and EMI. Amtex Electron­ ics have attempted to overcome the majority of these by introduc­ing the SCL25 series of external switching power supplies. The SCL25 series are fully approved, carrying local office of energy and Austel approvals, and soon to carry the new C-Tick mark. As well, they carry international approval, such as UL, CSA and VDE for safety, as well as FCC and CE for EMI noise. The SCL25 series come in a sturdy moulded plastic case. The input is 90264VAC via an IEC input socket and single output voltages ranging from 5VDC to 48VDC are available, as well as dual and triple output units of 5V and ±12V or ±15VDC. Output is via an 8-pin mini-DIN or 2.5mm jack plug. The units also feature an output LED indicator, regulation of ±4% and up to 60ms hold up time. For further information, contact Amtex Electronics, Power Supply Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 The two diodes may also be connected to operate in parallel due to their matched on-state voltage drops. The modules have an isolation voltage rating of 3000V (RMS) and are UL recognised. Major applications for these diode modules include rectify­ ing the AC output from high-frequency inverters. For further information, contact GEC Electronics Division, Unit 1, 38 South St, Rydalmere, NSW 2116. Phone (02) 9638 1888; fax (02) 9638 1798. Rugged 600V IGBT Division, 2A Angas St, Meadowbank, NSW 2114. Phone (02) 9809 5022; fax (02) 9809 5077. 1200V fast recovery diode modules IXYS Corporation has announced the availability of the MEK 75-12DA fast recovery diode module in the industrial standard TO-240 package. It consists of two matched, 1200V rated, 75A(avg), fast diodes with common cathode connection. The two epitaxial diodes have low reverse recovery current and short reverse recovery time (trr = 450ns maximum at TJ = 100°C) and they exhibit soft reverse voltage recovery to minimise EMI. BBS Electronics has released rugged versions of Harris Semiconductors’ ultrafast switching IGBTs rated at 600V and 20A at 110°C. These new devices allow motor-controller de­ signers to replace power transistors with IGBTs to maximise efficiency (due to IGBTs’ lower conduction losses), without rede­ signing their present short-circuit protection circuits. This series of devices has a short-circuit withstand time of 10µs, the maximum for any IGBT, at 440V and 150°C. Be­cause Harris rates SCWT at 150°C instead of 125°C, designers can use smaller heatsinks. For further information, contact BBS Electronics Australia Pty Ltd, Unit 24, 5-7 Anella Ave, Castle Hill, NSW 2154. Phone (02) 9894 5244; fax (02) SC 9894 5266. July 1997  77