Products > Test Equipment
Hacking the Siglent SDM3055 Bench DMM
Kleinstein:
I had not seen the units in the lower left corner. So the data are already after FFT and thus most of the peaks from mains hum. So mains hum seems to be a least some issue.
230 Hz is a slightly odd frequency for the extra hum. It this something like a fan or display frequency ?
The original SW seems to use the sinc4 filter with chop disabled. The window for the filtering is 40/4/ 1.3 PLC wide, but this is not simple integration over the whole time. The points at the start and end get a lower weight. Especially the very start and end have quite low weight.
It makes the comparison between data with different fitlers a bit tricky, as the readings are no all idependent, but there is still more information than skipping all the date before getting independent.
The sliding average over data with a higher rate are closer to the integration in the more classical integrating ADCs. This can have advantages, but it can also be worse in some cases. The sinc4 case is already a bit extreme. Sinc2 may some justification.
oz2cpu:
when you are rewriting the FW for 3055,
is it also possible to fix the rather wrong way the statistics avarage works ??
right now the average readout only display the same number of digits, as the main screen,
remember it sends out two more digits via remote logging and via usb logging.
other units the Keysight 34465A is claimed to be the design master for the siglent DMM series,
their statistics, average show at least one extra digit,
bu the way I also on a SDM3055 and is longtime comparing it with 34465A
I find the 3055 do contain at least one more good digit, when average 10 times,
and 2 extra digits, when averaging 200 times. for many things, I just use external data management and filtering,
I also work on adding temperature controlled regulated heater (very cheap and simple mod)
to the parts affecting drift inside the 3055, just for fun really :-)
I also got access to much better equipment by 10x and by 100x factor, wich is newly calibrated.
oz2cpu:
the SDM3055 is cheap, and nice in many ways, a perfect platform for modification / upgrade experiments
did anyone map all parts, that affect voltage read out by their temperature change to affected voltage read change ?
the most obvious is the Refferance, but also the ADC , and also other parts, like opamps ? range resistors ? input selector chips ?
do we have a have a schematic to work from ?
alexvg:
Hi,
I continue the work I've started on the SDM3055.
I'm trying to find a solution to inject my software into the SDM3055 in the simplest way possible.
I'm trying multiple hardware solution
- Ethernet via a telnet access
- Using a USB-Key (but limited to 8GB usb-key capacity)
- Using a SD-card inside the SDM-3055
I'm working on multiple solution to use my software instead of the Siglent.
- Replace all flash memory with my own data (and remove all Siglent software)
- Inject my own software as a default boot software (with an exit button to access to the original Siglent software)
Note
Siglent uses TI and GPL code. After working hard, I could use some parts already inside the Siglent SDM3055 and re-use it in my own firmware (Linux, Linaro, gcc, telnet...).
All bash scripts (from Bookwore Peng) and softwares from Siglent will never be used.
Inside the SDM3055, I've could find surprise softwares : SVN, SDG800 bin, arb, cal, fpga and other data.
I don't know if the scripts from Bookwore Peng are licenced to Siglent or not, but I've already found his code inside some webpages about the AM335x evaluation boards.
I'm working hard.
Thanks for your support.
Alexia.
tautech:
--- Quote from: alexvg on February 14, 2023, 04:47:28 pm ---I continue the work I've started on the SDM3055.
I'm trying to find a solution to inject my software into the SDM3055 in the simplest way possible.
Alexia.
--- End quote ---
Great to see you back ! :clap:
Details of Alexia's work is here:
https://www.eevblog.com/forum/testgear/hacking-the-siglent-sdm3055/
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