DMM digit accuracy

Discussion in 'General Electronics Chat' started by Omega, Feb 24, 2009.

Feb 23, 2009
15
0
Hello
when we say DMM has an accuracy 6.5 digits or 5.5 digits what does this mean?

2. leftyretro Active Member

Nov 25, 2008
394
2
It's not an indication of accuracy directly but rather of resolution. A DVM uses a analog to digital conversion and the number of bits determines it's resolutions or number of digits it can display. A 4 digit display can only show 0-9999 counts where a 6 digit display can show 0-999999 counts.

For example a 4 digit display in voltage mode will display a 5vdc measurement as 5.000, the last digit represents millivolts, while a 6 digit display would display it as 5.00000 volts where the smallest digit represents tenths of microvolts.

The half digit part means the far left digit only goes from 0-4, so a 6 1/2 digit display can show a range of 0 to 4999999 counts.

To be able to take advantage of increased resolution the meter must have better accuracy otherwise it would just be meaningless digits hung on the right end.

Make sense?

Lefty