Display data of chart.js from data in html jquery

I using SignalR by Js to update my data from the database and put my data to Chart.js . But maybe my syntax goes wrong. Could you help me to edit my code? Thank you very much.

My signalR function code :

<script type="text/javascript">
    $(function () {
        //Proxy created on the fly
        var cus = $.connection.cusHub;

        //Declare a function on the job hub so the server can invoke
        cus.client.displayValue = function () {
            getData();
        };

        //Start the connection
        $.connection.hub.start();
        getData();
    });

    function getData() {
        var $tbl = $('#tblValue');
        $.ajax({
            url: $("#Get").val(),
            type: 'GET',
            datatype: 'json',
            success: function (data) {
                $tbl.empty();
                $.each(data.listCus, function (i, model) {
                    $tbl.append
                        (
                            //'<tr>' +
                            //'<td>' + model.DeviceID + '</td>' +
                            //'<td>' + model.Value + '</td>' +
                            //'</tr>'
                             model.Value
                        );
                });
            }
        });
    }
</script>

I display data in HTML by ID “tblValue” and my browser is “1000” :

                            <h2 id="tblValue"> </h2>

And I get data with getElementByID from id “tblValue” into data of Chart.js but it is null and there is nothing in my chart :

<script>
    var ctx = document.getElementById("percent-chart2");
    var my_val = document.getElementById('tblValue').innerHTML;
    var vals = parseFloat(my_val);
    if (ctx) {
            ctx.height = 209;
            var myChart = new Chart(ctx, {
                type: 'doughnut',
                data: {
                    datasets: [
                        {
                            label: "My First dataset",
                            data: [vals , vals, vals ],
                            backgroundColor: [
                                '#00b5e9',
                                '#fa4251',
                                '#006400'
                            ],
                            hoverBackgroundColor: [
                                '#00b5e9',
                                '#fa4251',
                                '#006400'
                            ],
                            borderWidth: [
                                0, 0, 0
                            ],
                            hoverBorderColor: [
                                'transparent',
                                'transparent',
                                'transparent'
                            ]
                        }
                    ],
                    labels: [
                        'STATION 1',
                        'STATION 2',
                        'STATION 3'
                    ]
                },
                options: {
                    maintainAspectRatio: false,
                    responsive: true,
                    cutoutPercentage: 87,
                    animation: {
                        animateScale: true,
                        animateRotate: true
                    },
                    legend: {
                        display: false,
                        position: 'bottom',
                        labels: {
                            fontSize: 14,
                            fontFamily: "Poppins,sans-serif"
                        }

                    },
                    tooltips: {
                        titleFontFamily: "Poppins",
                        xPadding: 15,
                        yPadding: 10,
                        caretPadding: 0,
                        bodyFontSize: 16,
                    }
                }
            });
        }
</script>

I haven’t learned about web building but my thesis relates to it. So I really need your support. Please help me.