really nice Rigol scope

I've been coveting one of those for a while. Iwatsu make some interesting similar stuff, too.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Lousy design. I'd do a lead-acid charger to current limit at maximum rated charging current, coming out of current limit when current falls, to regulate at 13-point-whatever-the-battery-manufacturer-recommends-for-charging. Hell, I can do that with a 723 with a bit of boost :-) Add a timer, or minimum current sense and switch off, you've got it nailed.

AKA "Using local materials".

You sure you've never been in the Military?

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

I've never managed to get my hands on one of those. How good are they for looking at close-in noise?

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

I don't think they want it to do that. I think they want to sell more batteries. Where's a good class-action lawyer when you need one?

Well, I was in the Navy for a week, but that's another story.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

Not a lousy design at all, just that a lawyer was present at the product specification meeting.

Thanks for pointing that out.. I think I ran into these once, but couldn't justify more than a few $100s. I'll stick this in my amplifiers bookmark folder...

--
_____________________
Mr.CRC
crobcBOGUS@REMOVETHISsbcglobal.net
SuSE 10.3 Linux 2.6.22.17

I used an ancient Tek analyzer that allowed you to add delay as needed in addition to the automatics delay based on the BW.

Well John, are you interested? I didn't contact them yet, but I am happy to.

--
_____________________
Mr.CRC
crobcBOGUS@REMOVETHISsbcglobal.net
SuSE 10.3 Linux 2.6.22.17

One of my guys did talk to some folks at Agilent. Thet said, no, it doesn't do that, and it won't.

There is an Agilent Youtube video that shows how to make the measurement. All you need is a PC and Matlab.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

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I notice you are using the NXP Cortex M3, LPC1768. We are looking at that too, though it seems STs STM32L151 is going to win that fight

Any specific reason you opted for that Cortex device?

Thanks

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We had been using 68332s and figured it was time to move on, so my guys did some research. We wanted a range of parts from one vendor, and one part had to have a memory bus, and one had to be small and cheap. We care more about compute power than power consumption, and cost is not a big deal. Some of the available parts just didn't have enough port pins. Coldfire looked good, but Freescale was on the edge of bankrupcy. My guys settled on NXP, LPC3250 for higher-end use and the 176x parts for small stuff. We use the Code Red development stuff, based on the GCC compiler.

It all works pretty well, except that the NXP documentation is mediocre, so we have to experiment sometimes to get stuff to work. I suppose that's normal these days. The CPUs are fine, the PLLs are confusing, and some of the peripherials are probably outsourced IP so not documented very well. But it all works, and the chips are reliable and very fast. The 1768 runs at 100 MHz, but we often throttle it down. The LPC3250 is a beast, 270 MHz, DRAM controller, cache, vector floating point.

We run one fairly complex filtering and PID algorithm on the 1768 at

100 KHz. We clock that at 50 MHz, half the available speed. This board has 13 CPUs, one master controller and one per isolated channel:

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

They are not being very nice then, are they? Then again, persistence sometimes pays off. I will see if I can find out if they are willing to not be stupid.

I doubt there is a good reason they can't make the instrument do this. There should be no need for the user to have to use Matlab--which is not a trivial added expense.

--
_____________________
Mr.CRC
crobcBOGUS@REMOVETHISsbcglobal.net
SuSE 10.3 Linux 2.6.22.17

A good connector should be able to handle 2A. Still, my application usually draws much less than 2A but more than 1A.

--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------

Can you find out who you talked to at Agilent, and let me know, here or at snipped-for-privacy@sandia.gov

Agilent is interested and "wants to know."

--
_____________________
Mr.CRC
crobcBOGUS@REMOVETHISsbcglobal.net
SuSE 10.3 Linux 2.6.22.17

Rob, who bought the counter and contacted Agilent, is on vacation for another week or so. Agilent is welcome to call me and I'll explain the situation.

But the requirement is simple: measure a time interval or a period, and, every N samples, display the mean and standard deviation. A

40-year-old 5370B does it just fine, and came standard with an OCXO too.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

Ok, well knowing the old model helps, and I will see if they have any inclination to call you.

At this point I sent a note to a guy who manages the team that built the

3000X series scopes, and he cc-ed the guy who used to be my main point of contact for the 7000 series scopes (some sort of manager, but more marketing oriented) and a lady who is related to the team behind the 3352xA series arb. generators recently released in tandem with the new counters.

So now there are 3 folks over at Agilent who are aware of this.

The new generators run Windows 7, as does the 3000X and 2000X scopes (thank God it is invisible to the user). The counters do too, I think. So the software to do what you want is practically already written, because they did it for me in the 3000X scope. I bet they could almost transplant it, with a few UI mods to the counter. Well, it might not be that simple, but at least I am 100% certain there is no reason the counter can not do what you want.

They would have to be pretty idiotic at this point to give up on a good PR opportunity by not putting this feature in your counter. I will keep working on it from my end. Last time it took a few weeks of pestering and explaining precisely what I meant. Eventually they let me talk directly with a 3000X engineer. He got it quickly.

Then the firmware came out a month or two later with my desired features.

--
_____________________
Mr.CRC
crobcBOGUS@REMOVETHISsbcglobal.net
SuSE 10.3 Linux 2.6.22.17

It's interesting that, as I understand it, your Agilent scope didn't do the same basic calculation that the 53230A counter doesn't do, namely measure and display jitter. A Tek 11801 scope from the 1990s does that. It's a simple, fundamental measurement for all sorts of applications.

On a 5370B, you punch one button to select TI or Period, one button for sample size, then press "MEAN" or "STD DEV" to display the thing you want.

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation

Well, what it did was compute statistics on measurements, with an accumulating number of samples only. There was a "reset statistics" button which would restart the accumulation.

So if I wanted to see how something changes, I'd have to press that stupid button.

Critically important is the ability to select sample size. Obviously, a finite sample size implies a moving average, with the stats calculated from the past N samples.

This doesn't require resetting an accumulation, and is a more sensible implementation for an instrument with the intended purpose of real-time dynamic visualization of signals.

So Agilent added a soft-key&knob UI enhancement to set the sample size. It may be set to infinity, in which case it simply accumulates like before. But when set to a finite value N, it computes the stats on the past N measurements moving average style. Great!

The other nice touch they added was optionally normalizing the standard deviation to the mean. Ie, relative standard deviation. With laser pulses for ex., you may have less jitter as the pulse energy increases since the laser is operating much higher above threshold. So we expect to see less relative std. dev. at higher pulse energies, even though the absolute std. dev. might still increase a bit with increasing pulse energy.

Thus, we want to measure (and see in a spec. sheet) the pulse to pulse energy stability, which is understood to be normalized to whatever pulse energy.

So the Agilent 3000X now allows pressing another soft key called "rel. std. dev." that makes the std. dev. value in the stats table be actually: (std. dev.) / mean

I don't know what would happen with a zero mean, but obviously this function isn't meaningful except for cases expecting a non-zero mean.

So with rel. standard deviation and moving average stats, I can simply set up the scope to measure laser pulses or whatever, and twiddle optics while looking at the mean (absolute pulse energy) and the relative std. dev. (pulse stability, normalized) and make the laser work best.

The only problem now is the 3000X is still completely outclassed by my (2x as expensive) LeCroy's data analysis capability, so that the LeCroy is still what I would drag to a lab to do a laser job. But for simpler situations, like the discovery the other day that under certain extreme cases my LED pulser could actually produce non-trivial amounts of jitter, I used the 3000X relative standard deviation feature since I didn't need a fancy trend plot.

Hmm, maybe I don't really need the LeCroy anymore after all. It's just really cool!

But I am very appreciative that Agilent listened to my requests and implemented them. It is true that I was very persistent, worked my way up the food chain, and was very polite and professional--making certain at every turn that I was hoping they would like my ideas so that they could not only please me, but could sell more scopes and "grind Tek into dust" as well as making me more inclined to buy more copies of the scope in the future, etc.

Finally, there is no reason they should not or could not add these capabilities to the new counters.

Nice instrument. Some oldies were goodies.

--
_____________________
Mr.CRC
crobcBOGUS@REMOVETHISsbcglobal.net
SuSE 10.3 Linux 2.6.22.17