We had an ordinary bathroom scale when I first started to get serious about eating right and losing weight. I found weighing myself once a week worked pretty well, usually first thing in the morning. I did notice that it was possible to weigh myself two or three times in a row and get different results though
My wife has been a Weight Watcher participant off and on for many years and she got a digital read-out scale from WW a couple of years ago. That seems to be more accurate and will even give the same results two times in a row
There is definitely something to what JaneBrown4 says too, if you get too obsessed with a number, weight flucuations due to something as simple as more or less salt in a day's diet can appear to be derailing your progress. However when you need a size smaller clothes, you know you have made progress!