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Two new 100MHz oscilloscopes from HP Hewlett Packard has done the unthinkable released its latest 100MHz digital sampling oscilloscopes with a host of new features but at a price which directly competes with analog CRT readout scopes. By LEO SIMPSON Until now, digital sampling oscilloscopes have been neither cheap or easy to use. Their controls have been generally quite different from those on conventional analog CROs and their price has usually been a lot higher. Now, with the release of the 54600 series oscilloscopes from Hewlett Packard, all that looks set to change. The immediate difference between these new models and previous models fro m the company is that the con- trol lineup is greatly simplified. Not only that, it bears more than a passing resemblance to the control layout on a conventional analog instrument. For example, there are knobs for vertical attenuators, timebase, trace position and trigger level. None of these knobs have any calibrations though, as their settings are shown in the comprehensive CRT display. The knobs work in exactly the same way as those on any analog CRO and their response is instantaneous. This is quite different from typical digital sampling oscilloscopes (from HP) which have a large number of display modes but which require the user to step through a number of keystrokes and screen menus in order to get the wanted display. Autoscale button The best control feature of the lot is the AUTOSCALE button. This takes all the frustration out of getting a useful signal display on the screen. This can be a time-consuming chore even on analog scopes. On the HP 54600 series, all you have to do is connect the probe to a signal source, push the AUTOSCALE button and the signal is locked on the screen, together with the vertical attenuator and timebase settings. Dead easy. Unlike analog scopes, the new 100MHz scopes display their waveforms brightly and steadily regardless of sweep speed. They do not exhibit the flicker or flare that occurs with analog scopes when displaying signals at very low sweep speeds. Instead, they show a trace of constant brightness, which is gradually retraced, to give the user a visual cue of the low trace speed. Also, the faint traces in highly magnified delayed sweeps can be viewed without the viewing hood required with analog scopes. A peakdetect feature enables the new instruments to display complex waveforms, such as amplitude modulation, correctly. It will catch and display any glitch that is more than 50ns long, regardless of the sweep speed settings. Waveform measurement While it is a digital sampling oscilloscope, HP's 54600 behaves very much like a conventional analog instrument albeit with full CRT readout, electronic graticule and good intuitive "feel". 72 SILICON CHIP The new scopes have the non-volatile storage and waveform-measurement capabilities that only a digital sampling system can provide. With the scopes' two trace memories, signals can be acquired and retained Seen here is the HP54601A, the four channel version of the new 100MHz oscilloscope. It is a very compact instrument with a large screen and easy to use controls. indefinitely. This allows the user to make measurements, compare a previously captured signal with a current one, print hard copies or transfer the data to an external computer for further processing. Pre-trigger viewing Storage also allows pre-trigger viewing by retaining waveform activity that occurs before the trigger event. For example, after triggering the scope on a failure mode in the device under test, a user can look back in time to view the events that caused the failure. This is impossible in an analog scope. AUTOSTORE mode displays the current waveform at full brightness, while all previous sweeps are retained on the display in half-bright, infinite persistence. With this feature, the scope can capture infrequent deviations that otherwise would require constant observation by the user to determine whether deviations occur. The design of the new scopes is based on a new digital architecture developed by HP. Because the instruments use custom IC processors for acquisition and display, they do not rely on the system's CPU to perform acquisition and display management functions. For users , these dedicated processors mean the new scopes have display-update rates as fast as those of analog instruments. Key features of the new oscilloscopes include the following: 100MHz rep.etitive bandwidth on both the vertical and horizontal axes; 2MHz single shot bandwidth; 2ns/ div to 5s/div range on both main and delayed timebases; mV/div to 5V/div vertical sensitivity; 8-bit vertical resolution; automatic setup with a single keystroke; simple one-button display storage operations; 16 front-panel setup memories; two trace memories; edge, line and TV triggering; 12 auto- matic measurements of frequency, time and voltage; dual cursors for accurate manual time and voltage measurements ; pushbutton hardcopy output to plotters and printers via optional parallel, RS-232 or HP-IB (IEEE-488) interfaces. Dimensions are 360mm wide, 180mm high and 300mm deep and weight is 6.4kg. The 54600 series scopes come with a 3-year standard limited warranty with an option for a 5-year limited warranty. Prices are as follows: HP 54600A 2-channel 100MHz oscilloscope, $2,395; HP 54601A 4-channel 100MHz oscilloscope, $2,895; HP 54650A HP-IB interface module, $475; HP 54651A RS-232C interface module , $475; HP 54652A parallel interface module , $275. These prices do not include sales tax. We hope to do a detailed review of the 54600 series in a future issue. In the meantime, sales information can be obtained by calling Hewlett-Packard's customer information centre on (008) 033 821. SC APRIL 1991 73