var temp2 = msg.AM2301.Temperature
var r = msg.AM2301.Humidity
if (temp2 !==null && !isNaN(temp2) && r !==null && !isNaN(r))
{
    var temp =  -1.0*temp2
    es = 6.112*Math.exp(-1.0*17.67*temp/(243.5 - temp));
    ed = r/100.0*es;
    eln = Math.log(ed/6.112);
var temp2 = msg.AM2301.Temperature
    td = -243.5*eln/(eln - 17.67);
    msg.dewPoint = td.toFixed(2);
}
return msg;