Suggestions for a homemade DAQ alternative? - Page 1
Forum section: electronics / testgear

author: nightfire
author_rank: Frequent Contributor
timestamp: October 24, 2020, 11:42:53 pm
content: Situation: I am in the process of building my bench@home. Due to some space restrictions, I also have to opt for possibly small equipment that fits on that bench or in a small storage cabinet besides.What I want to do: My electronics tinkering will involve the combination of photography with the electronic stuff behind that, like choosing good batteries for cameras, flashes, LED lights.By checking characteristics of batteries, I basically will do some subset of the cool stuff HJK does, but with slightly different audience.So for the beginning, I do want to begin with some good quality stuff to form the core of my bench, like a DMM and tools, and to add high-quality components later on.I would need some way do some logging of measured values over time. My DMM is an Agilent U1272, so I would have some initial logging capability. But I would need to record Voltage, Current, and preferrably Temperature twice (ambient and on battery surface)What I therefore need, is some way to do some data acquisition. I seriously thought at one point to get a Siglent 3055 with scanner card or similar solutions, but the price tag in combination with some reported bugs regarding logging (and freezes) kept me away from buying it.I also had some looks for USB solutions like Picotech, Meilhaus Redlab, Red Pitaya or the Digilent Analog Discovery- which should suit my needs, if used correctly.As I also like to use a non-Windows computer (preferrably FreeBSD, maybe Linux on something like a RasPi), driver compatibility is also of interest. I also don't mind to have some devices do their own logging into a .CSV file on a USB stick or output via RS232 With this kind of serial logging I am familiar and can put some terminal application behind that- data aggregation with some software like HJK/Test Controller is nice, but no killer feature, as I could put them together later on with some kind of scripts, or maybe I use some fancy stuff like MRTG for that ;-)Anyway, I would need at least 4 inputs. Voltage inputs should be sufficient, as I could use some current converters like the µcurrent Gold or similar devices.Any suggestions for stuff I haven't already mentioned? (Yes, a Keithley DMM7500 and DAQ card or DMM7510 are nice, but for the moment somewhat out of range...)

author: Kean
author_rank: Unknown
timestamp: October 25, 2020, 10:52:54 am
content: Maybe take a look at the LabJack. I have not used it under Linux myself, but they do have Linux support. A forum search shows some attempts at getting it running on FreeBSD, but a RasPi seems more likely to succeed.I use a couple of LabJacks (standard and OEM versions) for extended (multiple day) datalogging jobs like battery charge/dicharge cycles with multiple channels of voltage, current, and temperature. They sell various add-on boards, but I typically I make up my own proto PCB for a data logging scenario using an appropriate current sensor like an ACS723, and for temperature LM34's.The Windows LabJack application make it easy to put in formulas for any required conversion. I like that I can see the converted value in real time, but you can obviously do that later on the CSV data, or via your own code.I use equipment like an Agilent 34970A DAQ, and USB or networked connected gear from Keysight/R&S/ITech (multimeters, AC/DC power supplies, DC loads) for more complex data logging and simulation, but the LabJack works great for a lot of simpler jobs.

author: bikeNomad
author_rank: Contributor
timestamp: October 25, 2020, 05:09:16 pm
content: I'd second @Kean 's suggestion of the LabJack. We have several, and often use them under Linux for test bench setups, including battery life tests. The interface is simple, and they have good Python libraries to run the LabJack.Also agree about the Agilent 34970A (or the Keysight DAQ970A) for more complicated jobs.

author: nightfire
author_rank: Frequent Contributor
timestamp: October 31, 2020, 10:56:08 pm
content: Ok, just got a used Labjack U6 off of german ebay- lets hope that little puppy arrives in reasonable condition ;-)I will have a look and then we will see if everything works out like I hope...Now I only need to get my U1272A calibrated (at least compared against another freshly calabrated DMM) and I should be good to go, so that i can check if the Labjack outputs reasonable values...

author: Kean
author_rank: Unknown
timestamp: November 01, 2020, 12:47:12 am
content: Cool. It would be great if you can report back how you go. Will try help if you have any questions.

author: nightfire
author_rank: Frequent Contributor
timestamp: November 03, 2020, 10:04:16 pm
content: Ok, my U6 arrived, and after downloading and installing the latest drivers from the manufacturer (and updating firmware) a short test with an AA battery worked well so far.For those in Europe: On german ebay there is another U6 from the same seller for less then 100 € - 184505841549I probably will be able to play a bit more at the weekend, and will see what a penguin (or daemon...) will want to recognize...