HighCharts 后台加载数据的时候去掉默认的 series

var chart;

var options = {
    chart: {
        renderTo: 'container',
        type:'line'
    },
    title: {
        text: '历史趋势时序图',
        x: -20 //center
    },
    xAxis: {
        events : {afterSetExtremes : loadDate },
        categories: []
    },
    yAxis: {
        title: { text: '测点峰值历史趋势' },
        min: 0,
        max: 100
    }
    //series: [{}]
};

$(document).ready(function(){
    // 获取测点数据
    loadSensor();

    var series = {
        yAxis: 0,
        name: "默认测点"
    };//这里是关键

    chart = new Highcharts.Chart(options);
    chart.addSeries(series);

    $("#btn_sure").click(function(){
        loadDate();

    });

    // 时间设置
    jQuery('#startDate, #endDate').datetimepicker({
        timeFormat: "hh:mm:ss",
        dateFormat: "yy-mm-dd"
    });
});

// 获取数据
    function loadDate() {

        var startDate = $.trim($("#startDate").val());
        var endDate = $.trim($("#endDate").val());
        var sensor = $.trim($("#sensor").val());
        chart.showLoading('正在加载数据...');

        $.ajax({
            url : 'jsonDiagno/jsondiagno_history.do?startDate='+startDate+'&endDate='+endDate+'&sensor='+encodeURI(encodeURI(sensor)),
            type : 'POST',
            dataType : 'json',
            contentType: "application/x-www-form-urlencoded; charset=utf-8", 
            success : function(data) {

                var series = {
                    yAxis: 0,
                    name: sensor,
                    data: data.rows
                };//加载数据的时候把之前的覆盖掉

                chart = new Highcharts.Chart(options);
                chart.addSeries(series);

            }
        });
    }

1. 初始化的时候

2. 加载数据的时候