Using a scale in direct sunlight is a difficult situation because the temperature rise inside the scale will cause severe drift.  Using the scale in a moving vehicle is also a difficult situation as vibration will prevent stable readings and maintaining a level condition for the base may be impossible.  Some scales have features that will reduce the effects of vibration by integrating many readings and averaging them to get a result (generally called dynamic weighing).  Leveling the scale is important because the characteristic that we call weight is a result of the earth’s gravitational pull on an object, and that force has a direction (toward the earth’s center of gravity).  Even a small change in the leveling of the scales base plate will cause errors, for instance a 1 degree change of angle will cause a reduction in the weight reading of 0.016%.


Generally speaking the cautions shown in most scales user manuals, in the section on scale set up, outline those things the user must be careful to avoid.  One that is not mentioned is the use of an inverter to convert an available 12 VDC power supply to a 115 VAC power supply.  Many modern scales run on wall transformers which step the available 115 VAC down to a semi- regulated DC voltage (usually 12 VDC).  This winds up with the user taking a battery voltage from a vehicle (12 to 14 VDC unregulated and usually somewhat choppy) and converting it to 115 VAC so the wall transformer can bring it back down to a regulated 12 VDC.  This is inefficient, but usually effective.  However, there are instances where the wall transformer type power supply cannot handle the pseudo sine wave generated by the switching type DC to AC converter and causes scale problems.


If you have an application that requires that you do weighing of light objects with an accuracy of 0.01% or better, read the users manual and think about the caveats in the specifications (for instance, is the scale going to encounter humidity over 95% at any time) and the cautions that are pointed out by the manufacturer.