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help with voltage reducing, then amplification

hevans1944

Hop - AC8NS
Jun 21, 2012
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I myself will be commissioning into the Air Force in May, its going to be a challenge, but a great one!
My father served during WWII as a lieutenant and bombardier on B17s. He got shot down during the end of the war bombing Berlin and served the remainder of the war in a German prison camp before being liberated by George Patton's army. I was born while he was still a prisoner, and my brother was born two years later, after Dad returned to the States to be stationed at Lowry AFB in Denver CO. After the war he served as a bombardier/navigator on B-29, B-36, and B-47 bombers. We moved all over the country every year or two. He had only advanced to captain before acquiring tuberculosis of the kidneys while stationed on Okinawa. That removed him from flying status while he spent a year in Phoenixville PA recovering. He retired as a major at his last duty station in Smyrna TN in 1962, to go into business with his brother-in-law. He had only a high-school education, so his advancement in rank was limited by that. He wanted me to go to MIT after graduating from high school, but I didn't want any part of that. Dumb choice on my part.

After I graduated from high school here in Dayton OH I signed up for a four-year hitch as an enlisted man. Did my four years, got a nice job, and finished my degree. It is sooo much better to serve as a commissioned officer than as an enlisted man, so congratulations on that. And, yes, it will be a challenge, especially if you decide to have a family. Moving around all the time is the nature of armed service, any branch. The government puts you where they think you will do the most good for the country, which doesn't often match up well with what you might think is best for you. Still, even as an enlisted man, I enjoyed my four years serving as a "mechanic" maintaining an ASG-21/MD-7 dual Ku-band radar-controlled fire-control system on B-52H heavy bombers. The Air Force taught me about a wide range of electronics, state-of-the-art stuff back then. That 20mm Gatling gun packed a mean sting, but fortunately we didn't have to use it except for training missions. Some of my Air Force training school classmates went on to service older model B-52s with different fire-control systems, flying over Vietnam but based in Guam. Gunners were enlisted NCOs back then, a tradition carried forward from WWII bombers but abandoned today.

It's a whole different army today. I have a step-son who has served several tours with the infantry (his choice) in Iraq and Afghanistan but, like most veterans I know, doesn't much want to talk about it. The Air Force (and if close enough, the Navy) plays a big role in close-in ground support of infantry. You don't win wars from the air, not without using nukes which would be abominable but not unthinkable. It takes boots on the ground to go in whup ass, but we seem to have lost the upper-level guidance on when and where it is necessary to do that. Plenty of "how" though and it gets better every day. Jeez, they are even letting enlisted men and women (non-commissioned officers) fly drones now, although not armed ones yet. I might have stayed in if they had that in my day.

I hope you will have an interesting Air Force career. Try to swing a job in a laboratory if you can. My best friend served in the Air Force at the Foreign Technology Division at Wright-Patterson AFB here in Dayton. After that, he segued into a similar job as a civilian, serving eventually as my boss until he left to form his own business. The Air Force contacts and security clearances helped a lot in his "new" job. You get to meet all sorts of interesting (and influential) people.

Hop
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
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Hop, I love reading your stuff. As stuff goes you have a lot of it and it's always interesting! :)

Chris
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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From now on I'm going call you Harry Callahan! :p

Chris
Really? I liked the Dirty Harry movie series, but disagree with the comment about limitations. A man never knows his limitations until he actually runs hard up against them. At which point most of us will try to find a way to get around those limitations. Doesn't always work of course, so we suffer the consequences, but to accept limitations is unseemly for human beings. If we "knew" and accepted our limitations, technology would not exist and we could return to the Dark Ages.:eek:

Of course... you could always make your own 'reference' voltage and then do the same trick... take the difference between the reference and the + sensor and you can get similar results.
That does work... sort of. You lose the benefit of temperature compensation from the four closely-matched piezo-resistors, and since all four are active components of the bridge (no passive dummy bridge-completion resistors) you also lose half of the sensitivity. So, instead of 100 mV full-scale output from both sides of the bridge, you have 50 mV full-scale sensitivity from half of the bridge. Sorta defeats the whole purpose of using a Wheatstone bridge configuration when you use only half of the bridge.

Still, it does work and is commonly used (with passive bridge-completion resistors) for single or dual strain-gauge elements where temperature compensation is not important and adequate sensitivity is provided by one or two strain gauges.

Sorry for the late comment, @Gryd3. This thread is mostly complete unless @David Stamper has more to say. Thanks for your contribution, especially the idea of making actual voltage measurements! A sensitive DVM keeps it real.
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
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Really? I liked the Dirty Harry movie series, but disagree with the comment about limitations.

Damn! I'm glad I didn't say it! :p

Anything else? Feeling lucky? Go ahead! Make my day! :D
DirtyHarry.jpg


BTW, Briggs didn't!
Chris
 

hevans1944

Hop - AC8NS
Jun 21, 2012
4,878
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Poor Harry, always under-armed with that pistol when everyone knows a rifle does the job from afar. Sean Connery's character said in the Untouchables to never bring a knife to a gun fight. I say never bring on a fight without overwhelming fire power. Learned that from the results of HIroshima and Nagasaki. Luck has nothing to do with it. Preparation is everything.:D Like when you dragged that pipe down the street behind your bicycle. I might have attached a roller skate instead of stick to the bottom end, but whatever works, works.:)
 
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