Household digital scales are fine. Mine weigh to the 100ml. I test mine using 2lt softdrink or 3lt milk bottles. I wouldnt use the non digital scales as they can be hard to read and dont often have marks for 100g. All the types I have seen only measure to the 500g, which in my opinion, is not accurate enough.
Another way I test mine, is if I go in centre for Dx, I note what their scales say, then weigh myself when I get home. I then calculate what my UF was, and compare the two weight measurements for accuracy. Quite often they might be a kilo or two different, but if the UF is the same, then your fine.
To be even more podantic lol If I got in-centre, I weigh myself on my scales before I walk out the door, then weigh myself when I get there, and take note of the diferences in the scales. I now know the in-centre scales are about 1 kilo more than mine, so I am glad I checked, otherwise I would be going home 1lt over my dry weight!