Newbie on the Steinmetz Equation

Use a thicker pencil ;-)

...Jim Thompson

Was that from the constipated mathematician joke??

D from BC myrealaddress(at)comic(dot)com British Columbia Canada

No. From observation: If the graph doesn't match the math, draw the graph with a thicker (leaded) pencil ;-)

...Jim Thompson

We had an ee lab instructor, a rather brilliant field theory PhD, who didn't like being a lab instructor. So he left early... very early. So we left, too.

At the end of the semister, me and my lab partner stayed up late and faked all the lab reports. I got good at sloppy slide rule slinging, which made very nice data point scatters, just as if we had done fairly careful measurements. We got A's of course.

It was just as well that we faked the data, as most of the lab equipment was broken.

John

Bwahahahaha! Twice in one week, we've pulled the same games in the past. Except, at MIT, we called it "fudging" the data. I got A's as well ;-)

...Jim Thompson

One experiment was to build an ac-coupled triode amp and plot its frequency response, using a signal generator and an ac voltmeter. But the lab-wide B+ power supply, to all the benches, had about 50 volts p-p of ripple on it, and I was the only one who knew.

John

I didn't believe that nonsense about pulling the field would cause a DC motor to speed up. I tried it. It did. It didn't blow, but did jam a rotor/stator pretty badly ;-)

...Jim Thompson

You forgot to post a link to the datasheet.

It's messy due to the website using an ActiveX control. (I think that's it.) I don't know how to provide a direct link.

Indirectly:

Steinmetz eqn is at the top of the page. Core loss vs Flux Density graph at row 1 column 2.

If needed, I can put the data sheet on my ISP webserver.

D from BC myrealaddress(at)comic(dot)com British Columbia Canada

Reminds me of when I passed the electronic instrumentation lab course at Drexel (though handing in most lab reports 1 week late)...

The last experiment was to build a simple analog computer to simulate "simple harmonic motion with damping", such as a pendulum swinging through an arc range small enough to have cosine of angle from vertical not straying much from unity.

The circuit was 2 op-amp integrators and some more op-amps arranged in a circuit resembling a "state variable filter", so as to have behavior described by the same differential equation that a damped sinusoidal oscillation has.

I was 1 of 2 students out of about 80 that "quarter" who got the darn thing to work. Usually, the oscillation instead of being damped, grew exponentially until limited by clipping at the point that the O-scope was usually connected to.

I saw a reason - the waveform at that point, before it grew to clipping at that point, looked to me not like a sinewave but a twice-integrated-squarewave. As in concave-towards-x-axis parabolic arches. That looks fairly similar to a sinewave, but generate that one at audio frequencies between 50 Hz and a few KHZ - the ears say that parabolic arches are not a sinewave.

But the frequency was low enough to watch the spot on the O-scope move up-and-down, maybe 2-3 Hz or something like that, but I had the eyes and mind to see how that was parabolic arches rather than sinusoidal.

Knowing that, I knew the signal got clipped somewhere before being integrated twice.

And knowing that, I looked at where the clipping was, confirmed its existence, and afterwards redid the experiment with smaller signal initial conditions to avoid the clipping that I saw. The result from that is that I got the lab exercise "experiment" to actually work properly - along with 1 other student out of about 80.

The only ones getting grades of A for that course were limited to:

• my fellow getting the last experiment to work,

• those completely avoiding imperfections in the lab exercises before the last one and the lab reports to write from the lab exercises,

• those doing well enough (probably over 93-95% of perfection) before the "last experiment" and doing the "last experiment" and the lab report therefrom well enough to get a D or a C or an "F good for 50%" rather than a zero for that one.

- Don Klipstein ( snipped-for-privacy@misty.com)

And it's called "massaging" the data when measured results don't quite fit with what you had in mind. A staple of big company politics and reporting :->

Dave.

that site just uses frames.

here's the URL of the pdf.

"Jim Thompson" schreef in bericht news: snipped-for-privacy@4ax.com...

It was a popular game in the chemistry laboratories in Melbounre. As a demonstrator I once had to castigate and mark down a pair of nuns who had submitted identical sets of results and calculations.

As a student, I only had to fake my results once, when the experiment proved to be impractical - when it didn't work, I went off to the library, found the relevant papers, which specified what you had to do the electrodes to allow them to settle to a stable voltage in a reasonable time, and explained why our experiment hadn't worked.

To show willing, I copied a column of the published experimental results into my report - making it clear where I'd got them - and used them to plot the graph we would have produced if the experiment could have worked, and worked out the result.

I got a good mark for the report, and I'm told that versions of it kept on reappearing - with other students names on it and without the references to the original literature - for some years.

Oddly enough, my father had run into a similar problem in the practical part of his final year examination, and had taken the same course, with the same result. He did have the advantage that he'd done most of his course half-time while working as a bench chemist, so his practical skills were notoriously good.

None of you could beat my favorite lab supervisor, twin blond girls, both working on masters, and they would switch off to give each other whole days off , only one was supposed to be the TA. We finally leaned how to tell them apart, one was smart, the other dumb. Just my luck, dumb wrote the final grades, I had to find smart to get it fixed.They had mastered the art of being "forgetful" when you asked them about past events.

Eagle Scout's word of Honor, I did have good looking twin blond female lab supervisor(s)

Steve

Thanks for the correction and the link. How did you figure out the link? According to:

D from BC myrealaddress(at)comic(dot)com British Columbia Canada

Yes, and NASA has been a leader, "massaging" GW data.

right-click -> this-frame -> view-source

Then I examined the form associated with the dropdown, and noticed what looked like URLs in the form so I tried one of them

If it hadn't worked I'd have had to examine the form in more detail and figure out what clicking 'go' would do.

In this case it simply runs some javascript that goes to that URL.

yeah links to frames can be tricky in that it can be impossible bookmark some configurations of the frames.