Test Equipment Anonymous (TEA) group therapy thread

[Vgkid]

Here are their specs , one is missing a binding post.

[GregDunn]

Sinclair's version of RPN was cost optimised as was everything he did. Which is why it was poo. HP41 was faaaar nicer than anything else on the market. But more expensive. I was a user of HP calculators for many years.

Edit: dammit now looking on ebay for an HP-41CX

Did someone say HP calculators?  These are just the ones in the office upstairs...

[bitseeker]

Cool! I still have the HP 28S I used in EE classes. It uses those funky N-size cells and not 2, nor 4, but 3 of them.

[bitseeker]

Announcement: The "Jammy Git" award image has been iconized and added to the Post Icons section of the OP for your convenience. Jammy Git award description by mnementh.

[Carl_Smith]

Did someone say HP calculators?  These are just the ones in the office upstairs...

Well you have me beat.

I started out with an HP28S, but it only lasted a few years until it succumbed to hard use and a bit of abuse.  Then I got an HP48GX.  Used it for a couple decades until some years back I happened to find an HP 48gII at a pawn shop for $40.  It has a bigger screen that is easier to read.  But I never liked that the Enter key is in the wrong spot (lower right).  But it is so much faster than the 48GX that I can't really stand to use the 48GX anymore.  And a couple years after getting the HP48GX I had a need to do a lot of financial calculations and I got tired of programming finance formulas into the 48GX and bought an HP 17BII Business calculator.

Back when I got the HP28S somewhere around 1988, it took a while to get used to the RPN way of doing things.  But once I did it seemed like the only right way and the only way that made sense anymore.  I became almost unable to use a normal calculator anymore.  But in recent years I've been using the HP calculators much less and using other random calculators I happen across and I've actually learned how to use a normal calculator again.   

EDIT: Stupid phone took the picture upside down, and I rotated it in the Win10 picture viewer, but apparently the forum didn't recognize that and I had to load it into a real editor and rotate it.

[Carl_Smith]

Cool! I still have the HP 28S I used in EE classes. It uses those funky N-size cells and not 2, nor 4, but 3 of them.

And thereby wasting 25% of all the N Cells you buy because they come in 2 or 4 packs and you can never find the spare one next time you need to change the batteries.

[Housedad]

I never did like Reverse Polish Notation.  I stayed away from the HP's since the 90's because of it.  It just never seemed right to me.

[GregDunn]

When I was in college, no joke, we all used slide rules because there was no such thing as a usable pocket calculator until the early 70s when HP started the trend.  A couple of well-heeled friends bought HP35s and started taking them to class (in those days, $400 was about a month's wages for a new engineer, let alone a starving college student).  They were so much faster than the slide rules that all the departments had to institute new requirements to prevent the lucky ones from blowing the rest of us away during tests.  Until calculators dropped enough that we could all afford one, the law was generally "no calculators on tests"; in fact, some of the professors set up the calculations so that there was little to no advantage in using one except for precision.  The goal was teaching engineering, not number crunching.   

But enough people were carrying the HP35/45 by 1973 that I had plenty of chance to use one.  We had a couple of impromptu demos where a group would try to solve chained calculations (circuit meshes, chemical conversions, etc.) using AOS and RPN calculators; invariably the RPN users were able to outrun the others, and that decided me.  After a little familiarization, I realized that the standard non-stack-based calculators actually wasted keystrokes, and if you needed an intermediate calculation's results, you lost a keystroke or two every time you had to access it.  With the HP, you could just take numbers as they were given to you and keep calculating.  Think you need another intermediate result level?  Just hit Enter again, and if it wasn't necessary you didn't have to decrement the stack. 

The early calculators which attempted to substitute parentheses for the stack were a real kludge - they expected you to know how many levels the calculation was going to require before you started - or write it down first.     Plus, different brands did different things with the "=" key that affected how you completed a calculation.  Admittedly, arithmetic calculators have gotten better since 1972, but the stack-based HP architecture is still as natural today as it was then.  Part of the reason I still have all my HP calculators is that I prefer RPN when I'm doing work even today.  I still have my Post Versalog too, but more as a reminder of how far we've come.     Incidentally, slide rules (if you used them efficiently) behaved very much like a stack-based calculator.  If you used the C and CI (or D and DI) scales alternately, it saved a step for every calculation in a chain...

[Berni]

And by the time i got to university we had TI N-spire CAS calculators. Unlike the older graphical calculators this one is smart enough to take your math problem in any form you want as long as it makes sense. Your unknown variables can be scattered all over the equation and it simply solves for the one you want. Multiple such equations can simply be tied together to form a system of equations. If you want a solution where one of the complex unknowns has no imaginary component you simply tell it "Im(x)=0" and add that as an equation and it will solve it at the push of a button.

I could never get the old HP calculators to do anything useful apart from using it as a glorified scientific calculator.

[tggzzz]

I never did like Reverse Polish Notation.  I stayed away from the HP's since the 90's because of it.  It just never seemed right to me.

Most non-RPN calculators were actually half-RPN. For example, to calculate sin(30+5) the keystrokes are 30 + 5 = sin

Lots of non-RPN calculator still get basic arithmetic wrong, e.g. 1+2*3= gives 9 when it is actually 7.

Besides, I like the concept of "gather your ingredients, then do something with them", as opposed to "get one ingredient, prepare to do something with them, get the other ingredient".

[bd139]

Good memories here

I don’t actually use an RPN calc now. I had a 50g for a few years towards the end of my HP times but decided that I didn’t need it. It was true. The Casio FX 991 EX does pretty amazing things for £20 and has a very decent entry system, arguably better than RPN. To quote tggzzz it allows you to gather all your ingredients up front. And it is forgiving of mistakes.  I have flirted with the idea of a higher end Casio unit as the programming language on those fits in your head unlike RPL. That would mean I can knock up some simple programs rather than have to dig out the laptop and then get distracted here 

Someone actually gave me an earlier B&W TI nSpire CAS. That was bloody awful. If you left it for a couple of days you’d have to wait for it to boot up.

[URI]

Announcement: The "Jammy Git" award image has been iconized and added to the Post Icons section of the OP for your convenience. Jammy Git award description by mnementh.

When mnementh awarded me the jammy git I googled and found a discription at en.wiktionary.org: "a "jammy git" would be a person with undeserved luck."
Hmm. Wasn't sure about the level of irony mnementh put in there..   

But with that description I take pride in being "Jammy Git" awarded.   

I'm also seeing forward to the Jammy Git being awarded again, cause it's fun to me also.   

[bd139]

I think jammy git is basically the opposite of schadenfreude

[Specmaster]

Announcement: The "Jammy Git" award image has been iconized and added to the Post Icons section of the OP for your convenience. Jammy Git award description by mnementh.

When mnementh awarded me the jammy git I googled and found a discription at en.wiktionary.org: "a "jammy git" would be a person with undeserved luck."
Hmm. Wasn't sure about the level of irony mnementh put in there..   

But with that description I take pride in being "Jammy Git" awarded.   

I'm also seeing forward to the Jammy Git being awarded again, cause it's fun to me also.   

Wear the award with pride, I believe I was the first recipient and held it more than once but by the sound of it it's going to be hard to win it back again in the future [emoji106]

[GregDunn]

Most non-RPN calculators were actually half-RPN. For example, to calculate sin(30+5) the keystrokes are 30 + 5 = sin

Lots of non-RPN calculator still get basic arithmetic wrong, e.g. 1+2*3= gives 9 when it is actually 7.

Besides, I like the concept of "gather your ingredients, then do something with them", as opposed to "get one ingredient, prepare to do something with them, get the other ingredient".

This.

I think that's why RPN seemed to be most comfortable to me and most of my fellow students; at the very least it was consistent and the operation comes (as it should) at the end of the sequence.  I think too many people are/were fixated on the written appearance of a math equation instead of the actual process you use to solve it; you don't add or subtract (or any other binary calculation) before you have both numbers in place.  When we see a written equation we actually group the operands mentally rather than step from left to right - at least once we are familiar with the process.  AOS calculators always seemed to require you to reduce the equation in your head first before entering it - effectively converting it to stack calculations anyway.

And again, things have improved since 1972.  But given the low complexity and speed of the early calculator chipsets, that sort of advanced processing just wasn't available at the beginning.  You could do things with an HP35 that took a little more sophisticated programming to accomplish with other calculators - at least for quite a while.

[bd139]

Fortunately no longer an issue with natural display stuff. Enter it same as book. This has the advantage that you can validate your calculation before you execute it. Also easier to change than half way through a stack of RPN commands.

[Cerebus]

I love it when I am actually good for something instead of good for nothing!!

Quick, quick, show it to your SWMBO's Mother! 

[Cerebus]

When I was in college, no joke, we all used slide rules because there was no such thing as a usable pocket calculator until the early 70s when HP started the trend. 
...
 in fact, some of the professors set up the calculations so that there was little to no advantage in using one except for precision.  The goal was teaching engineering, not number crunching.   

One of the advantages of using a slide rule is it drives home, or should, the fact that you are losing precision at each calculation. Use a calculator, or a computer, and it's easy to forget that those too are subject to the same rules of finite arithmetic and lose some precision at each calculation albeit more slowly (in most circumstances). Use a computer, so that you can do a calculation a few million times, and those minute errors can turn into a big error. I've seen it trip people up, more than once. There are whole textbooks on the subject of "how not to foul up calculations using finite arithmetic" aka Numerical Analysis.

[bd139]

We're mostly engineers though. Round this, truncate that, solve this, solve that, hey that's good within a few percent, wing it. Oh it works well enough

We just want the world to know that we use laplace and slipsticks

[Berni]

So that works out to.. 264.66 Ohm... well i got a 220 Ohm in my box of resistors, that will do.

[bd139]

Or 270 if you have a full E12 kit or 47+220 in series if you're really pedantic

Real engineers are lazy as fuck. Python program that finds resistors based on what you can be bothered to stock thus avoiding all effort more than once:

Code: [Select]

#!/usr/bin/env python

import itertools
import sys

# Stock resistors - enter yours here
stock = [ 10, 22, 47, 100, 220, 470, 1000, 2200, 4700, 10000, 22000, 47000, 100000, 220000, 470000, 1000000, 10000000 ]

def straight(of):
    """Return list of straight values"""
    for i in stock:
        yield (i, "{0} = {1}".format(i, i))

def parallel(of):
    """Return parallel combinations of values"""
    for i in of:
        for j in of:
            par = 1.0/(1.0/i + 1.0/j)
            yield (par, "{0} || {1} = {2}".format(i, j, par))

def series(of):
    """Return series combinations of values"""
    for i in of:
        for j in of:
            ser = i + j
            yield (ser, "{0} + {1} = {2}".format(i, j, ser))

def closest(to, collection):
    """Return closest value"""
    return min(collection, key=lambda x:abs(x[0]-to))

def main():
    if len(sys.argv) == 1:
        print("Usage: rcomb value")
        sys.exit(-1)
    inval = float(sys.argv[1])
    combos = itertools.chain(series(stock), parallel(stock), straight(stock))
    close = closest(inval, combos)
    closeval = close[0]
    dist = closeval / inval if inval > closeval else inval / closeval
    print("{0} -> {1}%".format(close[1], (1 - dist) * 100))

if __name__ == "__main__":
    main()


[mnementh]

mnem
that is all.

[med6753]

Real engineers are lazy as fuck.

You got that right. Which means us lowly technicians have to figure it out and sort through the mess. 

[Carl_Smith]

mnem
that is all.

Python seems to be a good language for getting things done quickly and I've been intending to learn it for a long time now but I never get around to it.

But I think it's kind of ironic that python fans brag about being able to do "Hello World!" in one line.  Seems to me we could all do that back in the 1980's with any computer that booted right into BASIC, or any computer that had a BASIC interpreter.   

This is my favorite way to do a Hello World program:

[Ice-Tea]

Real engineers are lazy as fuck.

I once found this quote in a book on Digital Electronics:

Nothing Dignifies labor so much as the saving of it.

A rule I try to live by.