Stock Electronic Image FAILS

[vk6zgo]

I've never found a use for such a poorly parameterised transistor tester.

I always thought they were a go/no go check that the transistor works (or not) rather than determining characteristics of it.

They don't really work as go/no-go though because if there's a CE short (at least on the meters I have used) it will show as having a very high gain, 500+, which is in the 'plausible' range for some types of devices.  And CE short is probably one of the more common failure modes for BJTs.

If it pulsed the base it could determine whether the transistor had any shorted junctions, but it doesn't do that. So the utility is very limited IMO -- at best it's a "toy" feature to learn a bit about transistors.

Who really needs a dedicated transistor test socket on a multimeter?

They were a gimmick on the last few generations of analog meters, & remain a gimmick on DMMs.
It is easy enough to test transistors to determine the correct pin configuration & to do "go or no go" tests with the DMM on
"diode test", & using the test leads.

(1) Find the base by testing between the pins until you find a pin that tests as a diode to both of the other pins.
You now also know there are no shorted or open circuit junctions, & whether the device is NPN or PNP.

(2) For simplicity let's assume it is NPN.
Now, placing the +ve & -ve DMM leads on the two unknown pins, moisten your finger & place it between the "+ve" pin & the base.
As BJTs do to some extent work "backwards" even if the +ve pin is the emitter, the DMM will show a reading---record this.
Reverse the +ve & -ve connections & again moisten your finger & place it between base & the "+ve pin".

If this is a higher reading, that pin is the collector, if lower, it is the emitter.
(All polarities should be reversed for PNP).

Of course, such a test is not very repeatable, as a calibrated "spitty finger" is a bit hard to come by, so you can mount a bunch of sockets of various types & have a resistor of several k connected between various configurations of base & collector via a pushbutton switch.

I always found it easier to tack something together "on the day" or just go with the "spitty finger", although I do have one properly made up for TO3 packages from when I had to match some devices in that package.

I know this is a bit elementary, but I thought giving "chapter & verse" would make things clearer for any "noobs" who may be reading it.

[Fungus]

They don't really work as go/no-go though because if there's a CE short (at least on the meters I have used) it will show as having a very high gain, 500+, which is in the 'plausible' range for some types of devices.  And CE short is probably one of the more common failure modes for BJTs.

I think you're supposed to test them with the diode tester before you go to hFe.

But yeah, those things were designed long before very high gain transistors. A gain of 500 is beyond them.

[vk6zgo]

More AC battery testing LOL -

Actually, that's the correct reading for a cheap DMM with half-wave rectified AC ranges. I just checked on one. It's a case of wrong switch position selected rather than false display. 

I tried it and mine jumped around all over the place.

Odd, it worked on my little Skytronic... https://www.eevblog.com/forum/chat/what-did-you-buy-today-post-your-latest-purchase!/msg4160605/#msg4160605  On a reasonably fresh Alkaline AA I got 2.5V reading (one polarity).

I asked the Fluke77 what it thought----it gave a fleeting reading of around 0.170 to 0.2 volts, depending upon which way round I connected the battery.

I dragged out my little "El Cheapo" Digitech clamp meter & tried the same test on its DMM function, & it agreed with the 77.

The 77 can be confused on DC range by unipolar pulsed signals.

I found this out when I was looking at a DC supply derived of an overwind on my Mother in Law's TV Set EHT transformer.
The filter cap had died, but the Fluke read "a bit low" on DC, & only when I looked at it with a 'scope did it become obvious.

Somewhere I have a very cheap analog multimeter I got with a bunch of resistors & stuff 30 plus years ago---it would be interesting to see what it will do with this "battery" test.

[PlainName]

Shouldn't even the cheapest meters be blocking DC on the AC range?

[mendip_discovery]

For those wondering how/why these gopping pictures ever come out.

Well... its a bit like asking an EE to photograph some equipment in use. You end up with a technically correct picture but its messy, disorganised and not much use for stock imagery. How many times have you looked at a Ham Radio club website/magazine and cringed at the photograph they use to show off the kit.

If you are in the stock image market you are trying to get generic and non-brand-specific photos while also doing this on a budget as you might not earn any money from the photo for a while if ever and even if it does get used it might only be a few $£. I have tried to submit photos and got a list back of things that were not much use.

Then you have the sales team and photographer trying to get photos. Think of what level of knowledge a social media influencer has on a subject and put it with a person being paid to get some good looking photos and has even less knowedge of the subject.

I always wince when I look at other cal lab websites as its always the same images, the lab likes to show they have stuff but don't want to give away too much of the kit they have so the competition can get a look in. Look they have the NCC 1701-B, OMG they are soo old skool.

Though my mind boggles with the photos I see on sites where cheap Chinese products are sold. Objects photoshopped into another image but making a mess of scale so you can't actually see the size of it. I see on Kickstarter lots of videos promoting a product using western actors and giving the whole made in the USA vibe but then you look at it and just a Chinese outfit selling some shonky product.

[Gyro]

Shouldn't even the cheapest meters be blocking DC on the AC range?

Should or desirable?  That would require the addition of a reasonably sized series capacitor and at least full wave rectification. You could argue (in fact the manufacturer clearly has!) that sticking in a simple series diode and adjusting the scale factor is good enough for a (sub) cheapie with a 200V lowest AC range.

[PlainName]

Should. It's wrong to give an AC value to a DC signal, although I suppose it could be argued that DC is merely AC with a very long period (but it would have to be really so long it would effectively be DC anyway).

[xrunner]

My advice would be to lose the tranny tester and fix the DC measurement - costs should cancel out. 

[TimFox]

Shouldn't even the cheapest meters be blocking DC on the AC range?

The old-school Simpson 260 analog VOMs had separate modes for "AC" and "Output", where the latter was DC-blocked with a series capacitor.

[RoGeorge]

[xrunner]

The other side is broken? 

[magic]

Looks like he is soldering SMD push buttons on a webcam, good for him.
Where is the fail?

edit
Maybe not a webcam, not sure what it is.

[floobydust]

roasted thumbnail? Well that and he's gonna fail heating up one side of a two pin switch, that does not remove it. Nope. Tried it.

[magic]

Actually, weird things can be desoldered with one iron and some patience and creativity.
In this case, you could nudge each side alternately until both are shifted off their pads.

[Zoli]

Nail and skin touches iron - very fast reaction; don't ask me how I know.

[AndyBeez]

Not sure why this is a thing considered suitable for human use, but we use an identical 'tub-n-spa' to jet wash engine casings and fan shrouds. Which probably explains why the bosses wife is not impressed with our male obsession for gleaming car parts - because she normally uses it to jet wash her dog. Maybe you could use one of these 'porta-pools' to ultrasound oversized printed circuit boards? Anyway, it's a thing (Hot/cold girl and cold/hot soapy water not included).

[helius]

Nothing screams "boutique bathtub" like a giant warning label.

On the other hand, a product I have has a quite reasonable warning:
CHOKING HAZARD. Small children who tamper with delicate parts will be forcibly choked.

[PlainName]

That warning label looks fake to me: different perspective to the tub. Struggling to think why they'd stick a fake label on there, though!

[McBryce]

If the wife ever gets amputated from the waist down, at least I'll know where to get a suitable tub for her.

McBryce.

[Fungus]

If the wife ever gets amputated from the waist down, at least I'll know where to get a suitable tub for her.

Legs are sold separately.

That warning label looks fake to me: different perspective to the tub. Struggling to think why they'd stick a fake label on there, though!

Nah, there's dozens and dozens of pictures of these things out there. Hardly any of them look photoshopped.

[PlainName]

That one does too. The warning label is square on (that is, the horizontals are dead horizontal and the verticals dead vertical) but the surface it is supposed to be on is curved and tilted away slightly. And we're looking at it from just above.

[Nominal Animal]

Not sure why this is a thing considered suitable for human use, but we use an identical 'tub-n-spa' to jet wash engine casings and fan shrouds. Which probably explains why the bosses wife is not impressed with our male obsession for gleaming car parts - because she normally uses it to jet wash her dog. Maybe you could use one of these 'porta-pools' to ultrasound oversized printed circuit boards? Anyway, it's a thing (Hot/cold girl and cold/hot soapy water not included).

I particularly like the blood splatter on the floor.

[Gyro]

I particularly like the blood splatter on the floor.

"Easy home assembly" 

[Ed.Kloonk]

Detachable legs.

Hmm.

[AndyBeez]

Let's do physics... a eureka moment. Actually the tub is big enough for two, provided they are very bendy

I wonder if those fake instructions suggest the bathers change the water between couples? Unlike (Marriott) hotel jacuzzis.

I still prefer the garage application of these. You can use it as a miniature paint spray booth too.

Anyway, it's been a few year's since I studied the laws of thermodynamics, but I'm sure this highly technical diagram illustrates just how these hot tubs are the next best thing to storing radioactive waste in the bidet.