Its maximum absolute error is about ? 3g and maximum relative error is only about 0 . 4 % . evapotranspiration of tomato measured by our apparatus in laboratory during a consecutive period presents very well its change in reality 其测定值能较好地反映植物在短?段内的蒸散变化情况,是一种比较方便实用的测定盆栽植物蒸散的仪器。