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A Review of HP's 1664A Logic Analyzer

On a trip last year I used one of HP's 16xx series of logic analyzers at a customer's site. The experience was simply awful. No one really knew how to use it. It's quite a powerful device, and comes complete with (it seems) zillions of on screen menus and selections. I was completely baffled, and was frustrated by the 10-15 minutes needed by the "expert" to change the simplest setup.

Some time later the engineers here decided to buy yet another analyzer to complement our test equipment suite. They looked at a lot of units, and quickly settled on the HP 1664A, the very model that caused so much trouble on my trip.

"OK", I warned, "you want it, you'll have to live with it no matter how awful it is". The unit arrived a few days later. Within a week it was in demand everywhere. Within two weeks they wanted to buy another.

Now that I've spent quite a bit of time working with this instrument I have to admit that it's really quite nice. It will trigger on anything you can dream of. Various options let you put in as many channels as you'll need. A scope option even turns the unit into a very fast digitizing oscilloscope.

It's not intuitively easy to use, though. Though the manual is huge it's just about useless. Even the most basic of terms, like "state mode" versus "timing mode" (which changes the entire acquisition scheme of the instrument) are not defined... anywhere.

If you have a teacher, you'll master the system in no time at all. Without one figure on some frustration and fiddling. The triggering menus, in particular, are quite confusing at first. With experience, operation is very fast; you can change a setup in seconds. The engineers at the place I visited must have been complete novices with this device.

Our unit came with 32 channels. Use 16, and it will acquire at a 2 nsec rate. With all 32 channels in play the acquisition rate drops to 4 nsec, which is still plenty fast for most applications. The unit's 4096-deep buffer is more than enough for most any need; if you require more depth it makes sense to tune your collection strategy to reduce the amount of data you'll have to scroll through.

Like any decent logic analyzer, setting the unit up to collect a lot of signals is tedious. This is more a problem with the complexity of the task at hand than with the analyzer. For each signal you must specify which probe to use, optionally assigning a name to the probe which is displayed with the collected data. Then, add this to the waveform display page. Set up your trigger modes, and you are ready to start collecting data.

Some folks skip naming their probes. Bad move. With more than a few channels displayed you quickly get confused about which trace corresponds to which signal. I work with the mouse in my right hand constantly updating the analyzer's setup as I move probes around and run other tests with my left.

Its full-screen display, on screen menus, and mouse make using this more like running a PC than a piece of test equipment. A built-in disk drive lets you save setups and collected data; it's also a boot disk that starts the machine up. I particularly like the double line the unit shows for logic zeroes. It helps you tell where ones and zeroes are on the display. Also nice is the built-in printer interface.

Scrolling through large data collections can be a bit slow. The "scroll" knob - a large rotary wheel - really needs a high speed motor! In fairness, you can use the mouse to instantly center the display on the trigger or on one of two movable markers. The markers scroll a lot faster than the data.

Like all of HP's equipment, this unit is built to run forever. We've had no quirks or problems.

At about $5k with 32 channels this unit offers an attractive performance/price compromise. Overall, we're quite happy with it. In fact, we recently bought a second unit, and the engineers are clamoring for more...