Scopes' array of features, performance, size, and price breaks new ground
By Dan Strassberg, Contributing Technical Editor -- EDN, January 5, 2006
To change the landscape in the market, a new digital-oscilloscope family needn't offer the industry's widest bandwidth or highest sampling rate, especially when the new instruments break ground in other ways. Tektronix's DPO 7000 series has 500-MHz, 1-GHz, and 2.5-GHz bandwidths, and two of the units capture 40G samples/sec on one channel. Only much more expensive, greater-than 10-GHz-bandwidth scopes equal that rate—albeit on two channels simultaneously.
Equally revolutionary, especially in a series whose prices start at $14,000, is the 2.5-GHz unit's optional 400M-sample memory depth. Moreover, when you use the scope in the single-channel mode, you can assign all of the memory to the one active channel, but you needn't assign the unused ADCs to that channel. Hence, at 10G samples/sec—four times the scope's -3-dB bandwidth—you can capture an unprecedented 40-msec record (equivalent to two full cycles of the European 50-Hz ac-line frequency). The 4× oversampling is more than adequate for preventing aliasing and is usually acceptable for reconstructing signals at the full 2.5-GHz bandwidth. Interleaving two or all four ADCs reduces the record duration to 20 or 10 msec but can improve the rendition of waveform details—in practice, though not in theory—by increasing the oversampling to 8× with two ADCs interleaved or 16× with four.
In addition, Tek delivers this performance in a package whose approximately 12-in. depth saves precious benchtop space compared with more conventional scopes and sports the industry's largest 12.1-in.-diagonal, touch-sensitive, color LCD screen, which has 1024×768-pixel resolution.
Another major development in the new series is the fourth generation of FastAcq mode, Tek's proprietary DPX digital-phosphor technology. Unlike earlier implementations, which offered only 1.25G samples/sec, the new version works at sampling rates as high as 40G samples/sec, a 32-times rate increase. The mode radically reduces the scope's "blind time," during which it cannot trigger, and quickly reveals transitory aberrant phenomena by bypassing the conventional time-ordered waveform memory and immediately placing acquired samples in a 3-D color-graded pixel map. The mode is limited to short waveform records, however: 1000 points in the new implementation, increased from 500 points previously. In all three members of the DPO 7000 series, the FastAcq mode captures as many as 250,000 waveforms/sec—more than all but the fastest previous implementation.
The new series also marks the introduction of the TekVPI (Versatile Probing Interface) probing system, which enables intelligent bidirectional communication between the scope and the probe and also accommodates older probes of conventional design. In addition to several active voltage probes, the new probe family includes a $2590, 120-MHz-bandwidth current probe that measures 1 mA to 30A (50A peak) without an external amplifier or power supply.
All units have four channels; standard memory is 10M samples/channel in four-channel mode and 40M samples/channel in one-channel mode. Prices for the 500-MHz-bandwidth DPO7054, 1-GHz DPO7104, and 2.5-GHz DPO7254 are $14,000, $17,900, and $24,900, respectively. Maximum sampling rates for the DPO7054 on four channels simultaneously is 2.5G samples/sec on each channel and 10G samples/sec on one channel. The comparable figures for the DPO7104 are 5G and 20G samples/sec, respectively; comparative figures for the DPO7254 are 10G and 40G samples/sec, respectively. Option 2SR doubles the DPO7054's sampling rate for $2000 and the DPO7104's sampling rate for $3500. Deep memory for the DPO7054 and 7104 captures 50M samples/channel on four channels and 200M samples/channel on one channel, and the price is $7500. Comparable figures for the DPO7254 are 100M and 400M samples/channel, respectively; price is $15,000.
All units come with several application-specific analysis-software packages on their hard drives. You can use each package five times at no charge. If you wish to continue using the package, you must purchase and enter an unlock code. All units come with Tek's MyScope software, which allows you to create custom user interfaces. The scopes' prices include continued use of MyScope, which requires no unlock code.
Tektronix Inc, www.tektronix.com.
