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Test Equipment Review Handyscope: a spectrum analyser, scope & multimeter all in one If you’re looking for a low-cost entry into PC-based test equipment, then you should have a look at the Handyscope. It contains a 2-channel oscilloscope, a digital multimeter & a spectrum analyser with a frequency response from DC to 50kHz. By DARREN YATES There’s been quite a bit of noise made over the last year or so about PCbased test equipment and if you look through the engineering magazines, you’ll find that the number of plug-in cards is on the increase. Some of them claim to be able to re­place dedicated instruments although, as you might expect, if you want top performance, you’ll pay a lot of money. But when we recently saw the Handyscope in action, we were quite surprised by its performance. It doesn’t claim to beat specialised test gear but it’s extremely flexible at what it can do – and that’s quite a bit! The Handyscope originates from TiePie Engineering in Hol­ land, is distributed in Australia by Applied Electro Systems from Queensland and is available in either single or two-channel form. The first thing we noticed was that there is no plug-in card and this is great – you don’t need to open up your computer and look for a slot. In fact, it comes in a small box measuring 145 x 84 x 37mm, with a nice long cable at the rear which con­ nects to your printer port. If you have more than one port, you can connect your print­er to one and the Handyscope to the other. It doesn’t matter which goes where because the software automatically searches for the Handyscope itself. One intriguing thing we noticed was that there are no power supply cables for the Handyscope. Many of you may know that the printer port doesn’t have any supply rails on the pins, so the question is where do they get power from? The clever trick used is that they have set five of the data output lines of the printer port high and then pull 4mA out of each line. Because the outputs are TTL, this is quite OK and inside the Handyscope box is a step-up converter which converts this supply into ±5V DC. Specifications The Handyscope uses a 12-bit A/D converter which has a conversion time of 10µs, giving a sampling frequency of 100kHz and a maximum possible Left: the 2-channel digital voltmeter measures AC & DC voltag­es with true RMS values. Other modes offered are peak-to-peak, mean value, min-max, power, dBms & frequency. DC voltages are read automatically if DC coupling is selected by the switch on the front of the box. September 1993  53 Initially, it comes up in oscilloscope mode and it produces a normal scope display with graticule and trace. But there are lots of other little tricks. If you connect a signal to the input, you’ll see it appear on the screen but the interesting thing is that if you wind the signal amplitude up or down, the volts/div will follow it by auto-scaling to give an optimum display on the screen. The timebase ranges from 0.5ms/div to 2 seconds/div with the option to magnify this up to 20 times. (If running on an XT, the 0.5 and 1ms/ div ranges are not available). The accuracy of the timebase is only fair at ±5% but this is adequate for many applications. The Y-axis can also be changed to either linear or dB modes. All the usual scope features are available, including trig­ ger settings for channel and slope. You can also select the hysteresis level for the triggering as well. If you have the two-channel model, you can add or subtract one waveform from another. You can also zoom in on one part of the screen waveform and examine it in expanded format. Spectrum analyser The Handyscope hooks up to your PC & uses the monitor as the readout. It contains a 2-channel oscilloscope, a digital multimeter & a spectrum analyser with a frequency response from DC to 50kHz. input frequency of 50kHz. The 12 bits give a maximum resolution of about 0.025% (ie, 1/4096=LSB). Linearity is good to 10 bits over a frequency range of DC to 50kHz. The input impedance of each channel is 1MΩ with 20pF ca­pacitance, which is the same as for standard oscilloscopes. Two switchable 1:1/10:1 probes are supplied. Software As with all PC-based equipment, there’s software to consid­er as well. And in this case, it’s quite well done. The software comes on single 3.5-inch and 5.25-inch discs for both drive types. There’s no installation procedure – you can either run the pro­gram straight from the floppy or copy the disc’s contents to a directory on your hard disc drive. The program isn’t all that big either –you’ll need only about 350Kb of disc 54  Silicon Chip space to copy everything over. The good news is that it runs in DOS so you don’t have to slow it down by running it in Windows. However, if you wish to take some screen snapshots, you can run Windows in the background and when you have the shot on the screen you want, you just type [ALT][PRINT SCREEN] and the screen will be copied to the Windows clipboard. As far as I’m concerned, this gives the best of both worlds. In fact, the screen shots shown in this article were produced by this method. To start the Handyscope, you plug the cable into the print­ er port and then type HS[enter]. The program then looks and announces that it has found the Handyscope on whatever printer port you’ve connected it to. You can then select all modes and settings using your mouse which makes it quite attractive to use. The spectrum analyser is a very handy tool and is quite speedy on a 386DX-40 considering the number of computations it must do. You can select to average over a choice of samples from 1 to 200 as well as changing the frequency response and volt/div settings of the screen. Another good point is that the Handyscope system even runs on an old XT and although the spectrum analyser mode works up to 36kHz on an AT, it only goes to 12kHz on an XT. There are 12 ranges covering the frequency band of 0.025Hz to 36kHz for ATs and above and 10 covering 0.025Hz to 12kHz for XTs. You can multiply these ranges up to a maximum of 20 times as well for a more detailed view of the display. The analyser uses the Fast-Fourier-transform (FFT) method and takes 1024 samples. From these samples, it produces 512 spectral components which are then displayed on the screen. It also has the ability to calculate total harmonic distor­tion based on the fundamental frequency you select by dragging the crosshairs on the screen to any spectral line you wish. It pro- Since the Handyscope works as an AC multimeter, you can make more accurate measurements by centring the frequency. For example, by setting the centre frequency to 50Hz, signals with frequency components from 10Hz to 500Hz will be correctly calcu­lated. The maximum input voltage is 200V peak-to-peak and 600Vpp with the probe set to 1:10. Transient recorder The spectrum analyser is a very handy tool. You can select to average over a choice of samples from 1-200 & you can change the frequency response & volt/ div settings. There are 12 ranges covering the frequency band of 0.025Hz to 36kHz for ATs & 10 ranges covering 0.025Hz to 12kHz for XTs. The transient recorder can be used to measure a system over long periods. The time between measurements can be set from 0.01 seconds up to 300 seconds, while the maximum number of readings taken is 30,000. Measuring methods using this recorder can be true RMS, mean, minimum, maximum or momentary pulses. The unit comes with a comprehensive instruction manual, which includes details on the pinouts for the printer port as well as data output format. This is to allow users to write their own software to control the Handyscope. Example code is given in the manual for TurboPascal but by following the layout and form of the code, it can be easily translated into QuickBASIC. Disc operation All the usual scope features are available, including trig­ger settings for channel & slope. You can also select the hysteresis level for the triggering & if you have the 2-channel model, you can add or subtract one waveform from another. vides a reading of the amplitude of the fundamental frequency as well as that of the first 10 harmonics and then the THD in decibels (dB). Digital voltmeter The digital voltmeter measures AC and DC voltag­es with true RMS values. Other modes offered are peak-to-peak, mean value, min-max, power, dBms and frequency. You can even set the thickness of the digit displays as well. DC voltages are read automatically once DC coupling is selected by the switch on the front of the box. You can also operate it as a comparator by setting an input reference level and if the signal is higher or lower, the display indicates HI or LO approp­ riately. Alternatively, you can use this feature to compare one channel against another. As you would expect, you can save any waveforms to disc for storage and later retrieval or you can print the screen to a printer. You can use either the method we mentioned earlier or you can print direct to the printer using a spare printer port. The printout can be in either dot matrix or laser form. Each set of data is stored in two separate files: the data is stored in filename.DAT, while the settings of the instrument are stored in file­name. GEG. Overall, the Handyscope is a well thought out unit. It may not be ideal if you’re looking for extremely accurate results but for schools and TAFE colleges where you need to be able to display waveforms quickly and easily, this will be an ideal and a relatively low-cost addition. The two-channel model sells for $960 ex tax and the single channel version for $550 ex tax. For more details, contact Ap­plied Electro Systems Pty Ltd, PO Box 319, Woodridge, Qld SC 4114. Phone (07) 208 6911. September 1993  55