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Hacking the Siglent SDM3055 Bench DMM
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alexvg:
My Applent AT2816 is more precise for high value... But it's a specific device.

I ve done 2 simple tests (with 2-wire and 4-wire)
- a 110M resistance measurement with 4-wire display 111,7M to 112,5M over a minute
- a 110M resistance measurement with 2-wire display 111,84M to 111,87M over a minute



A funny thing I see each time...

--- Code: ---===============================================
|SIGLENT SDG800 project        /dev/pts/0
===============================================
SIGLENT Project http://         (none)
(none) login: root
Password:

Processing /etc/profile... Done
--- End code ---
(SDG800 app and data are present inside the SDM3055 firmware)
alexvg:
I'm currently working on the frequency counter... It works up to 2,2MHz... Very limited ! My UNI-T181A (half the price) works up to 60MHz.

Now I could use the frequency counter.

I've measured a maximum frequency of :
- 1Vpp : 3,1MHz square and 2,9MHz sine (Range 200mV)
- 5Vpp : 4,1MHz square and 3,9MHz sine (Range 200mV)
- 10Vpp : 5,0MHz square and 3,7MHz sine (Range 2V)
- 20Vpp : 5,0MHz square and 5,0MHz sine (Range 2V)

alexvg:
Now I've got the Capacitance measurement process.
It's possible to display a value with 5, 6, 7 or 8 digits... But the accuracy is very low...

To check capacitors, I use a LCR Applent AT2816 at 100Hz / 2V


I've done 34 measures with a list of 18 capacitors from 100pF to 10000uF.
All capacitors have been checked before and after the measure of the SDM3055 with the LCR.

Minimal error : 0,04%
Maximal error : 10,2%
Average error : 2,2%
Std Deviation : 0,0228%

The capacitance measurement of the SDM3055 is not very useful than a real LCR.
I've also checked all capacitors using a low-cost LCR (Peaktech 2170). The results are always better than the SDM3055 !
alexvg:
I've selected some components to build a pre-regulated power supply.
- A couple of LM2991/LM2941 is used to create the +/-18V (regulated later for +/-15V)
- A single BA80BC0WT is used to to create the +8V (regulated later for +5V)
- A 100V/2A/0.7V Schottky bridge rectifier (+/-15V line)
- A 40V/2A/0.5V Schottky bridge rectifier (+5V live)

The main goal is to decrease the noise of these power lines and to reduce the heat of the main regulators.
The selected LDO regulators have a switch pin which will be connected to the internal switch signal.

I also need an additionnal power supply because I'll use a LTZ1000ACH instead of the MAX6325 for the ADC voltage reference.
CDaniel:

--- Quote from: alexvg on September 22, 2019, 06:33:09 pm ---Now I've got the Capacitance measurement process.
It's possible to display a value with 5, 6, 7 or 8 digits... But the accuracy is very low...

To check capacitors, I use a LCR Applent AT2816 at 100Hz / 2V


I've done 34 measures with a list of 18 capacitors from 100pF to 10000uF.
All capacitors have been checked before and after the measure of the SDM3055 with the LCR.

Minimal error : 0,04%
Maximal error : 10,2%
Average error : 2,2%
Std Deviation : 0,0228%

The capacitance measurement of the SDM3055 is not very useful than a real LCR.
I've also checked all capacitors using a low-cost LCR (Peaktech 2170). The results are always better than the SDM3055 !

--- End quote ---

If the big error is for high value electrolytic caps it is fairly normal for a multimeter ... even two different Fluke don't display the same value and could be easily 10% off . For the simple method  of charging/discharging the cap the time is dependent on losses and current used ...
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