... Virtually no chance this thing has a 13+bit ADC in it... yet it's trying to do 10,000 resolution has to be a fair amount of averaging going on.
The resolution is already here for DMM's.
The
Hycon HY12P65 DMM IC has
?? A/D 18-bit at medium sample rate for 99,999 counts( bi-polar) capability.
Dream Tech's firmware is chopping this down, because crippling features is needed I guess. The 4-digit LCD display is the limiting factor to 9,999 counts.
That built-in MCU limiting factor is its 4MHz clock and 6KB code-space is pretty tight, although what's a little assembly language...
I'm tempted make a DMM with
HY3131 the analog front end with 24-bit A/D. HY3130 is 16-bit A/D for 50,000 count applications.
I'll bet the AN8002, AN8004 use the same DMM IC and firmware. People have upped the "max. counts" EEPROM number and accessed the higher resolution.
But you have to recalibrate and tronde says some True-RMS hassles. There's a few other EEPROM settings to play with.
Probably the internal voltage reference is poor and so the AN8008 went to an external Vref IC.