Products > Test Equipment
Test Equipment Anonymous (TEA) group therapy thread
Cerebus:
--- Quote from: mnementh on July 05, 2022, 02:37:45 am ---Except that generating and delivering an equivalent amount of heat as electricity is an order of magnitude less efficient than burning the natural gas directly to heat your food or water. No matter what mumbo-jumbo they're spouting, you still need to expend a certain amount of kilocalories to heat a galllon of water or to cook a dozen eggs.
--- End quote ---
Except that the pots and pans we use are horribly inefficient. You only have to hold your hand above the edge of pan on a gas cooker to realise that an awful lot of very hot air is rushing past the pan and not having its heat extracted from it. A while back I saw some pans that, unsurprisingly, had a bottom and sides that looked very heatsink like which improved the efficiency of the pan by at least a factor of two.
On the other hand it's hard to believe that the inefficiencies and losses involved in electricity are not going to be bested by a well designed water heater. Both burn gas in the first place, the thermal efficiency of heat transfer to water is probably going to be similar in both cases, but electricity then has generation and transmission losses to cope with. Obviously there are some indirect transmission inefficiencies in distributing gas too, pumping the stuff uses significant energy (There are 520 MW worth of gas turbines just used to pressurise the UK national gas core pipelines, before you consider what's used for local distribution). For heating hot water both methods could of course be greatly improved by using the energy not to heat the water directly, but to drive a heat pump to heat the water - even if you only get a CoP of 2 that's a huge efficiency gain..
Specmaster:
--- Quote from: Cerebus on July 05, 2022, 01:05:56 am ---
--- Quote from: Specmaster on July 05, 2022, 12:49:03 am ---Yes indeed it is an iPad Air 1, model is A1474 as printed on the back cover, but according to the model number in the settings menu it is MD768B/B for which I can find zero information.
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I don't know why Apple chose to describe that as "Model Number" in the UI when it's what they describe everywhere else as an "Order Number" i.e. the number you have to quote to get a model number A1447 with the right options, country specific stuff and so on. If you tap the actual displayed order code in that field it changes to the actual model number. Go figure...
--- End quote ---
How odd, I just tried that myself. I'm guessing that it must be some code that Apple use for something but what?, surely anything that is country specific would be flagged in the about tab anyway and all references on internet all mention MD785LL/A :-//
ch_scr:
--- Quote from: Vince on July 04, 2022, 11:52:47 pm ---
--- Quote from: mnementh on July 04, 2022, 11:34:36 pm ---
--- Quote from: Vince on July 04, 2022, 10:08:31 pm ---Fuck cars and smartphones, all junk.
Instead let's do something on topic and much more interesting : have these 3 lovely cans with lots of gold plated leads, how sexy.
Can't identify them. Does any old beard here have a clue what they are ?
First two from the left, the two shortest ones, have 8 leads. The third / taller one has 10 leads no less.
Probably some vintage OP-amp or comparator or linear voltage regulator I assume, but well... Google didn't help me here.
EDIT : if you know the answer but DO NOT have an old beard, that's fine, I will listen none the less.
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Your Harris Op-Amps are attached below. That Texas Instruments CT305 is being a total cunt. Even TI doesn't want to admit to it. :-//
mnem
Maybe we need to call it a CunT305...?
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Thanks BD and Dragon, I knew TEA was worth something ! :-DD
I have already downloaded the two datasheet and had a look, then refreshed the TEA page and saw Dragon attached them, how kind ;D
So wow... can't believe it, this 2525 is a RACE CAR !!!! 120V/µs 20MHz ?!! :wtf:
The 2215 is his little brother, 12MHz 60V/µs, still not shabby eh !
Wow, 120V.... so far all the op-amps I garnered were at best 20V for the TL054.. and have some that do LESS than one volt IIRC ! :scared:
So 120V for a vintage part.. just wow....... wow.
You can bet your ass I will keep these two little guys preciously ! :-DD
Can't help, I now feel the urge to wire them up and see that slew rate for myself ! Datasheet specifies what parameters to use to have a chance of getting that...
Too bad for the TI CT305 ... if anyone knows.... it says " 814 " at the bottom... maybe it's a date code, 1981 something ? So if I can find a 1981 scanned TI catalogue, or close to 1981, I might find the datasheet for that IC....
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Vince beware! These are uncompensated amplifiers. Which means they are fast, damn fast! But this also means they will oscillate below a certain amplification, usually 5 or so. Have a close look at the datasheet. Which means you can't just set them up as a buffer to try them out and you also have to take care to decouple them appropriately (100nF ceramic cap close to the IC for both rails to gnd, as a starting point). Fast Opamps can be temperamental, have a look at Jim Williams Application Note #13 for a short intro and at #47 for a deep dive. These app notes (and all of Jim Williams stuff really...) are a treasure trove of information, have fun!
bd139:
They have an external compensation pin so you shove a cap between that and ground to bring them back to docile normality for testing. 220pF or so would slow it right down.
Aaaand now I’m going to be stuck reading AN’s for the next day :-DD
vk6zgo:
--- Quote from: mnementh on July 05, 2022, 02:37:45 am ---
--- Quote from: Zucca on July 05, 2022, 12:27:29 am ---
--- Quote from: tggzzz on July 02, 2022, 09:22:44 am ---In the UK gas is much cheaper than electricity, and is commonly used for central heating, water heating, and cooking.
--- End quote ---
I have two problems with gas.
1)
Look at the efficiency of my gas water heater:
I can't sleep at night when I thing that 38% of my DHW gas (bill) is going to heat up the sky/stars.
2)
BTW: I adore climate town YT channel.
That's why I am switching to a Rheem Pro Terra
--- End quote ---
Except that generating and delivering an equivalent amount of heat as electricity is an order of magnitude less efficient than burning the natural gas directly to heat your food or water. No matter what mumbo-jumbo they're spouting, you still need to expend a certain amount of kilocalories to heat a galllon of water or to cook a dozen eggs.
You want to really save energy and minimize your CF, get a more efficient washer and dryer and keep the gas heater and stove. Get a more efficient gas water heater; current models extract so much of the heat they vent through 2inch PVC.
mnem
:=\
--- End quote ---
If you live somewhere with a civilised amount of sunlight, you can use a solar HWS. Direct conversion of the incident suns rays to heat, which heats your water.
Ours does have a electric "booster", but it is "off" most of the time.
Another bonus of a better climate is that you can dry your clothes on a rotary clothesline in the backyard.
Of course, if you live in "a high rise apartment building" (sales bullshit for a "block of flats"), you are out of luck, as they won't let you hang clotheslines between buildings, except maybe in Hong Kong!
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