Workbench Wednesdays 53: How Advanced Power Supply Functions Work featuring the B&K 9140

Sure. But the element14 Community is much larger than just hobbyists and makers.

When I'm asked to do videos that target professional members, I do my best to show off capabilities important to them while putting the tool in a context for everyone.

I always think of it like the TV show Top Gear. (In concept, not production value.) As someone who cannot afford a supercar, I still enjoyed watching the segments on them.

In this case, I mentioned two different scenarios when you would consider this power supply. One of them was when developing a high-end FPGA-based board. If you're working on a product design that contains a $100 FPGA then a power supply in this class is a small purchase in the overall development suite.

While these types of devices are chalked with features, the cost is well outside the budgets of makers and hobbiest that build their entire lab for $1800.

Additional content that would assist those new to the disciple is where this type of device would fit.  In other words "The functions in this device are not required until..."  The same goes for all the major instruments found in a lab. 

To go along with the high-end equipment presentation would be affordable, quality equipment that would be a good initial investment for those starting out, without selling their left kidney, that would enable those indivduals to go far in thier electronics journey.  Instead of a $500 Fluke DMM perhaps an Aneng 870 or an EEVBLOG DMM would suffice until a specific point of project sophstication is achieved.

These suggestions would widen the audience and permeation of this type of content.  Most folks outside of owning their own lab could would find an $1800 power supply financial impractical and functionally excessive.  Do use cases for such levels of equipment exist?  Absolutely, but an 18-inch drill press with a 5HP motor is not always required to create a respectable hole in a piece of lumber.

Your time and consideration is greatly appreciated.

Great video!

I have an older BK Precision supply, model BK9201, and I really like it, but it's missing the modern features and multi-channel capability, which I do miss a lot. Good to see that such high power/voltage capability supplies can be feature-rich, and are available in this compact standard BK Precision form-factor!

The display is really nice too!

Okay, I misread what you wrote before. Yeah, that’s how you’d get a +/- supply from two isolated channels. 

I did the same in the video. The (-) rail from the two “positive” supplies were connected to the (+) rail or the “negative” supply. 

It sets ground in place letting the (+) and (-) be above or below 0V. 

Re: the HMC - that's interesting because that's the one that specifically states in the menu to cross-connect two channels.  I couldn't see any reference in the manual to isolation.  Perhaps I should just try it!

The TTI supply is a little confusing, in particular it's not that clear on a serial connection.  The independent mode implies that they are independent of each other but there's no ground socket on it.  This is the one I measured zero continuity between them

The HMC is definitely galvanically isolated. (I think all R&S supplies are.) FWIW, when I mention "classes" in the video, the BK 9140 and HMC are, in my opinion, in the same instrument class.

The other supply's manual is slightly confusing to me. I'd rely on DMM measurements for that one. ;)

This is a switching supply with a linear front end:  R&S®HMC804x Power Supply User Manual 

This one is a plain old linear supply: New_PL+PL-P_Series_Instruction_Manual-Iss18.pdf

I agree with your assessment. Do you have links to the datasheets/manuals for the supplies?

BTW, I think it is common for Linear supplies to do the shared +V to GND to V- connection. While SMPS are isolated.

My guess is that the flyback on the SMPS outputs naturally isolates them.

Thanks.  I've checked my supplies and none have a separate ground terminal.  

One specifically states that a negative voltage can only be generated by connecting, say, +ve ch1 to -ve ch2 and using -ve ch1 as -12v and +ch2 as +12v.  That's the way I sort of expected to do it.

The other states the channels are isolated, in effect two single output power supplies, and there is no continuity between the negative terminals.  That indicates to me I can reverse the leads at the supply as you did to get a -ve voltage.  

A nice, insightful video - it shows quite a few things I can do with my two supplies so very useful.

Yes! Almost all supplies can act as a "negative" supply. The key is that the outputs need to be (galvanically) isolated. To be isolated means they are not referenced to a common ground. (But, these supplies usually offer a ground terminal on the front panel so you CAN reference them to a common ground.)

A continuity check between the negative terminals (while the supply is off) or measuring the voltage between output channels can verify if they are isolated. On a single output supply, measure from the positive terminal to the green "Ground" terminal. You should not get the output voltage.

On a datasheet, I would just look for a mention of isolation. Galvanic isolation means the outputs are physically separated in some way.