Test Equipment Anonymous (TEA) group therapy thread

[Specmaster]

@mnem I think that the Auto Zero on the 3478A only really works when in V =volts mode by RTM it suggests that each time the probes are open circuit, the meter takes a reading and then subtracts that reading from the reading obtained when the probes are connected to a voltage source.

If you need to get to a zero for resistance readings then you will either need a meter as bd suggested which has a ohms adjust control such as a HP3466A or a Fluke 8012A both of which have the manual adjust pot to zero the ohms reading or a meter such as the Brymen 867 which the delta key.

[beanflying]

                             
Ok morning meditation done, fought for the world revolution, had a second coffee time to go make more MDF dust 

[mnementh]

If you're wondering: from my testing so far, a shorting lead or shorted set of leads measures ~0.1400-0.1800Ω on this meter; so far, I haven't figured out how the "auto-zero" is supposed to work. I really need to read the manual rather than just skimming it like 6 times. 

Well, RTFM is a useful last resort, but that reading sounds about right and in this case I would simply use 4 bits of wire

LOL... I'm totally snurching that.

While I know I AM resourceful enough to build a pair of "semi-kelvin" probes for this thing, that seems a bit convoluted just to get it to come close to zero. I figured the fact I couldn't find some equivalent of Δ or "zeroing" was simple user error. One of the grails I was seeking in the purchase of this unit was the 4-decimal resolution for locating shorts in a PCB.

Ah, that's  a chance to get a new class of test equipment, e.g. a Hytrak 100D. That is designed to measure low resistances (one range is up to 0.2 ). You don't even need to look at the display, since it emulates a mandrake by screaming at you.

Glider pilots have a very similar instrument, the audio variometer, which allows you to know how fast you are going up/down while still keeping an eye on those other aircraft which are (hopefully) a few hundred feet away.

Yeah, I made a ShortSqweek back in the day; which I believe the Hytrak is a direct descendant of, so no stranger to that type of device. I was just looking for something slightly less disaster-prone.

@mnem I think that the Auto Zero on the 3478A only really works when in V=volts mode by RTM it suggests that each time the probes are open circuit, the meter takes a reading and then subtracts that reading from the reading obtained when the probes are connected to a voltage source.

If you need to get to a zero for resistance readings then you will either need a meter as bd suggested which has a ohms adjust control such as a HP3466A or a Fluke 8012A both of which have the manual adjust pot to zero the ohms reading or a meter such as the Brymen 867 which the delta key.

Hmmm... I can turn AZ On/Off in Ω mode, so not sure what it's supposed to do for me there. That's why I figured I needed to RTFM and figure it out.

I guess my point is... the cheapest POS $3 analog meter from 50 years ago had zeroing/lead comp. It's kindof essential to the basic function of the device; why the eff would I NOT expect ANY ohmmeter I buy to have some equivalent?  Should I REALLY expect to have to recalibrate every time I need to use a different probe or change the leads?

Who was the brainchild who decided THIS MODEL didn't need it? Here, let's make a car without any way of fucking steering it while we're doing "Darwin Award-Worthy" engineering decisions... 

mnem
But wait, there's more...

[mnementh]

      

Hmmmmmmmmmm...   Since he worked at HP at the time, maybe his problem was one too many close encounters with the legendary HP P/N 19511-80014... 



mnem
Or maybe one too FEW such encounters... 

[Specmaster]

Hmmm... I can turn AZ On/Off in Ω mode, so not sure what it's supposed to do for me there. That's why I figured I needed to RTFM and figure it out.

I guess my point is... the cheapest POS $3 analog meter from 50 years ago had zeroing/lead comp. It's kindof essential to the basic function of the device; why the eff would I NOT expect ANY ohmmeter I buy to have some equivalent?  Should I REALLY expect to have to recalibrate every time I need to use a different probe or change the leads?

Who was the brainchild who decided THIS MODEL didn't need it? Here, let's make a car without any way of fucking steering it while we're doing "Darwin Award-Worthy" engineering decisions... 

mnem
But wait, there's more...

Yes, I agree with you on that particular point, this meter is meant to be self calibrating once the initial basic calibration has been carried out and in the main it works very well except at these very low resistance values where is some drifting taking place. On the other hand, my Fluke 8840A and 8842A both have an Offset button which does indeed help with the zeroing on the ohms range and using a lead with bananas at each end of 900mm 12ga wire I get the following values by stuffing the lead in the 2 terminal as a short.

HP3478A 0.0234 Auto zero
HP3468A 0.070 Auto zero
HP3466A 0.000 Manual zero
Fluke 8842A 0.002 Manual Offset
Fluke 8840A 0.001 Manual Offset
ITT MX52 0.1 No adjustment
Brymen BM867 0.00 Delta key possible although this reading was without it.
Fluke 27 0.0 No adjustment
Unit-T UT210E 0.0 No adjustment
Robin OM840 0.08 No adjustment
Bside ADM08A 0.0 No adjustment

So the most accurate meter here is the Brymen followed by the 2 Flukes 8840A and 8842A, the HP 3466A is good but like an analog meter, needs frequent adjustments as it drifts a bit.

The HP 3478A is the only one that has 4 digits after the dp and if the zeroing could be improved would be the best for short tracing on boards   

[tggzzz]

I guess my point is... the cheapest POS $3 analog meter from 50 years ago had zeroing/lead comp. It's kindof essential to the basic function of the device; why the eff would I NOT expect ANY ohmmeter I buy to have some equivalent? 

The ohms cal pot was principally to compensate for the changing voltage from zinc-carbon cells.

Should I REALLY expect to have to recalibrate every time I need to use a different probe or change the leads?

... or apply different pressure at the joint between the probe and UUT, or cut through any oxide or dirt or oil films etc.

Four wire Kelvin attachments aren't used because they are cute.

[mnementh]

I guess my point is... the cheapest POS $3 analog meter from 50 years ago had zeroing/lead comp. It's kindof essential to the basic function of the device; why the eff would I NOT expect ANY ohmmeter I buy to have some equivalent?

The ohms cal pot was principally to compensate for the changing voltage from zinc-carbon cells.

Should I REALLY expect to have to recalibrate every time I need to use a different probe or change the leads?

... or apply different pressure at the joint between the probe and UUT, or cut through any oxide or dirt or oil films etc.

Four wire Kelvin attachments aren't used because they are cute.

Oh, for corn' sake... of course the pot was for both battery and lead comp. The manuals for oodles of such meters explicitly include statements to this effect.

Of course a Kelvin connection is more accurate... but that doen't mean it is the BEST for any given scenario. It is ALSO not the ONLY way this meter was intended to be used, or it wouldn't have a 2-wire function. The fact it does both is somehow an excuse for NOT including adjustment essential to one feature?

Come on man... that omission herein clearly harms the existential usefulness of this meter. It would be foolish to argue otherwise.

mnem
Of course it does, as has been suggested, serve quite well to feed the TEA... 

[beanflying]

You know all those times when you chopped off and binned those stupid non (insert your country) plugs off your spare IEC leads.  Lucky I had one only left.....

If it helps you mnementh my Advantest on 4W was off zero too. At least until I punched the Null button 

Much happier with a fixed 100V than a variac bonus is it won't fit Aussie plugs so providing I leave my solitary round pinned IEC it will reduce the chances of a 240V or slip of the variac internal kaboom.

For a simple cheap and cheerful Chinese the step down transformer is not to bad at all internally.

[bd139]

Measurement truth: You can screw up a 4W measurement as bad as a 2W measurement. All the magic past a bit of maths happens after the junction point on the kelvin clips rather than after the junction point inside the meter as in a 2W measurement.

V=IR. delta V is the same if I (current source) is constant and R is constant. I changes with range and R changes with contact and lead resistance. So if you use decent leads with constant R on a meter with little resolution to pick up thermal effects (like the 8012A) and keep it in the same range, null out V then you’re in the same business as the 2W guys for £20

On the 8012A you can drag the leads around on some blank (and abraded and solvent cleaned FR4) and watch the resistance. It’s quite interesting. Might make a video on that.

Also in this non-discretised universe everything is a bastard somewhere if you go looking. Look at that flamewar between Electroboom and professor Ego is a fine example 

[beanflying]

Very true. Ground loops and strays anythings interfere at low resistances and voltages even if their sum in that loop is zero 

https://youtu.be/yfl6Lu3xQW0

[mnementh]

"...spitzen-spartin'-fillibartin' frickin'-frackin' dirty ratzenfratzin butt-ugly son of a 3-toed copper-bottom fool..."

"Ham-fisted Shrek hands" strikes again... a slip of the grip just turned a $120 iPad Air 2 into A $220 one. 

Looks like I fixed the charging issue; believe it or not, it appears there was a screw missing from the battery connector from the factory on this one.

But even taking as much care as I could muster, I still managed to slip and nick a corner of the LCD with my guitar pick while disassembling. Now the display has "terminal plaid". 

Got a new one on the way; hopefully here before Christmas, as I bought from a vendor in Tejas. So now I just have to wait. 

mnem
 

[Cubdriver]

I really need to excavate mine from the rack, pop it open and check the battery.  It's probably due...

Thanks for the nice photos, xrunner.

-Pat

You should, you really should!  I'll remind you if we don't see it in a few weeks.

The thing is really long, but I think I have managed to make a place for it on the bench by creatively re-arranging a corner. Might even run a 10 MHz ext. reference to it (I did test that and it works well).

Yeah, isn't it?  You look at that little front panel and think 'oh, what a cute little sig gen'.  Then look more closely and realize it's about three times as long as it is wide!  Amazingly, I haven't ever taken the cover off of mine.  <hangs head in shame>

-Pat

[tautech]

"...spitzen-spartin'-fillibartin' frickin'-frackin' dirty ratzenfratzin butt-ugly son of a 3-toed copper-bottom fool..."

"Ham-fisted Shrek hands" strikes again... a slip of the grip just turned a $120 iPad Air 2 into A $220 one. 

Looks like I fixed the charging issue; believe it or not, it appears there was a screw missing from the battery connector from the factory on this one.

But even taking as much care as I could muster, I still managed to slip and nick a corner of the LCD with my guitar pick while disassembling. Now the display has "terminal plaid". 

Got a new one on the way; hopefully here before Christmas, as I bought from a vendor in Tejas. So now I just have to wait. 

mnem
 

3 penis fingers has to be better than 5 ! 

Oh, how we learn from our stuff ups....especially when they cost ! 

And you can't fuse that display together with a short puff of dwagons breath ? 

[bd139]

"...spitzen-spartin'-fillibartin' frickin'-frackin' dirty ratzenfratzin butt-ugly son of a 3-toed copper-bottom fool..."

"Ham-fisted Shrek hands" strikes again... a slip of the grip just turned a $120 iPad Air 2 into A $220 one. 

Looks like I fixed the charging issue; believe it or not, it appears there was a screw missing from the battery connector from the factory on this one.

But even taking as much care as I could muster, I still managed to slip and nick a corner of the LCD with my guitar pick while disassembling. Now the display has "terminal plaid". 

Got a new one on the way; hopefully here before Christmas, as I bought from a vendor in Tejas. So now I just have to wait. 

mnem
 

Been there. I sympathise. I’ve bust the screen on my MBP twice. First time I fell asleep and it slid off my lap, second time I dropped it putting it into the bag. That’s $500 a go just for the lid assembly. Then the frigging charger exploded.  Take a deep breath and continue the fight is all you can do.

I got AppleCare on my new one which limits two repair events in 3y to around $100 each. Figured I might need it this time 

[Specmaster]

"...spitzen-spartin'-fillibartin' frickin'-frackin' dirty ratzenfratzin butt-ugly son of a 3-toed copper-bottom fool..."

"Ham-fisted Shrek hands" strikes again... a slip of the grip just turned a $120 iPad Air 2 into A $220 one. 

Looks like I fixed the charging issue; believe it or not, it appears there was a screw missing from the battery connector from the factory on this one.

But even taking as much care as I could muster, I still managed to slip and nick a corner of the LCD with my guitar pick while disassembling. Now the display has "terminal plaid". 

Got a new one on the way; hopefully here before Christmas, as I bought from a vendor in Tejas. So now I just have to wait. 

mnem
 

Looking like we have a second "penis fingers" in the group now 😁

[beanflying]

"...spitzen-spartin'-fillibartin' frickin'-frackin' dirty ratzenfratzin butt-ugly son of a 3-toed copper-bottom fool..."

"Ham-fisted Shrek hands" strikes again... a slip of the grip just turned a $120 iPad Air 2 into A $220 one. 

Oopsy 

I have been paranoid playing with a circular saw and no proper table to fix timber bits to over the last few days. So far all fingers, toes and other appendages are still attached 

Next time your S.O. complains about the space your test gear takes up start building a cave for your 300x300 3D printer (the box needed is about 800x600x700) 

[med6753]

"...spitzen-spartin'-fillibartin' frickin'-frackin' dirty ratzenfratzin butt-ugly son of a 3-toed copper-bottom fool..."

"Ham-fisted Shrek hands" strikes again... a slip of the grip just turned a $120 iPad Air 2 into A $220 one. 

Oopsy 

I have been paranoid playing with a circular saw and no proper table to fix timber bits to over the last few days. So far all fingers, toes and other appendages are still attached 

Next time your S.O. complains about the space your test gear takes up start building a cave for your 300x300 3D printer (the box needed is about 800x600x700) 

That's some nice wood panels you got there. Must have cost a bundle. 

[beanflying]

Nah single sheet of 18mm MDF is cheap. under $40 AUD the perspex for the doors were $30 however.

[tggzzz]

Looking like we have a second "penis fingers" in the group now 😁

Oh, I know we have more than that, but they aren't prepared to admit it.

Oops

[tggzzz]

Measurement truth: You can screw up a 4W measurement as bad as a 2W measurement. All the magic past a bit of maths happens after the junction point on the kelvin clips rather than after the junction point inside the meter as in a 2W measurement.

V=IR. delta V is the same if I (current source) is constant and R is constant. I changes with range and R changes with contact and lead resistance. So if you use decent leads with constant R on a meter with little resolution to pick up thermal effects (like the 8012A) and keep it in the same range, null out V then you’re in the same business as the 2W guys for £20

On the 8012A you can drag the leads around on some blank (and abraded and solvent cleaned FR4) and watch the resistance. It’s quite interesting. Might make a video on that.

Very true about screwing up measurements.

Providing we aren't in the voltnut territory, contact resistance/variability and lead resistance will be more important than seebeck effects.

Voltnut territory can be entered by wanting high resolution and/or low currents/voltages.

[Mr. Scram]

I just reported some spam elsewhere on the forums for

plastic surgery.

I kid you not. I guess the outside world is done with our ugly mugs!

[beanflying]

Useful if any of us chop bits off or need a lengthening procedure 

[med6753]

I just reported some spam elsewhere on the forums for

plastic surgery.

I kid you not. I guess the outside world is done with our ugly mugs!

I'm quite happy with my ugly mug thank you very much. 

One morning I came across some clown who posted real porn.    Turns out Dave himself was logged on and I sent him a quick PM and it was gone in a flash and I think the user joined the band. 

[bd139]

This seems to happen around Christmas. All the idiots come out and shitpost porn on here.

Then again Wikipedia page for Thanksgiving had an unexpected sausage display a while back 

I have been on the Internet too long to even raise an eyebrow now. I've seen things that'd surprise a Vietnam vet now living in a dodgy bit of Thailand.

[beanflying]

I used to have a few 'interesting' customers back in the days of having a real job. Had to watch out for Ping Pong balls in your glass at one of them