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);

}
});
}