PIC example : using a diode as temperature sensor

Like this?....

,---/\\/---, 470k +5 --+--/\\/--, | ,--/\\/--, roughly, | | 2k | __ | Vo = Vd1 + G(Vd1-Vd2) ,--|

That's okay, but in the old days I just kept a single assembly of diode already soldered to long teflon insulated leads and used the diode check function on the Fluke VOM, which reports Vf to one part in 4000 or something, to read the temperature rise. I also upgraded this to measure water temperature when I was canning tons and tons of homemade cucumbers for pickles- yummmm- a 10 year supply of perfectly formed, flavorful and naturally produced pickles grown from five plants on a trellis not 10' long.

There ya go !-)

...Jim Thompson

,---/\\/---, 470k +5 --+--/\\/--, | ,--/\\/--, | | 2k | __ | ,--|

Put some current flow numbers on it and report back ;-)

...Jim Thompson

Haha- should have said homegrown...

Ok, now I have a question.

If only the diode is on the neg input is to be used, do the extra resistors on the pos side effect the output linearity?

Also, if this is running on only a plus supply, and the output must stay positive to interface to an a/d input, would it be more advantages to use the previous design with a built-in positive offest?

Luhan

Hey Luhan! Pay attention! Think! Stumbles stumbled again ;-)

...Jim Thompson

A simple answer would be helpful. If this design causes the output to rest at zero, as implied, it would be useless for certain uses. Yes, no?

Luhan

I almost never give direct answers. I try to cajole the student into thinking... apply Ohm and Kirchoff...

Stumbles' "solution" diverts almost all the current away from the diode.

...Jim Thompson

Hmmm, maybe why I did so poorly in school. My attention goes more toward practical applications rather than theoretical designs, and 99% of what I do lately is software.

I'll just hang out here and see what shakes out.

Thanks guys, Luhan

Bwahahahaha! What happened to your claim of picking off the "old guard"? You can't even do Ohm's Law

...Jim Thompson

When I get a class that starts thinking they are hot tuna, I slip this sucker into the midterm or final:

1. Which of the following is a correct statement of Ohm's Law:

A. E = I * R B. R = E / I C. I = E / R D. All of the above

Let the games begin!!

Jim

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

Actually, its more of the new crop of engineers that are somewhat clueless in real-life working situations. One engineer I hired once asked me to explain what a resistor actually did. He did fine with digital and processors.

I could show you some tricky code snippets and ask you what they do, but that is outside of your field and I would not really expect it of you. Sorry if I'm just not inclined to solve of bunch of simultaneous linear equations for the fun of it. I've been constructing new innerds for a hacked radio-control car to make it autonomous and annoy my cat. (circuit available on request)

Just so you know. E=I*R, P=I*E and I can do all the permutations and combinations of them too. Also, if dim memory serves, all of the currents going into and out of any node must sum to zero. Known as Kirkoff's "no free lunch" theory.

Luhan

I was on conference call to one of those yesterday. At my current stress level I almost swatted him like a fly... what an ignoramus.

I might surprise you. YEARS ago I used to write Basic... no GUI's, just cranking numbers. I've also done a lot of Pascal, but still no GUI's, I've always left that to the older son. But I'm thinking of giving PowerBasic a shot... Larkin thinks highly of it.

Not in this case, you solve one and substitute into the other... rather trivial.

...Jim Thompson

So you get into software about as far as I do into analog. Yea, its good to know a bit about everything in your field, but I think today you really have to have a niche to get work.

The next time I actually NEED to solve some equations for an analog design, I'm sure I'll be able to do it. You have convinced me that I'm just a bit lazy in this area. It's always so much more fun to work at what you are really good at.

Regards, Luhan