function onRefresh(chart) {
    $.ajax({
        url: 'api/measurement/?format=json',
        data: {
            'datetime': Date.now()
        },
        dataType: 'json',
        success: function(data){
            data.forEach(function(d) {
                chart.config.data.datasets.forEach(function(dataset) {
                    dataset.data.push({
                        x: Date.parse(d.datetime),
                        y: d.i_max
                    });
                })
            })

        }
    })
}
var color = Chart.helpers.color;
var config = {
    type: 'line',
    data: {
        datasets: [{
            label: 'Streaming Impedance chart',
            backgroundColor: color(chartColors.red).alpha(0.5).rgbString(),
            borderColor: chartColors.red,
            fill: false,
            lineTension: 0,
            borderDash: [8, 4],
            data: []
        },