DC power supply and DMM - advice and questions - Page 1
Forum section: electronics / beginners

author: lambac
author_rank: Newbie
timestamp: April 23, 2024, 02:37:34 pm
content: I'm a university chemistry researcher and my current project involves more electrical work than I am typically used to.I need to purchase a DC power supply and a DMM, but am a bit lost in terms of options, capabilities and best practices.Would anyone have any recommendations?As this project is based around the building and testing of a bench-top system, the bosses suggested that I future-proof my power supply and DMM purchases.My budget for a DC power supply and DMM are approximately €2000/$2100 USD/£1700, but there is a bit of flexibility here.Both the DC power supply and DMM need to be able to connect to a computer for data logging.At the moment I work under 30 V, (limited by the power supply) but in the future I could be running closer to 200-500V, or possibly more, depending on what the budget allows.In terms of a DMM, something with multiple channels (at least 4) would be ideal.Something like the Siglent SDM3055-SC looked promising, but when using the scanner card the voltage across each channel is 110 V max, rather than the 1000V from the front panel input. I also don't need 12 channels.If a single DMM like this can't be found, I can always use multiple DMMs?Any suggestions would be greatly appreciated.

author: jwet
author_rank: Frequent Contributor
timestamp: April 24, 2024, 02:51:44 pm
content: I'll try to give some guidance. These are actually pretty unusual requirements. 95% of power supplies are sub 30v and 99% of DMM's are single channel. You didn't talk at all about your application or any detailed needs. Future proofing can be lead to compromises and who know about the future.Some Questions for you to ponder-1. On the DMM. Resolution and accuracy requirements- how many digits basically and basic accuracy?. Long term accuracy might be important if you doing things like logging- most DMM's in electronics are used for single measurements. Is it all just DC volts? Generally pretty easy. Besides volts, what other parameters do you want to measure? Environment- lab only or sheltered outdoors, etc. Type of computer interface- options are IEEE-488- legacy but still very popular and well supported, USB- point to point, Ethernet- growing and RS-232- legacy and shrinking. USB or ethernet are probably preffered- USB must be isolated.2. For your DMM needs, you might want to consider a solid single channel benchtop instrument like the Sigilent and a Data Logger for you multichannel needs. The 100V Sigilent might be a good bet if you get a little inventive. The HV input spec might be tough to meet but you could make or buy a 10/1 divider for those cases over 100v. A DC divider is just a pair of good resistors- ac is a bit more complex, but not bad. Any EE grad student should be able to whip something up for a case of beer.3. On the power supply- you'll probably want two power supplies. A grunty 30v unit- perhaps 2A output unit. Dual output is a common requirement. If you find something you like, consider buying two. See if you really need a computer I/F, this can add cost. Also look at accuracy and resolution= its not difficult to get 10 mV of resolution- more gets expensive. Do you need current limiting, how precises? Think about how much noise you can tolerate on the outputs. What are you powering? Switching supplies are smaller and more powerful for the money but are a bit noisier. Linear supplies are quiet but get bulky over about 100W (30v 3a, etc).4. On the HVPS, decide how much current you need. Only 100 mA at 500v is 50W- this is also a potentially dangerous piece of gear- a few mA at 500v is enough to get a lethal shock. Go through your needs as above. There is much less selection. Consider looking around for something used or from another department, etc.5. Save some of your budget for test leads and interconnect stuff and possibly software to automate things. The meter will come with basic leads but consider buying an assortment of pomona banana to banana leads in red and black and maybe green and yellow at 1 meter and 2 meter lengths, these can be a bit expensive ($25/pair). Get some alligator and other connector assemblies compatible with standard bananas (4 mm) Get a quality power strip with surge and some filtering. Cabling for your computer interface- hubs, switches, etc.Good luck. We can iterate some if you have questions- I'm sure others will chime in now that I've broken the ice.