Brad,
This may be diy land but as you pointed out careful handling and knowledge are something you do need when you start working with potentially dangerous chemistry. I will always remember the skin peeling off the end of my finger from simply putting my finger over the end of a pipette and lifting some sulfuric acid, a lesson well learned. Safety gear and knowledge are a real requirement once we go beyond simply using a soldering iron, and do grab the right end!
This may be diy land but as you pointed out careful handling and knowledge are something you do need when you start working with potentially dangerous chemistry. I will always remember the skin peeling off the end of my finger from simply putting my finger over the end of a pipette and lifting some sulfuric acid, a lesson well learned. Safety gear and knowledge are a real requirement once we go beyond simply using a soldering iron, and do grab the right end!
Except you want to diode connect the transistor to measure Vbe at some collector current and ambient temperature. Extrapolating back to the bandgap voltage at -273C gives a good guess for Vbe vs T at I.
The base current does not matter.
For high speed testing of power mosfets, the body drain-source diode is used to measure the die temperature during final test. The reason every auto qual'd die temp is measured after a high energy pulse is to test the die-header interface. If the attachment is not 100%, you can see it in the die temp (x-ray only no good - it only picks up voids and not problems with the die-header solder joint quality).
These devices go into ABS and EMU i.a.o. (safety critical applications).
Ed could use a similar approach, after calibrating his device, to measure the die temp using Vbe as you suggest.
I can't resist a story here. When I was taking a chem class in junior high summer school so to avoid a conflict with a music course, I was a bit ahead of the class, many of whom were repeating the course due to failing it during the regular sessions. The instructor was an amusing character and put me to work preparing things in the back room.
One job was to prepare a reagent for detecting ethanol. I was given a recipe that was not terribly clear, as it called for adding potassium permanganate to sulfuric acid. It turned out that the KMnO4 to be added was to have been a very dilute solution. But I thought they wanted actual crystals dissolved in the acid.
I had the H2SO4 in a test tube. The crystals I added weren't dissolving very fast, so I grabbed a wooden stirring stick. Things began to crackle, and I pulled the stirring stick out, to have part of it more-or-less vaporize with a bang.
I reported this to Morris Q. Mack, and he and I agreed that the outcome of the demonstration of adding ethanol to the mixture could have ended badly.
I was taken off of preparation detail at that point.
If believing in circuit theory makes me a dogmatist then I plead guilty. It's funny how true believers get upset when one of their criticisms is returned with a few words changed so that it better fits reality.kamis said:
Is there not a risk of reducing bandwidth by adding lumped inductance? Anyway, why would anyone need 75 ohm RCAs? If you need 75R, use BNC.jneutron said:
We had a really smart researcher open an enclosure to change the specimen being x-ray'ed.
yes, you guessed it... he didnt turn off the x-ray machine nor did it have a safety interlock on the door.
Result? One BBQ'ed hand which was amputated.
Practical experience is sometimes learned the hard way.
THx-RNMarsh
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Stare at each other, wait till we die
Stare at each other, wait till we die
Probably come to die in this town
Live here my whole life
There's kerosene around
Something to do
There's kerosene around
She's something to do
--Big Black
Yeah, I remember that case study being used in the (what felt like hundreds of) hours of safety instruction when I was at LLNL as an intern. Sad story to say the least.
The midwest in a nutshell, that one is in permanent rotation. I nearly did a double take when Anthony Bourdain interviewed Steve Albini (somewhat older and a little chubby) on Chicago cheap eats.
That's what I was sayin' too.
Drill a hole central in the heat sink and fit a thermocouple into the hole.
Place the preamp in a toaster oven and with another thermocouple monitor the 'ambient' temp, set point 50C.
Let it run for extended period (12 hours) until temps stabilise.
The final heatsink temp will give you a pretty close guide to transistor temp as stated in above post .
What is the rise on ambient of the heatsink with the preamp case fitted ?.
Dan.
Pretty little Black boy,
your life is filled with sorrow,
I know it's hard for you to smile
Would you like to walk with me,
from that dead end street ?
Would you like to take my hand,
and will follow to the promised land ?
(Sweet Cream '65)
Same thing with the folks that developed laser trimming, "What's wrong, let me look down the optical path".
Well your experience came through earnest effort on your part.
My little deed during one science class was to pour sulphuric acid into the tadpole tank when the no-one was looking. By the end of the two hour session the tadpoles were all belly-up in the tank.
Questions were asked, but no answers were forthcoming and I never did own up.
Sorry tadpoles - I was a sh1t
Sy will understand this one. I was manufacturing polyurethane plastics and had barrels of urethane polyol and drums of isocyanate that together form polyurethane. Well one of my guys was as one of my workers called him, a box of rocks, no brains. He would stick his hands in the isocyanate side of the chemistry and not wear gloves when working on the machine. Needless to say your skin would end up looking like a nasty brown color but this didn't seem to stop him. So we had to resort to telling him he was putting his hands in Cyanide, not really, but it got the point across. Needless to say after I fired the guy I got a visit from Cal-OSHA coming to bust me for open containers of cyanide. Once we said the words polyurethane and MDI-isocyanate resin he put his gear away and proceeded to write me up for not having the weight limit on my forklift clearly in the operators line of sight! He had to find something wrong to justify his trip. Sometimes it is just so hard to get through to someone that you aren't making them wear protective gear just to make the job harder but to protect them.
It's been mentioned before, but this is always a source of hilarity for me. Things I Won’t Work With Archive | In the Pipeline . Also makes me wonder why some research chemists do what they do.
If you haven't read the blog before start with Sand Won’t Save You This Time | In the Pipeline
If you haven't read the blog before start with Sand Won’t Save You This Time | In the Pipeline
In this vein, there's a great Invisibilia podcast (great series!) on oil rig safety:
Oil Rig Workers Get Vulnerable To Make The Job Safer : Shots - Health News : NPR
My mom, a geological engineer who worked on natural gas rigs in West Virginia before she had me, has plenty of stories about that world, too.
Oil Rig Workers Get Vulnerable To Make The Job Safer : Shots - Health News : NPR
My mom, a geological engineer who worked on natural gas rigs in West Virginia before she had me, has plenty of stories about that world, too.
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On my personal "why in the world did I agree to do this?" list, there's superacid (HF + SbF5), trialkylaluminums (instant explosion with even the slightest contact to air or moisture), and arsenic pentafluoride. NaK alloy can also be pretty nasty, especially when used to dry THF.
These days, I stick with siloxanes (bad joke) which are pretty innocuous.
These days, I stick with siloxanes (bad joke) which are pretty innocuous.
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