Review: Agilent U8002A PSU

There’s a lot of debate out there over the merits of asking someone what they want for Christmas.  Does it defeat the purpose of buying thoughtful gifts which show how well you know someone?  Or does it accomplish the real goal of giving presents which are truly useful and desirable?  Well, I personally don’t have a problem with being asked what I’d like for a present.  Particularly when I can request, and receive, a sweet power supply like the Agilent U8002A:

Agilent U8002A PSU Yes, Santa my parents were very kind to me this Christmas.  Finally, more than 15 months after considering a handful of different supplies, I have one to call my own.  And interestingly, it wasn’t one of the supplies I discussed in my original list.  But I think it still meets my original set of requirements fairly well:

  • Output voltage: 0-30V, 10mV resolution
  • Output current: 0-5A, 10mA resolution
  • Output voltage ripple: 0.01% + 2mV (5mV @ 30V)
  • Output current ripple: 0.02% + 2mA (3mA @ 5A)
  • Cost: $396

So far I’m very pleased with this supply.  My multimeter indicates that its voltage and current readings are spot-on.  This is no surprise though, considering that it came with a calibration certificate from Agilent.  I also attempted to measure its output voltage ripple using my Red2 IOBoard, but quickly discovered that I didn’t have the necessary ADC resolution (in other words, the output was so clean I couldn’t measure any ripple or noise).

The interface on the U8002A is quite nice.  Simple yet powerful.  I particularly like the fact that I can adjust its voltage and current limits before enabling the output.  This is one feature that would have been missing in most of the cheaper power supplies I looked at.

Agilent U8002A - Display Limits while Off

Just out of curiosity, I ran one more test while I had my IOBoard out and connected. I connected up a 20Ω resistive load and enabled the output while logging data:

Agilent U8002A Power-on Response

That little cut in the voltage just before the output reaches steady-state is a little odd.  Not that I’ve looked at a lot of PSU transient responses though.  It just seems like the control is doing something strange there.  Perhaps some sort of filter capacitor gets switched in and we hit a brief current limit?  Who knows…  It’s not a problem though.  I’d be more concerned if the voltage had overshot the limit, but that’s clearly not the case.

Overall, if you’re looking for a PSU with specs like this one, I’d highly recommend the U8002A.  It’s made by Agilent, so you know it’ll be a quality piece.  And yet it’s reasonably priced (unlike most of their hardware).  Let me know if you have any questions about it.

Ozone and Earthquakes?

Tangshan Earthquake (1976)The words “earthquake” and “ozone” are two terms you don’t often find used in the same sentence.  Like “congress” and “effective”, or “health food” and “delicious.”  And yet, MSNBC recently published an interesting news item whose title did just that: “Is ozone gas an earthquake precursor?

As it turns out, when rocks such as basalt and granite are crushed, they produce substantial quantities of O3 – ozone gas.  According to researchers at the University of Virginia, the amount of ozone released varied between 100ppb and 10ppm.  To put that into perspective, the low end of this range is comparable to a very smoggy day in Los Angeles.  The high end is one hundred times worse.

So I guess now we’ve got yet another reason to hate earthquakes: they split houses, swallow cars, and pollute the air.  Although, perhaps if a quake destroyed enough cars this would offset the amount of ozone released.  But I digress.  The real question here is, “Can elevated ozone concentrations predict earthquakes?”  Well according to researcher Catherine Dukes, no, not really: “It’s just a way to warn that the Earth is moving and something — an earthquake, or a landslide or something else — might follow.”

I suspect that any rock crushing action which produces ozone is also detectable via seismograph (although I’m just guessing).  So perhaps this discovery isn’t so useful.

But crushed rocks producing ozone?  This is still a rather strange phenomenon.  Scientists are not yet certain of the precise mechanism at work here, but suspect that differences in electric charge between rock surfaces are the most likely cause.  As you may know, lightning strikes are another natural means of ozone formation, particularly in the upper atmosphere, where ozone is more beneficial.  While the strike itself does not directly form ozone, it breaks apart O2 into atomic oxygen, which may then recombine as O3 (see this PDF for details).  Lightning also yields nitrogen oxides (also a popular automotive pollutant) which, in the presence of sunlight, react with other chemicals to form ozone.  So the theory here is that differences in electric charge between the crushed rocks are producing small electrostatic arcs (miniature lightning strikes) which result in ozone gas.

Well, perhaps we should just chalk this up as another oddity of the universe – like X-ray-producing tape, or radioactive bananas…  Still, it would interesting to know if there are preliminary tremors which aren’t detectable by seismographs but might be picked up by ozone detectors.  Such predictions probably wouldn’t be too accurate though.