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Speaking from experience, I know that troubleshooting electrical/electronic equipment in the field can be a real pain in the proverbial. Lugging large, supposedly “portable” and usually expensive pieces of test equipment around the country can really test the nerves – as well as the muscles. Could this be the answer? TiePie HANDYPROBE HP2 Review by PETER SMITH T HE HIGH COST of portable test equipment also means that many companies cannot afford to outfit each engineer with his or her own gear. If you have a problem in Sydney but the gear’s in Perth, too bad – the problem has to wait and the customer might not be understanding... TiePie Engineering, a Dutch company which specialises in computer controlled measuring equipment, has come up with a unique solution to this field service dilemma in the Handyprobe 2. The Handyprobe 2 incorporates a storage oscilloscope, spectrum analyser, voltmeter and transient recorder all in a package that fits in the palm of your hand! The probe plugs into the parallel port of any PC and in conjunction with DOS or Windows software provides a comprehensive range of data acquisition functions. It is powered directly from the parallel port connection (no external supply or batteries are required) so is ideally suited for use with laptop computers. In fact, the probe together with its integral cable could easily TiePie engineering slide into a spare spot in most laptop bags. With an input range of 0.5V to 400V full scale and a maximum sampling speed of 20MHz (TiePie also produce 1,2,5 and 10MHz versions), the Handyprobe can handle just about anything you can throw at it. Here are just a few “typical” applications suggested by TiePie: serial data communications, TV signals, power inverters, industrial production machines, office equipment, sensor readings (eg, temperature, pressure and humidity), line measurements, inrush currents, line distortion, sound and vibration analysis, trend measurements, and once-only disturbance detection measurements. Instrument settings can be saved and restored from disk at will, saving time on-site and perhaps reducing the required level of operator training. To keep the cost down, TiePie have provided only single-channel acquisition in the Handyprobe 2. As with most storage ‘scopes, the Handyprobe includes a reference channel that can be used to compare a stored measurement with a second (live) measurement, so a second channel is usually not required. As mentioned above, the Handyprobe 2 software runs under both DOS and Windows. PC hardware requirements are minimal - the basic DOS version will run on an 80286 or even 8088-based (IBM-XT) PC. The Windows version requires a 486DX2-66 or faster processor with at least 8MB of RAM. TiePie recently released 32-bit versions of their software for Windows 95/98 and Windows NT and this is what we used for our review. Walking the dog The newer 32-bit software wasn’t supplied with our review package, so we downloaded it from TiePie’s web site at www.tiepie.nl Installation was a piece of cake and took about five minutes. An additional driver is required if you’re running Windows NT 4 (or JUNE 2000  77 It’s not quite plug’n’play – it’s plug’n’work! The TiePie Handyprobe HP2 is definitely all business . . . but it’s a pleasure to use. Shown here are the instrument itself, software and instruction manuals. Windows 2000) and this can also be downloaded from the same site. Launching the Handyprobe 2 software displays a floating toolbar on the Windows desktop (see Fig.1). The toolbar provides access to all four of the available instruments, as well as to basic program settings (see Fig.2). The ’scope, voltmeter and spectrum analyser instruments can all be active simultaneously, whereas the transient recorder must run independently. Let’s take a look at each of the instruments and their capabilities in a little detail. Note that we’ve provided more detail on the oscilloscope and voltmeter instruments, as these will likely be of most interest to our readers. Storage oscilloscope TiePie boast that their instruments are “plug and measure”. This is, of course, one of the benefits of a totally software-controlled instrument, and we were keen to try it out. We connected the probe to our trusty Silicon Chip Sine/Square Wave Generator, activated the oscilloscope and hit the Auto SET button. In less than a second the input was scaled nicely (both horizontally and vertically) and correctly triggered (see Fig.3). Auto SET places the instrument in auto-ranging mode, so for many simple measurements you may not need to do any setup at all. All instrument settings are available from the main toolbar via pulldown menus, with many often-used settings also controllable with single-keystroke shortcuts. Vertical axis The CH1 pull-down menu provides access to all vertical axis settings. Input sensitivity ranges from 0.5V to 400V full scale, configurable from the Sensitivity selection (see Fig.4). A l t e r n a t i v e l y, hitting the F5/F6 keys clicks over Fig.1: the instrument toolbar provides a convenient way of activating the instruments. All except the transient recorder can be active simultaneously. 78  Silicon Chip to the next lowest/highest setting - a bit like using that rotary switch on CRT-based oscilloscopes. Measured values can be enlarged or reduced using the “Software Gain” function – TiePie calls this vertical axis magnification. A closely related function called “Software Offset” applies a positive or negative bias to the vertical axis. Once again I was reminded of the conventional ‘scope and the equivalent “position” knob (got to kick that habit). Both the Software Gain and Offset can also be changed directly on the display by clicking and dragging points on the vertical axis – great Fig.2: settings common to all instruments are accessible from the toolbar. Although not mentioned in the text, instrument calibration data can be defined on the Hardware tab. Fig.3: the “oscilloscope”. Comment balloons provide an easy way of annotating waveforms before printing. feature! The Units of measure, Units of gain and Units of offset functions provide for custom vertical axis marking and scaling, making tailoring for specific measuring tasks quite simple. For example, suppose you have a temperature probe whose output changes by 1V for every 10 degrees of temperature change. By setting the Units of measure to “Degrees C” and Units of gain to “10”, the vertical axis displays temperature change directly in degrees. Other options on this menu allow choices of true or inverted signal, and either AC or DC signal coupling. Horizontal axis Unlike its more conventional analog cousin, the digital scope’s timebase is dependant on both the rate at which the incoming signal is sampled and how many samples are stored and subsequently displayed across the horizontal axis. The Handyprobe 2 has a maximum sampling rate of 20 million samples/ second and a memory depth (also called record length) of 32,760. Both the sample rate and record length are configurable from the Timebase pulldown menu (see Fig.5). Naturally, the Handyprobe software automatically adjusts the time/ div values along the horizontal axis when the sample rate and record length are changed. Also accessible from the Timebase menu are two options that allow closer examination of any part of the acquired signal. Record View Gain provides horizontal axis magnification, whereas Record View Offset allows display of a particular section Fig.4: manually setting the input range. of the record. Note the scroll bar directly below the horizontal axis – this provides a much more convenient way of panning through the record than manually entering the Record View Offset. After fiddling with the software gains and offsets for a while to get my test signals to look the way I wanted, I started to wish there were an easier way – and there is! A “zoom” button on the toolbar allows you to select a region of the display that you would like to examine, and the correct gains and offsets are automatically applied to both the horizontal and vertical axes to make it all happen. A feature in digital ‘scopes that I’ve often found useful is their ability to display a number of samples prior to triggering. On the Handyprobe, the number of pre-trigger samples can be set an- Table 1: TiePie Handyprobe 2 Hardware Specifications Input channels 1 analog A/D converter: resolution conversion time effective data throughput 8 bits, 0.39% 50ns 1M, 2M, 5M, 10M or 20 Mega samples/sec    (depending on model) Analog input: sensitivity maximum voltage impedance coupling accuracy bandwidth 0.5V to 400V full scale 500V 1MΩ / 30pF AC/DC 1% ± 1 LSB DC to 2MHz Trigger system: level adjustment resolution pre-trigger post-trigger 0 - 100% of full scale 0.39%, 8 bits 0 - 32768 samples (0 - 100%) 0 - 32768 samples (0 - 100%) Maximum sample rate 1, 2, 5, 10 or 20M samples/sec (depending on model) Memory 64K words Interface PC-compatible parallel port (LPT1, 2 or 3) Cable length 1.8m Power Derived from LPT port Dimensions 22 x 125 x 43mm (H x L x W) Weight 260 grams JUNE 2000  79 Fig.5: selecting the sample frequency (or rate) from the Time base menu. The faster the sample rate, the less time it takes to fill an entire record. As shown here, at 10kS/sec the record is filled in just 100ms. ywhere from zero to the maximum record size. A second scroll bar at the bottom of the display allows this value to be changed instantly. Triggering As expected, the Handyprobe includes variable level triggering on a rising or falling slope. Slope position, level and hysteresis can all be set from the Trigger pull-down menu. Easier still, these values can be changed by clicking and dragging the trigger symbol next to the vertical axis - too easy! Auto level triggering is also selectable; when active an “A” is visible next to the trigger symbol. Noisy signals and glitches Noisy signals can be “cleaned up” by using Handyprobe’s signal averaging feature. A number of user-definable samples (4 - 256) is taken and the results are averaged, removing unwanted noise. Spotting a glitch on a real-time display is often impossible - but TiePie have the bases covered here, too. Envelope mode keeps a record of the highest and lowest samples since last reset and compares these values to each successive sample. When a sample that exceeds either of these limits is detected, a vertical line is drawn on the display at that point and the value is stored as the new lowest (or highest). Envelope mode can be reset at any user-definable measurement interval – or it can run indefinitely. you want for a particular measuring task, you can save those settings to disk for later reuse. And there is no limit to the number of settings files you can create, either. Another indispensable feature allows waveforms (both live and reference channels) to be saved on disk for later examination. This would also be handy for record keeping or documentation, especially when combined with the hardcopy feature (see below). Data files can be saved either in binary or ASCII format, allowing further processing by other applications. Waveforms can also be saved to disk automatically using the Auto Disk feature. This feature copies the Fig.6: movable cursors provide detailed measurement information. The cursors can even be set to automatically find zero crossing points. contents of live memory to disk after each complete record acquisition. With careful setup of the trigger system, this feature could be used to wait for and capture unusual signal excursions, such as the dreaded glitch! A limitation with the naming of Auto Disk files allows a maximum of only 999 files to be created in a single session (the last three digits of filenames are automatically assigned numbers 1 - 999). This is not a problem for most applications but seems an unnecessary limitation nevertheless. Accurate measurements A variety of useful measurements can be made quickly and easily by using mouse-moveable cursors. These are enabled from the Cursors pull-down menu and once enabled, a dialog box appears, listing all the Saving settings & waveforms The good news is that once you’ve got the instruments set up the way 80  Silicon Chip Fig.7: comparing a previously acquired signal (shown in red) with a live signal. If desired, the reference signal can be automatically scaled to match the live signal. Fig.8: example hardcopy output. We sent our output to a Postscript file rather than a real printer, allowing us to import it into just about any application. measurements made at the current cursor positions (see Fig.6) Reference memory OK, so we said that the record length (memory depth) is 32K, but the specs table (see Table 1) lists 64K – where’d the other half go? As we mentioned earlier, digital ‘scopes usually contain reference memory - an area of memory that is used to temporarily store a copy of live memory for comparative purposes. Clicking the “Copy to Ref” button on the toolbar transfers a copy of the current live memory contents to Fig.9: the voltmeter alone could make the TiePie Handyprobe an indispensable instrument for all service personnel. reference memory (also called the reference channel). Clicking on the “Ref1” button displays the reference channel (see Fig.7) along with the current live channel, if active. shape and colour are customisable, too. As shown in our example, a longer (up to 3 line) comment can also be added to the top right of the printout. Hard copy As with all the other instruments in the package, TiePie have done their best to make the voltmeter as functional as possible. Data is presented to the user in a similar manner to a conventional digital voltmeter (DVM), and includes triple displays with bargraphs (see Fig.9). The input signal can be either AC or DC coupled, with a range of between 0.5 and 400V full scale. Autoranging is also supported. Each display is independently configurable via the Settings pull-down menu. Measurements can be made in true RMS, peak-to-peak, mean, maximum, minimum, dBm, power, crest, frequency, duty cycle or moment value (see Fig.10). Amps, Kilograms, Degrees C and Watts are just a sample of the various Units of measure that can be selected to ease the strain on the grey matter. And of course, displayed values can be scaled to suit by changing the Units per measurement unit value. Quick “go-no go” tests can be made by configuring the Set high value and Set low value entries appropriately. This function is also useful for monitoring a signal for out-of-range conditions, depending on how the sound settings (see Fig.11) are configured. To reduce the obvious duplication of settings between instruments, Tie- A faithful copy of the displayed waveform can be made at any time by using the Print feature (see Fig.8). Comments can be added anywhere on the display area with the aid of user-definable comment balloons. Balloons can have arrows that point wherever you like (see our “Clipping” balloon example on Fig.3). Balloon Fig.10: all three of the voltmeter displays are independently configurable. And you can store all your favourite settings on disk. Voltmeter JUNE 2000  81 Fig.12: Measurements can be made at intervals of between 1 and 300 seconds, with the results stored on disk or sent to the printer. Fig.11: testing between limits is made easier with audible feedback. Here we can set the actual tones used and select either PC speaker or sound card as the playback device. Pie have slaved many of the settings together. For example, the voltmeter actually uses the record length and post-trigger samples from the oscilloscope. If either the oscilloscope or spectrum analyser is active though, their settings override the voltmeter settings as the voltmeter has lowest priority. The frequency range setting is an exception to this rule, as changing it in the voltmeter affects all other instruments. TiePie have included a “use scope frequency” setting to avoid potential frustration! The voltmeter takes 200 samples of the input signal at the selected frequency range for each measurement. Without going into any detail, we note that the selected range is critical to obtaining an accurate measurement. An Auto frequency option has been included on the Settings menu that eliminates the guesswork. In common with all other instru- ments, the voltmeter can be set to either measure continuously or perform one-shot measurements at the press of a button. An addition recording function on this instrument allows measurements to be made at intervals of between 1 and 300 seconds, with the results stored on disk. This function is configured from the Acquisition pull-down menu (see Fig.12). Spectrum analyser If you work with filters, amplifiers, oscillators, mixers, modulators, or detectors, you need a spectrum analyser. Whereas oscilloscopes display signals in the time domain (which is fine for determining amplitude, time and phase information) spectrum analysers display signals in the frequency domain. The frequency domain contains certain information that is just not Fig.13: the spectrum analyser instrument really expands the usefulness of the package. 82  Silicon Chip visible in the time domain. To borrow several examples from the Handyprobe user manual: 1. A sine wave may look good in the time domain, but in the frequency domain harmonic distortion is visible. 2. A noise signal may look totally random in the time domain, but in the frequency domain one frequency may be dominantly present. 3. In the frequency domain it is easy to determine carrier frequency, modulation frequency, modulation level and modulation distortion from an AM or FM signal. Fig.13 shows what a 200kHz square wave looks like on the spectrum analyser. Square waves are (theoretically) composed of an infinite number of harmonics, some of which you can see on the left and right of the 200kHz peak. Without going into complicated explanations, suffice to say that the Handyprobe software uses Fast Fourier Transforms (FFT) to calculate the spectral components of the sampled signal. Errors are introduced during this conversion process, and by using one of several FFT windowing techniques selectable from the Settings pull- Fig.14: TiePie have included important window functions for the spectrum analyser. Fig.15: Don’t like the type of horizontal axis offered? Change it! down menu these can be reduced to a minimum (see Fig.14). Vertical axis With two exceptions, all vertical axis settings are the same as on the oscilloscope instrument. In fact, key settings such as sensitivity and triggering are slaved between instruments to make setup a little easier. Of course, they can also be individually controlled if necessary. The spectrum analyser instrument adds an option for either a linear (volts) or logarithmic (decibels) vertical axis scale, and removes the Units of measure option. Horizontal axis The frequency axis pull-down menu provides access to all horizontal axis settings. In a similar manner to the oscilloscope, both the sampling frequency and record length can be set here. Also of interest is the Axis Type setting (see Fig.15). Measuring harmonics An important feature of this instrument is its ability to measure Total Harmonic Distortion (THD). This is set up and displayed from the Measure pull-down menu. The number of harmonics used to calculate the THD is user definable and the results can be displayed in decibels or as a percentage (see Fig.16). As with the oscilloscope, cursors are provided for easy waveform measurement (see Fig.17). A multitude of other features match those that we have already described for the oscilloscope in- Fig.16: to measure THD, simply set the number of strument. These in- harmonics to use in the calculations and hit the “go” lude display zoom- button. ing, signal averaging, copying live to used also mean that other instruments reference memory, saving waveforms cannot be active when the transient to disk, hardcopy output and saving/ recorder is active. restoring instrument settings. Many features of this instrument are common to those found on the Transient recorder oscilloscope and spectrum analyser, If you need to measure slowly so we’ll concentrate mainly on the changing signals over a period of unique ones here. time, the transient recorder is the Recording speed instrument of choice (see Fig.18). Unlike the other instruments in Sampling time can be set anywhere the package, the transient recorder from 0.01 second to 500 seconds (see is direct registering. This means that Fig.19), with a complete record variait displays each measurement as it ble from 1 to 32,760 samples. is made, rather than waiting for an The recording process can be inentire record to be acquired. This terrupted at any time and the results is necessary because at the lowest saved to disk or printed. It is also sample rate, it can take up to 189.6 possible to have the recorder run days to fill a record! The different measurement and display techniques Fig.17: once again, the cursor readout makes measurements easy. Fig.18: the transient recorder instrument. Here we’ve used the Units of measure and Units of gain settings to simulate a thermocouple reading in thousands of °C. JUNE 2000  83 an arbitrary waveform generator (AWG) instrument. Software for the TiePieSCOPE is practically identical to the Handyprobe, notwithstanding the additional support for the second channel and the AWG. We’ve included a screen shot of the AWG just to wet your appetite (see Fig.20)! Where to get more information – and it! Fig.19: setting the transient recorder measure speed. continuously and automatically save to disk at the end of each complete record acquisition. Note that at very high measuring speeds, TiePie state that some data samples may be lost due to the overhead of disk access. During recording, the display can be set to roll left as the trace reaches the rightmost edge of the screen – a great feature that reminds me of mechanical chart recorders with their drums and pens. Data gathered from the recorder will most often be used for documentation purposes, so the vertical axis custom­isation features really shine in this instrument. Pre-defined choices for the units of measure include Volt, Amp, Degree C, Degree F, Watt, Percent, Meter, Kilogram, Newton, Coulomb, Bar and Hertz. If you can’t find what you want in that lot you can define your own in five characters or less. Text balloons of variable shape, size and colour can be positioned anywhere on the display, and colour printer output is supported, too! A sample rate of at least 10 times the signal frequency is widely accepted as the minimum that is required to provide reasonable signal reconstruction, which means that the useable bandwidth of the oscilloscope and spectrum analyser (for the 20M samples/sec version) is around 2MHz under most conditions. Need more speed? If the Handyprobe 2 sounds great but you need more bandwidth or another channel, TiePie also offer the TiePieSCOPE HS801. This instrument is not quite as portable as the Handyprobe, but it adds a second channel, has five times the sample rate (100M samples/sec) and includes Hardware specifications Table 1 lists the key Handyprobe 2 hardware specifications. The input resolution is listed as 8 bits, 0.39%, with an accuracy of 1% ± 1 LSB. The sample rate used to measure any signal must be at least twice its frequency to prevent false readings (called “aliasing”). This rule applies to all the instruments except the transient recorder. 84  Silicon Chip Fig.20: here’s a glimpse of the TiePie HandyProbe’s “big brother”, the $2450 HandyScope and (inset) its arbitrary waveform generator. Self-running demos and complete user manuals for the Handyprobe 2 and TiePieSCOPE are available for free download from Tiepie’s web site at www.tiepie.nl. Our review unit came from the Australian distributors of TiePie Engineering products,Melbourne-based RTN, phone/fax (03) 9338 3306; email nollet<at>enternet.com.au. Pricing The 10MHz TiePie HP2 (as reviewed) currently has a recommended price of $740 including sales tax. A 20MHz version sells for $810. Note that these prices are almost certain to change next month with the introduction of the GST but also due to currency fluctuations. Current prices are based on $AU1=$US0.6 but at press time the Aussie dollar had fallen below that rate and the chances are it will go lower. A phone call to RTN will give you the latest pricing. The TiePie HP2 carries a 12 month warranty and most servicing is carSC ried out locally.