Test Equipment Anonymous (TEA) group therapy thread

[bd139]

Nah 75 ohms is dead for that. At least since the 70s.

[Ice-Tea]

Please, please put each other on your ignore list 

[med6753]

Who wants 75R BNCs ? 

Beardie weirdies. Erm, sorry, I meant to say "distinguished members of the amateur radio fraternity". 

You got it right the first time. Unwashed Hobos.

[mansaxel]

Who wants 75R BNCs ? 

I might -- if they're true 75Ω and not something else. Canford (british broadcast equipment supplier) used to say that old video could be done with 50Ω BNC if PAL or SD-SDI (as long as cable is modern digital video cable, like their SDV made by Draka), but HD-SDI requires true 75Ω.

Edit: But that would be for nostalgic purposes only, since my job partially deals with moving video transmission to routed IP networks.

[BU508A]

I think, I'll order next month an electronic load from Maynuo @Welectron.
This one: https://www.welectron.com/Maynuo-M9812-Electronic-Load


Anybody an idea where to get these nice 4mm banana adapters for the input jacks?

Do you really need the 300W version? I got a 150W Maynuo M9710 on Aliexpress for under €250 with free shipping. Great piece of kit. Invaluable when you are designing/testing a PSU.

McBryce.

I have here two PSUs from R&S, the NGB 70/5 and the NGB 32/10. Both can output more than 300W.
I had to repair the NGB32/10 and I'm planning to do some more PSU repairing and testing.
So the 300W version would be really nice to have. And also some voltages over 100V,
because I'd like to build some linear regulated PSUs in the 120V range.

[BU508A]

@tautech:

I think, I'll order next month an electronic load from Maynuo @Welectron.
This one: https://www.welectron.com/Maynuo-M9812-Electronic-Load

What do you think is a similar device (tech-spec wise) from Siglent?
What would you recommend?

Thank you for your answer.

Could I perhaps interest you in a Chroma load?

Thanks, those are nice units but they do not fit my specs. 60V is too low for what I need.
Btw, I had already checked out your store, I always do this on a regular basis.   

[Ice-Tea]

So, eh, 300W, right?

https://www.ebay.de/itm/Chroma-6301-mainframe-63006-Electronic-Load-Module-60V-6A-300W/143470916637?hash=item216788741d:g:f8IAAOSwM71eFJfB

 

EDIT: Eh, you beat me to it. Appologies. I'll just assume you've seen my gear in the future 

[Kosmic]

Cheap HV probe on ebay this morning. 26$

https://www.ebay.com/itm/BECKMAN-INDUSTRIAL-HV231-22-HIGH-VOLTAGE-PROBE/274689423954

[Cerebus]

Nah 75 ohms is dead for that. At least since the 70s.

Sorry, are we talking about the decade or the age of the ham? 

[med6753]

Cheap HV probe on ebay this morning. 26$

https://www.ebay.com/itm/BECKMAN-INDUSTRIAL-HV231-22-HIGH-VOLTAGE-PROBE/274689423954

I don't like the hook on the end. When measuring HV my mantra is get on and get off ASAP. With that hook you could easily get hung up. 

[Kosmic]

Cheap HV probe on ebay this morning. 26$

https://www.ebay.com/itm/BECKMAN-INDUSTRIAL-HV231-22-HIGH-VOLTAGE-PROBE/274689423954

I don't like the hook on the end. When measuring HV my mantra is get on and get off ASAP. With that hook you could easily get hung up. 

It's probably removable.

[BU508A]

That's a real beast: 4x 1000V / 30A   
A Yokogawa WT3000 Precision Power Analyzer, complete with 4 modules.



Free shipping in Germany. Yeah ...

https://www.ebay-kleinanzeigen.de/s-anzeige/yokogawa-wt3000-precision-power-analyzer-4-x-1000v-30a-modules/1670281327-168-7699

[Specmaster]

Good news.  Mouser is back up and they kept their promise to ship on Monday. In addition they upgraded the shipment to UPS next day. 


Dear Papa Smurf;

Your purchase order number 21031592 is being processed by our warehouse and will ship out on 02/22/2021

We appreciate you placing this order through our website.

You requested your order be shipped by UPS 2nd DAY AIR.
To ensure that you receive your order on the day you expected it, Mouser has upgraded your order to ship UPS NEXT DAY AIR at no additional charge to you.

You are a valued customer and we appreciate your business.
If you have any questions, comments, or if we can assist you in any way please let us know.
You can reply directly to this e-mail.


Thank you,

The Mouser Internet Sales Team
orders@mouser.com
Mouser Electronics, Inc.
A TTI Company

Only the name has been changed to protect the innocent eh? 

[Ice-Tea]

That's a real beast: 4x 1000V / 30A   
A Yokogawa WT3000 Precision Power Analyzer, complete with 4 modules.



Free shipping in Germany. Yeah ...

https://www.ebay-kleinanzeigen.de/s-anzeige/yokogawa-wt3000-precision-power-analyzer-4-x-1000v-30a-modules/1670281327-168-7699

8k? Yeah, I guess they can afford free shipping 

[Cerebus]

I think, I'll order next month an electronic load from Maynuo @Welectron.
This one: https://www.welectron.com/Maynuo-M9812-Electronic-Load

I need an electronic load. I've already not done some things because of the absence of the same, and I've got projects in the pipeline that would make good use of one. I've been looking for a second hand one for a goodly while, but so far I've come up empty. I'm close to the point where I'm considering buying new, but every time I start looking at them, like that Maynuo, I keep coming up against the prices. That Mayuno is €620 and it seems a lot for what it is. I'm having a hard time persuading myself that the price of a very good HP 34401A is worth it for an electronic load.

Is it just me, or do other people think that the prices for electronic loads are rather high in terms of "bang per buck" compared to other types of TE?

Yes,
I built my own years ago. Just a bunch of power MOSFETS in parallel on a fan cooled heatsink. Initially I just drove the gates with athe summed output of a 10 turn pot and a pulse generator (for step response) but later added a couple of op-amps for feed back. 
Picture of it testing  13.8V PSU

Yeah, I keep toying with the idea of designing and building my own. There are two things that stop me diving into it:

• Lots of metalwork. For both safety and cooling reasons this is a project that needs slapping in a decent case with well engineered cooling. In principle I'd love to do it; in practice I'm limited by the lack of, or lack of access to, metalworking facilities. I currently stretch to a pilar drill and that's about it, everything else has to be done with small hand tools, not even a small sheet metal bender/brake. This is all down to lack of space for anything more fun.
• Constant power mode. I can't figure out a good way to implement this as analogue circuitry. CV, CC and constant resistance I can, but constant power I can't. Sure digital's easy enough but (1) it's slow, (2) it doesn't feel right. If anyone knows of decent schemes for analogue control of a constant power mode I'd love to hear about them.

[med6753]

Good news.  Mouser is back up and they kept their promise to ship on Monday. In addition they upgraded the shipment to UPS next day. 


Dear Papa Smurf;

Your purchase order number 21031592 is being processed by our warehouse and will ship out on 02/22/2021

We appreciate you placing this order through our website.

You requested your order be shipped by UPS 2nd DAY AIR.
To ensure that you receive your order on the day you expected it, Mouser has upgraded your order to ship UPS NEXT DAY AIR at no additional charge to you.

You are a valued customer and we appreciate your business.
If you have any questions, comments, or if we can assist you in any way please let us know.
You can reply directly to this e-mail.


Thank you,

The Mouser Internet Sales Team
orders@mouser.com
Mouser Electronics, Inc.
A TTI Company

Only the name has been changed to protect the innocent eh? 

Who said anything about being innocent? 

[bd139]

I think, I'll order next month an electronic load from Maynuo @Welectron.
This one: https://www.welectron.com/Maynuo-M9812-Electronic-Load

I need an electronic load. I've already not done some things because of the absence of the same, and I've got projects in the pipeline that would make good use of one. I've been looking for a second hand one for a goodly while, but so far I've come up empty. I'm close to the point where I'm considering buying new, but every time I start looking at them, like that Maynuo, I keep coming up against the prices. That Mayuno is €620 and it seems a lot for what it is. I'm having a hard time persuading myself that the price of a very good HP 34401A is worth it for an electronic load.

Is it just me, or do other people think that the prices for electronic loads are rather high in terms of "bang per buck" compared to other types of TE?

Yes,
I built my own years ago. Just a bunch of power MOSFETS in parallel on a fan cooled heatsink. Initially I just drove the gates with athe summed output of a 10 turn pot and a pulse generator (for step response) but later added a couple of op-amps for feed back. 
Picture of it testing  13.8V PSU

Yeah, I keep toying with the idea of designing and building my own. There are two things that stop me diving into it:

• Lots of metalwork. For both safety and cooling reasons this is a project that needs slapping in a decent case with well engineered cooling. In principle I'd love to do it; in practice I'm limited by the lack of, or lack of access to, metalworking facilities. I currently stretch to a pilar drill and that's about it, everything else has to be done with small hand tools, not even a small sheet metal bender/brake. This is all down to lack of space for anything more fun.
• Constant power mode. I can't figure out a good way to implement this as analogue circuitry. CV, CC and constant resistance I can, but constant power I can't. Sure digital's easy enough but (1) it's slow, (2) it doesn't feel right. If anyone knows of decent schemes for analogue control of a constant power mode I'd love to hear about them.

Agree with the metalwork. That always puts me off projects of certain scale.

As for power, you could use an analogue multiplier as P=IV. Only needs one quadrant as both current and voltage sense would be positive. Bugger trying to loop compensate that for stability though 

[Robert763]

I think, I'll order next month an electronic load from Maynuo @Welectron.
This one: https://www.welectron.com/Maynuo-M9812-Electronic-Load

I need an electronic load. I've already not done some things because of the absence of the same, and I've got projects in the pipeline that would make good use of one. I've been looking for a second hand one for a goodly while, but so far I've come up empty. I'm close to the point where I'm considering buying new, but every time I start looking at them, like that Maynuo, I keep coming up against the prices. That Mayuno is €620 and it seems a lot for what it is. I'm having a hard time persuading myself that the price of a very good HP 34401A is worth it for an electronic load.

Is it just me, or do other people think that the prices for electronic loads are rather high in terms of "bang per buck" compared to other types of TE?

Yes,
I built my own years ago. Just a bunch of power MOSFETS in parallel on a fan cooled heatsink. Initially I just drove the gates with athe summed output of a 10 turn pot and a pulse generator (for step response) but later added a couple of op-amps for feed back. 
Picture of it testing  13.8V PSU

Yeah, I keep toying with the idea of designing and building my own. There are two things that stop me diving into it:

• Lots of metalwork. For both safety and cooling reasons this is a project that needs slapping in a decent case with well engineered cooling. In principle I'd love to do it; in practice I'm limited by the lack of, or lack of access to, metalworking facilities. I currently stretch to a pilar drill and that's about it, everything else has to be done with small hand tools, not even a small sheet metal bender/brake. This is all down to lack of space for anything more fun.
• Constant power mode. I can't figure out a good way to implement this as analogue circuitry. CV, CC and constant resistance I can, but constant power I can't. Sure digital's easy enough but (1) it's slow, (2) it doesn't feel right. If anyone knows of decent schemes for analogue control of a constant power mode I'd love to hear about them.

You need an analog multiplier
https://www.analog.com/en/products/analog-functions/analog-multipliers-dividers.html#

I used a heatsink and fan assembly from a bit of custom kit I scrapped.

EDIT BD types faster (but didn't give a link)

[mnementh]

Oh FFS. You're right. NOBODY want them. For ANYTHING. There, are you happy?

mnem
Who fucking cares...?

Seriously? Are we gonna pick up where we left off yesterday? Robert was merely pointing out that they are 75 ohm BNC's. Not much good for anything unless you own a cable TV company or security camera outfit.

You should feel embarrassed......you made a fool of yourself yesterday and here we are, different day, same attitude. I frankly feel embarrassed for you watching the crap fly back and forth. I think it's safe to say that many in here are beginning to think you're a whiny gash.  I suspect you don't want that.

Now step away from the keyboard, go stand in the corner, kick yourself in the ass 10 times, and come back a new person.   

If the same attitude is "FFS, stop poking me with a stick!", then yes. That is my attitude.

Does anybody really care? Is it material to the fact that it is mostly useless old gear? Was I in any way trying to be negative in anything I said up to that point?

I try very hard to contribute in a positive manner here. Sometimes I fail, sometimes I don't know what I'm talking about, sometimes I'm merely comic relief. But I also try very hard not to hold a grudge. When Robert changed the subject, I deliberately looked for something positive to contribute, without hostility or any intent of negativity. I try very hard to practice the "Non-Zero Sum" game in my everyday life.

Yes, I didn't consider that there might be 2 BNCs in the whole lot of junk there that are actually 50Ω, but is it really important? Did it really require needling me again?

I don't have a problem with being wrong. Nobody can be right all the time. And if the worst that happens in a day is a little embarrassment, it's been a damned fine day.

If I am wrong, Robert, and your intent was not just to needle me again... I am sorry for being prickly. I'll get over it. Please try to do the same.

mnem
*flup!*

[ch_scr]

[...]
 If anyone knows of decent schemes for analogue control of a constant power mode I'd love to hear about them.

Propably something something analogue multiplier?

[med6753]

.......big snip....

mnem
*flup!*

Done, good boy.  Now I'm not saying we can all sit around the campfire and sing stupid songs but at least cease with cowboys and indians crap. 

The pain will go away soon and you'll be able to sit comfortably. 

[Cerebus]

As for power, you could use an analogue multiplier as P=IV. Only needs one quadrant as both current and voltage sense would be positive. Bugger trying to loop compensate that for stability though 

You need an analog multiplier
https://www.analog.com/en/products/analog-functions/analog-multipliers-dividers.html#

I used a heatsink and fan assembly from a bit of custom kit I scrapped.

EDIT BD types faster (but didn't give a link)

Yeah, the 'analogue multiplier' as the core bit of magic was self evident although I'd rather it wasn't - analogue multipliers are tricky beasts at the best of times. Where I'm at sea is the whole control loop including an analogue multiplier. I can dream up some possibilities but I've never seen anybody else's design, so I don't know whether I'm heading for likely to work (and be compensatable) territory or not.

My first guess would be measure voltage, measure current, multiply to get 'measured power', feed 'measured power' and 'set power' to a PI(D) controller controlling 'set resistance' and then an inner control loop for resistance with the inner-inner loop actually being transconductance controlled. There's already enough going on there that I don't have an instinctive feel for whether it could be made stable.

I suspect that the core truth of this is that I haven't quite managed to get my head around the whole thing yet. I'd be happier approaching the territory if I could find some examples of working systems to mentally reverse engineer - that's usually how I teach myself to do these things.

[bd139]

I got to the same point in my line of thought on the matter. Then I decided I’d just buy a load. Then I decided I didn’t need one enough to buy one. So now I have some power resistors and a calculator and make do. This quickly evolved into “stop buying things you need a load for” 

[mnementh]

I got to the same point in my line of thought on the matter. Then I decided I’d just buy a load. Then I decided I didn’t need one enough to buy one. So now I have some power resistors and a calculator and make do. This quickly evolved into “stop buying things you need a load for” 

Yeah, that was pretty much my entire line of reasoning behind the "wet coathangers of doom" DC load I fashioned for abusing server power supplies.

mnem
 

[Robert763]

Even if you want digital control of power setting an multiplying DAC is a good solution. No need for two ADC's and a bunch of math. It multiplies an analog input (can be bipolar) by the digital input. Particuarly good for ratiometric applications.
I came late to a design that was using a processor to provide a steering input to an autopilot. The required signal is ~0-12V 400Hz AC  and in phase or 180 deg out of phase with a 26V reference. It should be ratiometric to the reference. The design proposed had the reference feeding a PLL producing 409.6 kHz (1024x400Hz) that was used to clock a DDS with PWM sine shaping and amplitude control. The DDS and PWM were to be implemented on a FPGA.  Apart from complexity and difficulty in verifying the software / firmware (this is aerospace so DO-178 & DO-254) there was no ratiometric relationship. I suggested a $10 10 bit multiplying DAC whicch worked fine and saved about £50,000 in verification activity alone.