Loarun, you'll need a calibration weight if you want to remain accurate with the cheaper scales. My first My Weigh scale was one in the $20-30 range (.1g accuracy), and I had to use the 100g weight to recalibrate several times. It only gets off calibration a little bit, but still, if you're weighing small quantities... If you're just weighing quarter ounces and up, it's not as important. When I sold it and bought a My Weigh Durascale (.01g accuracy), it came with a 50g calibration weight but I've never had to use it.
The Palmscale 7.0 is almost in the Durascale price range and comes in 700g capacity (Advance 700) and .1g accuracy, or 200g capacity (Advance 200) with .01g accuracy. Which do you need? Capacity or accuracy? Personally, in this price range I'd go for the .01g accuracy. The lower priced scales can do high capacity.
I thought that a scale would come calibrated for the factory and there would be options to calibrate a scale for a tray or dish.
Yeah they're calibrated, but apparently the higher priced models, with more expensive guts, do a better job of staying calibrated.
"Unlike other precision pocket scales, the Durscale uses TRUE 10,000 DIVISION (D-100) German-Made HBM Sensors." I don't really know what that means, but I do know as you go up in price (with a good brand), you get more sophisticated internal construction.
As for the tray calibration, that's the 'tare' feature. You place the tray/cover on the scale, press the tare button, and the scale goes back to zero.
What you get in the higher priced scales like the Palmscale and Durascale, besides better guts, is higher accuracy and more features. If weighing herb is your main use, I'd just make sure you get a top that can double as a tray with the tare feature, and then decide on capacity and .1g vs. .01g. You probably won't need the other features that come on higher priced models. Some are useful, like counting parts. Others are mostly glitz.
