SMART datagrid v.1 > Classes > SignalBarCellRenderer
最左侧的格数高度。 
通过对由barRate所指定的最大高度的比例,进行指定。
默认值为0.4.
    var columns = [{
        name: "2000",
        fieldName: "2000",
        width: "100",
        renderer: {
            type: "signal",
            maximum: 10,
            barCount: 8,
            startRate: 1,
            endRate: 0.5
        },
        styles: {
            textAlignment: "far",
            shapeColor: "#080"
        }
    },
    ...
    ];
    grid.setColumns(columns);