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EEZ Bench Box 3 - Sequel to EEZ H24005

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chriswebb:
Thought this forum would be interested in the latest product about to launch from the people who did the EEZ H24005 bench power supply:


--- Quote ---The EEZ Bench Box 3 (BB3) represents a new category of modular Test and Measurement (T&M) equipment. It provides a complete hardware and software framework that bridges the gap between – and combines the best features of – DIY hobbyist tools and professional benchtop equipment. BB3 was inspired by the EEZ H24005 power supply, which attracted many enthusiasts with its broad feature set, rich user interface, DIY friendliness, and fully open source design. BB3 will initially ship with modules that provide the same functionality as the H24005, but those modules will be slotted into a device that also delivers improved modularity, enhanced flexibility, greater capacity, and more processing power.

Our campaign will allow backers with different backgrounds, interests, and budgets to configure their BB3 however they like. Get a bare PCB set or add a custom-made enclosure. Add the three core modules, if you like, and you’ll have an Almost-Ready-To-Run (ARTR) bench box into which you can slot one of our power modules. We’re going for maximum flexibility, here.

--- End quote ---

Link to the crowd supply.

EEVBlog forum launch thread around the H24005 here.

Kean:
I have a couple of the H24005, and this new design looks quite good.
Ethernet connection should be on the rear panel IMHO.
Maybe they'll make an SMU plug-in - that would be cool.

Rerouter:
Kean. If you have thoughts on how your would implement an SMU plugin. I'm willing to lay it out. Been working piecemeal on making a 4 quadrant output stage but I am limited in knowledge as far as making it accurate enough for SMU level use cases.

Kean:

--- Quote from: Rerouter on July 12, 2019, 01:29:48 am ---Kean. If you have thoughts on how your would implement an SMU plugin. I'm willing to lay it out. Been working piecemeal on making a 4 quadrant output stage but I am limited in knowledge as far as making it accurate enough for SMU level use cases.

--- End quote ---

Not really.  I had dabbled with a design, but the precision I was aiming at was quite low.
I'm not expecting anything like the performance of a Keithley 2400 of course, but something 4 quadrant and uA or better resolution.

There is the EasySMU reference design/evalutation board from AD, but it is somewhat limited with only ±12V/±40mA
Still many occasions I think I'd find that useful.  Of course, there is no stock anywhere of the required eval board.
https://www.analog.com/en/design-center/evaluation-hardware-and-software/evaluation-boards-kits/dc2591a.html#eb-overview

Marco Reps was working on an open source SMU design called OSMU, but development on that seems to have stalled.  Not sure what his planned specs were.

Rerouter:
I would say dream for the keithley, but lets see how we can approach it economically, the main pain for me is I do not know what the input structure looks like on a SMU, I assume it is similar to an electometer but with higher bandwidth for most of the ranges, equally what voltage and current ranges are you expecting?

So we have this, the keithely 2400 output stage, nothing hard or expensive to make, and can be made a lot more flexible by using switching preregulation to reduce the total power dissipation of the output stage, instead of using all those taps, just keep it working like a bootstrap supply to keep the op amp under low power while leaving headroom for the maximum bandwidth of the transient response


Watching Dave's teardown, things of note:
5.5 digit 1uA range at the low end, for measureing, while having a 10nA output resolution so, what can we do to get close to that, e.g. maybe we have a 12-16 bit 1uA full scale range, its not impossible, just needs good layout and decent op amps. (ENOB means we probably end up closer to 3-4 digits)

The keithley does use a switching supply to make its +-225V rails, we could just do it a little more modern. tracking instead of fixed for higher output wattage

E.g. they use an AD847JN for the output op amp, in many ways that is a fairly rubbish op amp compared to what is available today. High bias currents, high offset voltage, only really has speed and gain going for it.

The ADC converter is a multi-slope converter controlled by an FPGA, now from another thread on this forum, the base of operation and op amps required for solid operation does not seem expensive, getting it to play nice over multiple decades of input may be harder, and this is where I would currently struggle, As I would probably be more willing to throw it at a self contained ADC chip, and focus on an analog control loop and managing gain with op amps.

I suppose the multislope does gain you an integrator stage, the easier way to do device power measurement would be to measure the integrator voltage set to a suitable range to get the mA from the integrated mAh allowing the measurement that so many EE's seem to struggle with when devices have uA sleep currents mixed in with mA active currents. just at X samples per second sum to bring the integrator to 0V and measure the charge to cancel, this will give you a wide range device power consuption.

Again throw some thoughts out, the man behind this project is very good at switching converters, so we may just need to step in to guide the linear and measurement side.

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