Lab/bench power supplies - remote control or not? - Page 1
Forum section: electronics / general

author: jpb
author_rank: Super Contributor
timestamp: June 11, 2016, 11:13:09 am
content: I currently have a TTi PL320QMD power supply (2 x 30V/2A) which I've been very pleased with (I got it new - old stock for £160 some time ago). But I could do with another power supply for my various experiments so am thinking of buying another one but am trying to work out what features are worth paying for.My PL320QMD has four different modes (parallel/series/tracking/isolated) but I've only ever used isolated - but I guess the option to double the current or voltage is useful.It doesn't have any remote control, getting this seems to add significantly to the price so I'm inclined to not get such a feature in my new supply - my main concern is it be linear (i.e. very low noise), stable and robust with good meters for both current and voltage.But I was curious as to how much others use remote control. I can see in an industrial environment where you want to do automated test it would be very useful but for experimenting and electronic development the only application I can think of is some sort of curve tracing perhaps.Do others use pc control?

author: uncle_bob
author_rank: Unknown
timestamp: June 11, 2016, 05:13:22 pm
content: HiThe same sort of automated testing that is done on production parts is also done at the bench on prototypes. In some areas, things like voltage stability are a key design feature. You do a series of sweeps and collect data. You then compensate the circuit and repeat the process to see if you got it right or not.So, yes, it does get used on a bench. A (say) USB interface that lets you set voltage can be useful. I'd freely admit that the same interface gets used more often to measure current than it does to set anything at all.Would I pay "new" price for such a device for use on my home bench? Never ever. Do I have at lest one supply around here that will do that stuff via GPIB - yup. I never use it on home projects.Bob

author: bitseeker
author_rank: Super Contributor
timestamp: June 11, 2016, 09:24:00 pm
content: If you have or plan to have other test equipment that are remote capable, then it may make sense to have a power supply with that capability so that you can automate your testing and verification processes. The time and money you invest in the automation functionality and code writing will pay off in being able to quickly and consistently reproduce your processes.

author: jpb
author_rank: Super Contributor
timestamp: June 12, 2016, 03:40:12 pm
content: Thank you for your responses.Quote from: bitseeker on June 11, 2016, 09:24:00 pmI wondered about this, for instance I regret that my oscilloscope doesn't have remote (not without spending a fortune on buying a special plug-in card) whilst my dvms, counters and Arb Waveform generator do have computer interfaces.But for the sort of use that I have it is very useful to set an experiment going and record results to a computer but I don't really ever control the dc voltage applied. So I don't use remote control, more computer logging. The one thing I might want to do is some sort of curve trace experiment for devices which take more current than my arb can provide, but for the rare occasions that I want to do this I can probably (as a hobbyist rather than a commercial user) just do it manually. It is tedious but can be oddly therapeutic!

author: uncle_bob
author_rank: Unknown
timestamp: June 12, 2016, 03:44:55 pm
content: Quote from: jpb on June 12, 2016, 03:40:12 pmHiIf you try to do curve tracing with a conventional power supply, the results can be a bit nasty looking. Generally that sort of thing is best done with gear designed for the task. More or less, it's a good DAC followed up by a very quite amplifier. Not very efficient at all, but just what you need for getting a good plot.Bob

author: jpb
author_rank: Super Contributor
timestamp: June 12, 2016, 04:05:33 pm
content: Quote from: uncle_bob on June 12, 2016, 03:44:55 pmYes, in fact any sort of dc curve tracing will give you completely wrong results in many cases. I was just trying to imagine some sort of scenario.As an aside, my background is in semiconductor device physics and I started a small company with two others and we ended up producing a pulsed measurement instrument for semiconductors which would bias the device and then use pulses to measure the other points on the characteristic curves. The idea was to go fast enough to be faster than the time constants of the deep energy levels (eg surface levels) which would trap charge .For SiC devices in particular there could be a spectacular difference. The dc curves would be nicely spaced and imply that you could get good gain and power for a class A amp for instance, but under RF conditions there would be almost no power. Doing pulsed curve measurements showed why, charge was trapped in deep levels acting like a fixed gate voltage and all the curves collapsed together.We ended up being bought out and then later I switched to computer science as the electronics (GaAs) industry in the UK had more-or-less disappeared so I now just do electronics as a hobby when I have the time.

author: bitseeker
author_rank: Super Contributor
timestamp: June 12, 2016, 09:30:13 pm
content: It sounds like you'll be fine with regular power supplies for now. Save the money for something that'll provide more enjoyment, convenience, or other benefit to your hobby rather than spend it on a feature that requires a lot of thinking to justify. Later, if you do need a remotely controllable power supply, you can always sell the regular one(s) to help offset the cost.