Test Equipment Anonymous (TEA) group therapy thread

[med6753]

So I replaced that RIFA. PSU board was easy and quickly to remove from the scope. Paid extra attention to plastic rod operating the mains switch, since you said it could break easily... got lucky, it came out and back on, with no drama 

You put a Rifa cap back into the unit!?  I hope you got a late date code on that part............... 

It was new stock Kemet from Mouser. Probably as good as it gets. (Kemet bought RIFA from Evox who bought it from Ericsson who bought it from its competitors back in the late 50s when there was capacitors on the world market again.  RIFA is short for "Radioindustrins Försörjningsaktiebolag" (Radio Industries Supply Company) and was a joint venture between Ericsson, ASEA, AGA and possibly some more, to build components in Sweden during WW2. )



(Trade rag advert from the late 1950s)

I always though Swedish Bombshells were.....



In reality they are this....



I r disappointed. 

[DC1MC]

So I replaced that RIFA. PSU board was easy and quickly to remove from the scope. Paid extra attention to plastic rod operating the mains switch, since you said it could break easily... got lucky, it came out and back on, with no drama 

You put a Rifa cap back into the unit!?  I hope you got a late date code on that part............... 

It was new stock Kemet from Mouser. Probably as good as it gets. (Kemet bought RIFA from Evox who bought it from Ericsson who bought it from its competitors back in the late 50s when there was capacitors on the world market again.  RIFA is short for "Radioindustrins Försörjningsaktiebolag" (Radio Industries Supply Company) and was a joint venture between Ericsson, ASEA, AGA and possibly some more, to build components in Sweden during WW2. )



(Trade rag advert from the late 1950s)

I always though Swedish Bombshells were.....



In reality they are this....



I r disappointed. 

Did you see one of the other Swedish bombshells explode, the little smoke puff and sparks of a RIFA is nothing in comparison. 

[Specmaster]

l

Naaahhh... you're not wrong. Characterizing noise is one of the areas that, IMO, a good analog scope still excels at and in many ways beats out a DSO. In this scenario, it does the averaging by dint of its inherent nature. You don't need the absolute detail that digitizing gives you; you just want to see where the fuzz is thickest and where it ends.

Amaze youngsters by using an analogue scope to quickly and easily measure the RMS value of wideband noise.

At amaze them with an HP 3400A which is even easier

Talking of which I need one of them to measure noise figure on something.

OK. Go on. Do that by the end of the week, rather than at some indefinite time in the future

Considering I don’t have any analogue oscilloscopes at the moment I shall defer until some indefinite time in the future

A clear demonstration of how unwise it is to dispose of anything.

Theres a compromise somewhere there.

Actually if I’m remembering how to do it properly it might be possible to do it with intensity grading or persistence on the Siglent. I will have to make a noise source and try it. After I’ve moved!

That is why the combiscope is such a great unit, got the best of both types in the single case.

[Robert763]

<snip>
AirPods pro with transparency mode on. Also works for the idiots when you get out of the car as you can turn on noise cancellation mode 

Not so sure that they are allowed to be used while driving, certainly not worth the hassle of trying to explain to traffic cops that you can still hear emergency two tone horns and other shit.

Fair points. I don't drive with them in as I quite like offensively loud music so I can't hear the two tone horns either 

I can join you on that point, I love to play my stereo loud and soak in all that lovely sound quality 

I rarely listen to music while driving. I find it too distracting. I much prefer to be fully alert for hazards as well as concentrate on the main objective: driving.

I'm the other way. I find having music on helps me concentrate on driving. with noting on my mind tends to drift to other subjects.....

[tggzzz]

*puts hand up to ear*   "WHAAAAAAAT?!?"

mnem
thump.

Just today I'm coming up my road and there is a kid on a bicycle going in my direction in the middle of the road. I slowed and figured he would hear my approach. Nope. I had to come almost to a complete stop and decided I had no choice but to lay on the horn. Only then did he turn around and realize I was there and moved over. And then I saw that the jerk had earbuds on. 

Today, within 200 yards:

Police car making a three point turn across a busy, narrow, main road while his vision is blocked both ways, including hitting the kerb while he was reversing, this is him hitting the curb



woman on a pushbike stopped inside a traffic light controlled junction to play with her mobile,




man steps out into the road in front of me, without looking, 10 yards from a zebra crossing he could have used instead,



OK, who fitted the idiot magnet to my car?

What.. I think you did that, I think that has become the most commonly used phrase by BMW, Volvo and Audi drivers at least here in the UK 

s/by/about

And no, I don't know vi(le) commands beyond x dd dw i a A

[mansaxel]

If I listen to this while driving I can guarantee myself a speeding ticket. 

I have mixed monitors during that song. With original vocalist. Twice. Very nervous, but it went well. A very good FoH engineer (with the band) helped me out a lot with learning the bands desires.  I very much remember the phrase: "Gillan does not use wedge monitors". Sidefills only that was.

Code: [Select]

22.03.92     Helsingborg Caesar's Palace, Sweden
26.03.92     Helsingborg Caesar's Palace, Sweden

(from http://www.gillan.com/gigography.html#1992 )

[bd139]

Quick experiments on measuring noise. Excuse the crap photos - they are phone ones and the curtains are shut and the light off.

Output DG811 noise 1V RMS into 50R. I'm not sure what the noise power/bandwidth relation is on this.

Well firstly I did the old two signal thing and tried to overlap them until there is no peak as you do with an analogue scope. That did not work because the channel display of the active channel completely overlays the other one rather than adds to it.



If you turn off intensity grading it is more profound:



Now if you do one channel and measure the RMS voltage it comes out at 0.666 volts.

Let's try the 34401A ... 0.123 volts



Now the 3465A ... 0.145 volts.



Worth noting that the RMS figures might actually be fairly accurate as the "noise power" is proportional to bandwidth. The 34401A is true RMS responding with about 1MHz of bandwidth (measured). The 3465A is average responding with about 800KHz of bandwidth (measured) but peaks slightly above the first dip so that might explain that. The scope is, well 200MHz in theory so that's going to read a lot more.

So conclusions:

1. Digital scopes are shite for measuring RMS noise using traditional methods.
2. They might be ok using direct RMS measurements but that would need validating.
3. Buy a power or RMS voltmeter with thermal RMS sensor and an analogue scope
4. Noise is difficult to measure and you must consider instrument bandwidth.

Further experiment: Develop a passive 50 ohm low pass filter that is under the bandwidth of all instruments and has close to zero insertion loss thus equalising and measure again on all devices.

Edit: 5th order chebyshev LPF should do the job...

[tggzzz]

I expected that would be the case with a cheap Siglent/Rigol/etc. I don't know whether it would be the same with a more expensive scope where adverts show it doing eye diagrams.

A key test might be whether or not you can change the opacity of a trace, or whether adverts show overlapping traces (which I find usegful sometimes).

[bd139]

I expected that would be the case with a cheap Siglent/Rigol/etc. I don't know whether it would be the same with a more expensive scope where adverts show it doing eye diagrams.

A key test might be whether or not you can change the opacity of a trace, or whether adverts show overlapping traces (which I find usegful sometimes).

One for another day. Added to the notebook however.

[Brumby]

just did the bloody COVID test. Rats, it's positive and I feel rotten ...

Oh crap. 

That was my first reaction too.

Take care ... Get better soon.

[AVGresponding]

Stupid question for the gang.
If a water electro-valve spec is 24VAC, can I use VDC to control it?
If yes at what voltage DC current?

Yes I am a little embarrassed to ask....

I'm with the Capt.Bullshot here. Basic answer is NO.

Why even try such?
As for someone suggesting that it had been tried with a contactor: I've seen and smelled a control cabinet where someone 'tried' that with around 50 contactors. You could not touch them even at the top plastic around the contacts and it stank like a fire in waiting.

Probably because they used 24VDC instead of 12V and it cooked the coil? You might try it if you didn't have easy availability of 24VAC.

Also, what difference does it make to the contacts, whether you use the correct voltage or not? Only thing I can think of is the DC voltage was too low and the contact pressure was therefore low and the switched load was close enough to maximum that it caused excess arcing?

In any case, a control valve wouldn't have that issue. If the valve has a VA rating, just measure the coil DC resistance, that'll tell you the necessary DC voltage if you really want it spot on.

Nope. It was definitely 24V AC contactors fitted into a 24V DC system. I investigated that at a VW factory because a junior colleague called for aid. It was in 1991 during a complete refit of the famous Halle 54 and I was doing PLC coordination for the major electrical contractor of VW, a company named Velte Electric.  I have no idea how he missed that stench and the unnormal heat. Those contactors were never intended to fit in those cabinets. Either a really dumb subcontractor ran out of contactors or some event had the Aushilfslagerjunge act in the absence of someone knowledgeable - this part did not make it to me. I was subsequently given a list of all cabinets supplied by that subcontractor and we found one more like it, which was not yet energised.
It did nothing to the contacts, but the plastic housings of all those contactors were too hot to touch FROM THE COIL.

Ah, well, there you go. 24VDC is far too high for a 24VAC coil. Now you've got me wanting to dig out a 24VAC relay to measure the coil resistance and work out the DC voltage required. Like I said before though, I've used 24VAC relays on a 12VDC system before now without issues, though my guess is the optimal DCV is somewhere around 16.8   

[Robert763]

Naaahhh... you're not wrong. Characterizing noise is one of the areas that, IMO, a good analog scope still excels at and in many ways beats out a DSO. In this scenario, it does the averaging by dint of its inherent nature. You don't need the absolute detail that digitizing gives you; you just want to see where the fuzz is thickest and where it ends.

Amaze youngsters by using an analogue scope to quickly and easily measure the RMS value of wideband noise.

At amaze them with an HP 3400A which is even easier

Talking of which I need one of them to measure noise figure on something.

I've a spare Fluke 8920........

[Kosmic]

I expected that would be the case with a cheap Siglent/Rigol/etc. I don't know whether it would be the same with a more expensive scope where adverts show it doing eye diagrams.

A key test might be whether or not you can change the opacity of a trace, or whether adverts show overlapping traces (which I find usegful sometimes).

Not working on my Lecroy WavePro 960. The traces don't blend in Persistence mode. Channel 1 is always on top of Channel 3.

[AVGresponding]

Easier just to link this Omron datasheet.  https://www.mouser.co.uk/datasheet/2/307/ly_ds_e_4_8_csm54-1291204.pdf

You can see the 12VDC coil resistance is very close to the 24VAC coil DC resistance. The result of powering the 24VAC relay coil with 12VDC will be slightly more current, but slightly less VA.

I couldn't find any of my boxes (yes plural) of industrial relays, I suspect they my be buried under other stuff...  I did find a box of industrial control gears which I'd forgotten I had, there's an IMO 24VDC DIN rail psu, which I shall test to see what the output is like...

[Robert763]

Stupid question for the gang.
If a water electro-valve spec is 24VAC, can I use VDC to control it?
If yes at what voltage DC current?

Yes I am a little embarrassed to ask....

I'm with the Capt.Bullshot here. Basic answer is NO.

Why even try such?
As for someone suggesting that it had been tried with a contactor: I've seen and smelled a control cabinet where someone 'tried' that with around 50 contactors. You could not touch them even at the top plastic around the contacts and it stank like a fire in waiting.

If it is a valve, then I'd also say NO. Relays and contactors could be made suitable if a spare N/C auxiliary contact exists on them or can be added (preferably a late break one) with a suitable resistor connected across it and in series with the coil. The reason for this is to limit the current that flows through the coil once energised as the coil will overheat without it and either burn out, or the plastic bobbin will melt and cause the magnet assembly to jam up rendering the relay/contactor inoperable. Most coils are wound for AC supplies and the impedance of the coil restricts current flow, but with DC, there is no impedance factor / back EMF being applied to the current flow and hence the need to control that aspect once the relay / contactor has closed.

See my much earlier response. DC is fine with no resistor as long as the appled DC loatage gives the same or slightly less than the original RMS AC current. AC relay coilss stil have resistance, measure it and use I x R to find the required voltage.
Putting 24V DC will overload a 24VAC relay or valve and let smoke out....

Edit: posts crossed.
VA does not matter for DC other than coil heating. You can use a relay quite happliy as a current operated switch, the just tend to have a high burden voltage.

On the other hand I've just been running a 28V DC contactor off a 115V 400Hz supply without any resistors, zenners or voltage regulators.  Any guesses?

[tggzzz]

I expected that would be the case with a cheap Siglent/Rigol/etc. I don't know whether it would be the same with a more expensive scope where adverts show it doing eye diagrams.

A key test might be whether or not you can change the opacity of a trace, or whether adverts show overlapping traces (which I find usegful sometimes).

Not working on my Lecroy WavePro 960. The traces don't blend in Persistence mode. Channel 1 is always on top of Channel 3.

Thanks. I'm not entirely surprised.

What happens in any of the non-persistence modes? Can you overlay two traces?

[Kosmic]

I expected that would be the case with a cheap Siglent/Rigol/etc. I don't know whether it would be the same with a more expensive scope where adverts show it doing eye diagrams.

A key test might be whether or not you can change the opacity of a trace, or whether adverts show overlapping traces (which I find usegful sometimes).

Not working on my Lecroy WavePro 960. The traces don't blend in Persistence mode. Channel 1 is always on top of Channel 3.

Thanks. I'm not entirely surprised.

What happens in any of the non-persistence modes? Can you overlay two traces?

Yes you can set the traces transparent and they will blend.

[Vince]

If anyone might be interested, there is a Nixie DMM that just popped up here, for only 20 Euros.

3 digits made by Schneider, model " DIGITEST 500 ",  and a compact portable unusual form factor, to add to your collection.

Seller says local pickup but it's not worded too strongly so he might be willing to ship if just asked   


https://www.leboncoin.fr/bricolage/2159083354.htm

[Cerebus]

Might be just us, but around here electricity is so cheap it would only make sense to install solar panels if you can't get connected to the grid.

It is just you. Most of us in most of the rest of the world don't have "hydro" as part of the local power company name.

[Cerebus]

Actually if I’m remembering how to do it properly it might be possible to do it with intensity grading or persistence on the Siglent. I will have to make a noise source and try it. After I’ve moved!

Easy. Microphone + pin + No. 2 Daughter = broadband noise. 

[Cerebus]

My actual 2022 top most played on Apple Music is embarrassing so I won’t post it here 

All the Best compilation from Engelbert Humperdinck, Barry Manilow and Dean Martin¹?

 


¹ covered by Leo Moracchioli

Worse

https://youtu.be/rRncgJhNf-k

Click on this link at your own risk!

I hear that the Musician's Union have issued a fatwa against you just for posting that link.

[Cerebus]

My actual 2022 top most played on Apple Music is embarrassing so I won’t post it here 

All the Best compilation from Engelbert Humperdinck, Barry Manilow and Dean Martin¹?

 


¹ covered by Leo Moracchioli

Worse

https://youtu.be/rRncgJhNf-k

Click on this link at your own risk!

Ok not that bad. That is NSFW 

OMG. 3 minutes of my life wasted. 

The thing that worries me is that, while I held out for perhaps 10 seconds, you hung around for 3 minutes.

[TERRA Operative]

You put a Rifa cap back into the unit!?  I hope you got a late date code on that part............... 

I did that with several in my HP8562 spectrum analyser. As with everything in that mechanical marvel, there's no room for anything else.

But, you can get modern non-Rifa caps that are the same size or smaller than the originals... I used them in my 8160A Pulse Gen (Along with everything else), that was one tight PSU module...

[Cerebus]

What.. I think you did that, I think that has become the most commonly used phrase by BMW, Volvo and Audi drivers at least here in the UK 

How could any of those three things be caused by driving a BMW? On the other hand I can quite understand how someone might want to throw themselves under a Škoda so that they didn't have to look at it for even a few seconds more, or stop immediately, turn their back and phone for emergency emotional support, or turn around to go and arrest someone for indecent (motor) exposure. 

[bd139]

My actual 2022 top most played on Apple Music is embarrassing so I won’t post it here 

All the Best compilation from Engelbert Humperdinck, Barry Manilow and Dean Martin¹?

 


¹ covered by Leo Moracchioli

Worse

https://youtu.be/rRncgJhNf-k

Click on this link at your own risk!

I hear that the Musician's Union have issued a fatwa against you just for posting that link.

Compare to...