Color displays make inroads into DSO world

DSO.FEB–WY

Color displays make inroads into DSO world

Digital oscilloscopes with new types of color displays compete with those employing traditional shadow-mask color displays

BY WARREN YATES
Associate Editor

Color offers significant benefits to scope users. It improves the user's measurement efficiency by making the display easier to interpret and the measurements easier to set up. Color also helps reduce the probability of measurement error.
Figure 1 shows just how effective color can be in simplifying a complex and busy display. Here, the behavior of each of four different and overlapping waveforms is clearly distinguishable because each waveform is displayed in a different color. Furthermore, as shown at the bottom of the display, the scale factors associated with each waveform are shown in the same color as the waveform, making it much easier to determine which information on the display is related. Note also that time markers (X1 and X2) are displayed in red, making the markers clearly discernible from the waveforms themselves.
In addition to data association and differentiation, color displays allow users to make qualitative visual measurements that are simply not possible on monochrome displays. For example, some color scopes draw the regions where waveforms overlap in a special overlap color, making it easy to see how the waveforms differ.
While display colors are usually chosen be the scope manufacturer, they can usually be easily changed by the user to meet special needs. For example, colors might be changed to obtain the best display under various ambient light conditions or to accommodate color blindness. Because the colors are adjustable, the display can be configured to minimize eye strain and maximize productivity.
Despite the advantages of color displays, until about a year ago digital oscilloscope (DSO) users had little to choose from in the way of DSOs with color displays. Only a few color DSOs were available and those that were didn't come cheap, costing from about $25,000 to over $50,000. That's because the cost of the traditional shadow-mask color CRT used in the past, along with its associated circuitry and high-power needs, added at least $2,000 to $3,000 to a scope's cost depending on factors like display size and number of scope channels.
Obviously, these additional costs precluded the use of color in low-priced DSOs, and in fact relegated the color displays to use only in the highest-performance–spelled “highest-cost”–DSOs where the additional cost for color could be justified. And even though cost was the major factor limiting the availability of color DSOs in the past, the shadow-mask display's size, bulk, and sensitivity to shock and vibration, along with its high-power demands, also made it less than the ideal display for use in portable scopes where size, weight, and ruggedness are of great importance.
Now, however, DSO color displays are taking on a new look. Last year saw the introduction of the first color DSOs with a flat-panel display. Two four-channel scopes in Gould Instrument Systems' DataSYS 700 Series, Models 720 and 740 (described later), incorporate a 6-in. color LCD and are priced at under $8,000. And continuing its downward pricing of color DSOs, Gould late in the year introduced the Model 500, a dual-channel scope (described later) incorporating a 6-in. color LCD and costing $4,000.
Right up to the end of the year, low-cost color DSOs remained in the spotlight. At that time, Hitachi-Densi introduced its dual-channel VC-5430 color DSO. This scope, with a 4-in. color LCD, costs only $3,000 and is smaller than a notebook computer.
Although color LCD DSO introductions were the most prominent last year, a new type of color CRT display was introduced last year by Tektronix. Called NuColor, this display is claimed to be not only less expensive than the traditional three electron gun, shadow mask CRT display, but to provide better performance. The display consists of monochrome CRT with only a single electron beam (see Fig. 2). A liquid-crystal shutter, incorporating ultra-thin optical switches with color polarizers and neutral polarizers, creates the color images.
This display, according to Tektronix, provides better color purity, convergence, and resolution than traditional shadow mask displays. Furthermore, with only one electron gun instead of three, the NuColor display provides higher reliability and lower power requirements. The display is proprietary, however, and only used in Tektronix DSOs–right now in the company's TDS 524A, TDS 544A, and TDS 644A described later.

CAPTIONS FOR INTRODUCTION:

Fig. 1. Multiple waveforms as well as their associated data are easily distinguishable on this color display.

Fig. 2. The latest color DSOs from Tektronix use a single-beam monochrome CRT with a liquid-crystal shutter instead of a traditional three-gun shadow mask CRT display.

Color DSO scopes: Here's what's available

A description of the performance capabilities and key specifications of color DSOs available follow. Only “traditional” instruments are included; PC-based instruments will be described in a future article.

$3,000 dual-color DSO is battery powered

The VC-5430 battery-powered color DSO comes with a 4-in. LCD. It measures only 7.2 x 10.2 x 2.4 in. and weighs just 4.4 lb. It fits into an attache case, making it particularly well suited to field service applications.
For its price and size, the dual-channel VC-5430 provides an array of excellent features. Among these are 50-MHz bandwidth, simultaneous 30-Msample/s sampling on both channels, 2 Kbytes per channel memory, a 100-waveform save memory, and a wide assortment of triggering capabilities including pre-and post-triggering, differential input and differential triggering, and frequency-divided triggering. Automatic pulse parameter measurements, cursor measurements, and go/no-go comparison are also standard VC-5430 features. An RS-232 interface is standard as well.
The VC-5430's built-in NiCd battery provides a typical operating time of 2 hours, and is automatically recharged. The scope can also operate from its ac adapter or from an optional external battery pack. ($3,200–stock.)
Hitachi Densi Ltd.
Torrance, CA
Rich Westle 310-338-6116
Fax 310-328-6252

200-MHz Color DSO costs under $4,000

The Model 500 dual-channel, 200-MHz digital storage oscilloscope provides full-color display capabilities for under $4,000. It uses a 6-in.-diagonal backlit color LCD screen to display signals, text, cursors, and graticules. Different colors can be used to distinguish multiple traces and alphanumerics, and a range of optimized color settings are provided using preset defaults.
The DSO provides a 200-MHz equivalent analog bandwidth, 200-Msample/s sampling rate for transient capture, and 2-Gsample/s repetitive sampling. It also has many post-storage waveform manipulation and processing features. These include the comparison of live real-time traces with previously acquired data, pulse-parameter calculation on live and stored traces, averaging, limits testing, analysis, and post-storage signal-filtering and mathematical operations.
Outputs are provided for external printers and plotters, and an optional internal color plotter is available. ($3,990; internal color plotter, $495–6 weeks ARO.)
Gould Instrument Systems, Inc.
Valley View, OH
Michael McCorkle 404-368-2170
Fax 404-368-2184

Mid-price color DSOs offers many options

Two color DSOs, DataSYS Models 720 and 740, offer a wide assortment of options along with excellent mid-range performance. The Model 720 is a four-channel (2 + 2), 150-MHz scope that has a 100-Msample/s single-shot (2.5 Gsamples/s repetitive) sampling rate, 50 Kword memory per channel, 360 Kbytes of nonvolatile RAM, and a 6-in. backlit color LCD.
Also included in the 720's basic price are waveform-processing capability (limits testing and averaging); automatic setup of vertical, horizontal, and triggering controls; status display of current instrument settings; and a wide variety of Y-T measurements (rise time and fall time, frequency, period, duty cycle, pulse width, and more). IEEE-488.2 and RS-423 interfaces, as well as four probes, are also standard.
DataSYS Model 740 provides four full channels, rather than simply 2 + 2 capability. Aside from its full four-channel capability, it provides the same performance and features as the Model 720.
A broad array of options helps tailor both scopes to specific applications. These options include X-Y measurement software ($300); mathematics and processing software ($750); software for setting up and storing test sequences ($450); Memory storage, consisting of a 120-Mbyte hard disk ($950); a 1.44-Mbyte floppy disk for transferring data to a computer ($600); a PCMCIA memory card ($450); and a four color plotter ($600) or a thermal plotter ($950).
Both scopes measure 15.1 (W) x 6.2 (H) x 19.0 (D) in. and weigh 34 lb. Power requirements are 90 to 132 or 190 to 265 Vac, 45 to 400 Hz, 250 VA. (Model 720, $7,500; Model 740, $7,790–4 to 8 weeks ARO.)
Gould Instrument Systems, Inc.
Valley View, OH
Stan Tofoil 216-328-7000

Four-channel DSOs provide fast sampling

These two color DSOs, Models 544A and 644A are identical except for sampling rates. Both scopes provide full four-channel input, 500-MHz analog bandwidth, 15-Kpoint/channel record length (50 Kpoints optional), embedded mass storage, segmented memory, FFT averaging, and template testing that includes math waveforms. And both incorporate the manufacturer's NuColor display described earlier. The only difference between the two scopes shows up in their sampling rates (and consequently, their prices). The 544A has a 1-Gsample/s sampling rate for one-channel operation, 500 Gsamples/s on two channels, and 250 Msamples/s on three channels. The 644A, on the other hand, provides 2-Gsample/s sampling on all channels.
Both TDS 544A and TDS 644A include a DOS-format, 1.44-Mbyte, 3.5-in. floppy-disk drive to facilitate mass storage and data transfer to a PC. Both scopes also include an IEEE-488.2 (GPIB) for programming and RS-232-C and Centronics ports for documentation.
Two other very useful features of these two scopes greatly extend their usefulness. A special acquisition mode called FastFrame allows the acquisition memory to be partitioned into as many as 910 segments with 50-Krecord length. And a special video triggering option enable the scopes to trigger on virtually any broadcast video signal format, including NTSC, PAL, SECAM, and HDTV.
Another color scope in the TDS family, the TDS 524A is essentially a two-channel version (two full plus two auxiliary channels) of the TDS 544A with half the sampling rate (one channel at 500 Msamples/s and two channels at 250 Msamples/s)–for close to $6,000 less. Except for the number of channels and sampling rates, most standard features and options are the same for the two scopes. (TDS 544A, $16,790; TDS 644A with two active probes, $19,895, TDS 524A, $10,900–4 weeks ARO.)
Tektronix, Inc., Beaverton, OR
Information 800-426-2200

Modular DSO offers wide range of performance

The 7200A is a modular DSO mainframe that accepts plug-in modules that go a long way toward allowing the user to tailor the scope to specific requirements. The color display, which is a 9-in. raster CRT, is built into the mainframe.
The 7200A accepts two plug-ins and can provide up to eight channels of simultaneous digitizing. Transient digitizing rates of up to 2 Gsamples/s or repetitive sampling rates of up to 100 Gsamples/s are available. These rates depend on the plug-ins selected. Up to eight traces of live, stored, or analyzed data can be clearly displayed by the 7200A.
Three different plug-ins are available for use in the 7200A: (1) the 7262, a two-channel, 4-GHz analog bandwidth, plug-in with 100 Gsamples/s repetitive and 40-Msample/s single-shot sampling, and 20-Kpoint memory; (2) the 7242B, a two-channel, 500-MHz analog bandwidth plug-in with 1-Gsample/s sampling on two channels and 2 Gsamples/s sampling on one channel and 200-Kpoint memory; and (3) the 7234, a four-channel, 500-MHz analog bandwidth, 200-Msample/s sampling, and 200-Kpoint memory. All three plug-ins provide triggering on pulse width, interval, pattern, or state/event qualified. The 7242B plug-in also includes TV trigger.
A wide range of analysis and mass-storage features are available with the 7200A. Analysis features include: FFT with up to 50,000 points; waveform parameters with statistics (histograms and trends); pass/fail testing; extraction of waveform features such as peaks, valleys, and transitions. Built-in mass-storage facilities provide both hard disk and floppy-disk drives. ($25,000 to $45,000 depending on plug-ins and options–4 to 6 weeks.)
LeCroy Corp.
Chestnut Ridge, NY
Art Pini 914-578-6020

Fast sampling and high bandwidth suit DSOs to any application

The HP 54700 series of four-channel, 8-bit DSOs consists of three basic models, the HP 54710D, HP 54720A, and HP 54720D. These are truly high-end DSOs, providing the performance features needed to handle most of today's high-end test applications. For example, the HP 54710D features 4-Gsample/s sampling on one channel, 2 Gsamples/s on two channels, and 2 Gsamples/s on up to four channels. The HP 54720D can sample at an exceptionally fast 8 Gsamples/s on one channel, 4 Gsamples/s on two channels, 2 Gsamples/s on four channels, and 2 Gsamples/s on up to eight channels. System bandwidth is 2.0-GHz equivalent time or real time.
Memory capacity of the HP 54720 is four channels at 64 Kpoints per channel, or two channels at 128 Kpoints each. For the HP 54710 DSOs, it's two channel at 64 Kpoints per channel or one channel with 128 Kpoints.
Besides impressive specifications, these scopes provide a broad array of very useful features. Typical of these features are 19 automatic measurements with user-definable parameters, mask testing with user definable masks, histograms, waveform math function including integration and differentiation and FFTs, built-in software calibration, 3.5-in. DOS-compatible disk drive, flash-ROM operating system, IEEE-488.2 (HP-IB) interface, and color output to HP printers. (HP 54710D, $36,400; HP 54720A, $50,900; HP 5420D, $53,900–10 to 12 weeks ARO.)
Hewlett-Packard Co.
Palo Alto, CA
Information 800-452-4844

DSO provides wide choice of triggering

The HP 54110D dual-channel color DSO provides the user with midrange performance for a price of under $25,000. Its 9-in. raster display allows the user to work with as many as seven colors at one time, selecting these seven from a total of 4,096 available.
Key scope features include 1-GHz repetitive bandwidth, 40 Msamples/s sampling rate, 7 bits vertical resolution (10 bits with averaging), and 1 Kpoint per channel memory. Flexible triggering facilities include pattern (4 bits wide), time-qualified, state, delayed, and holdoff.
The HP 54110D also provides a wide assortment of automatic measurements. These include frequency, period, pulse width, transition time, peak-to-peak amplitude, top and base voltage levels, preshoot, and overshoot. Waveform math functions include A + B, A – B, Invert A, and A versus B, as well as channel-to-channel time-interval measurements. ($24,900–4 to 6 weeks ARO.)
Hewlett-Packard Co.
Palo Alto, CA
Information 800-452-4844

RUNNING HEAD: Update on color DSOs