var $CHART$ = AmCharts.makeChart( "$CHART$", {
  "type": "gauge",
  "axes": [ {
    "axisColor": "#67b7dc",
    "axisThickness": 3,
    "endValue": 240,
    "gridInside": false,
    "inside": false,
    "radius": "100%",
    "tickColor": "#67b7dc"
  }, {
    "axisColor": "#fdd400",
    "axisThickness": 3,
    "endValue": 160,
    "radius": "80%",
    "tickColor": "#fdd400"
  } ],
  "arrows": [ {
    "color": "#67b7dc",
    "innerRadius": "20%",
    "nailRadius": 0,
    "radius": "85%"
  } ]
} );

setInterval( randomValue, 2000 );

// set random value
function randomValue() {
  var value = Math.round( Math.random() * 240 );
  $CHART$.arrows[ 0 ].setValue( value );
}